#![allow(unused_variables)]

//! Extended graphics state, for advanced graphical operation (overprint, black point control, etc.)
//!
//! Some of the operations can be done on the layer directly, but for advanced graphics,
//! you need to set the graphics state. A PDF has an internal default graphics state,
//! which can be reset to by setting `ExtendedGraphicsState::default()` as the active gs
//! dictionary. Setting a new graphics state overwrites the old one, there is no "undo".
//!
//! In order to use a graphics state, it must be added to the Pages resource dicitionary.
//! This is done by the `layer.set_graphics_state()` function, which returns a reference with the name of
//! the newly added dictionary. From inside a stream, the graphics state parameter is invoked
//! with the "gs" command using the name of the graphics state as a operator.
//! This is done using the `layer.use_graphics_state()`.
//!
//! A full graphics state change is done like this:
//!
//! ```rust,ignore
//! let mut new_state = ExtendedGraphicsState::default();
//! new_state.overprint_stroke = true;
//!
//! // it is best to put the next lines in a seperate function
//! // A PdfLayerReferences contains the indices of the page and the layer
//! // as well as a `std::sync::Weak` reference to the document.
//! // This is why you need the braces, otherwise, you'll trigger a deadlock
//! {
//!     // supposing mylayer is a PdfLayerReference
//!     let doc = mylayer.document.upgrade().unwrap();
//!     let mut doc = doc.lock().unwrap();
//!     let mut page = doc.pages.get_mut(self.page.0).unwrap();
//!
//!     // see the documentation for add_graphics_state
//!     page.add_graphics_state(new_state);
//! }
//! ```

use lopdf;
use lopdf::content::Operation;
use lopdf::Object::*;
use std::string::String;
use indices::FontIndex;
use std::collections::HashSet;
use std::collections::HashMap;

// identifiers for tracking the changed fields
pub (crate) const LINE_WIDTH: &'static str = "line_width";
pub (crate) const LINE_CAP: &'static str = "line_cap";
pub (crate) const LINE_JOIN: &'static str = "line_join";
pub (crate) const MITER_LIMIT: &'static str = "miter_limit";
pub (crate) const LINE_DASH_PATTERN: &'static str = "line_dash_pattern";
pub (crate) const RENDERING_INTENT: &'static str = "rendering_intent";
pub (crate) const OVERPRINT_STROKE: &'static str = "overprint_stroke";
pub (crate) const OVERPRINT_FILL: &'static str = "overprint_fill";
pub (crate) const OVERPRINT_MODE: &'static str = "overprint_mode";
pub (crate) const FONT: &'static str = "font";
pub (crate) const BLACK_GENERATION: &'static str = "black_generation";
pub (crate) const BLACK_GENERATION_EXTRA: &'static str = "black_generation_extra";
pub (crate) const UNDERCOLOR_REMOVAL: &'static str = "under_color_removal";
pub (crate) const UNDERCOLOR_REMOVAL_EXTRA: &'static str = "undercolor_removal_extra";
pub (crate) const TRANSFER_FUNCTION: &'static str = "transfer_function";
pub (crate) const TRANSFER_FUNCTION_EXTRA: &'static str = "transfer_function_extra";
pub (crate) const HALFTONE_DICTIONARY: &'static str = "halftone_dictionary";
pub (crate) const FLATNESS_TOLERANCE: &'static str = "flatness_tolerance";
pub (crate) const SMOOTHNESS_TOLERANCE: &'static str = "smoothness_tolerance";
pub (crate) const STROKE_ADJUSTMENT: &'static str = "stroke_adjustment";
pub (crate) const BLEND_MODE: &'static str = "blend_mode";
pub (crate) const SOFT_MASK: &'static str = "soft_mask";
pub (crate) const CURRENT_STROKE_ALPHA: &'static str = "current_stroke_alpha";
pub (crate) const CURRENT_FILL_ALPHA: &'static str = "current_fill_alpha";
pub (crate) const ALPHA_IS_SHAPE: &'static str = "alpha_is_shape";
pub (crate) const TEXT_KNOCKOUT: &'static str = "text_knockout";

/// List of many `ExtendedGraphicsState`
#[derive(Debug, Clone)]
pub struct ExtendedGraphicsStateList {
    /// Current indent level + current graphics state
    pub(crate) latest_graphics_state: (usize, ExtendedGraphicsState),
    /// All graphics states needed for this layer, collected together with a name for each one
    /// The name should be: "GS[index of the graphics state]", so `/GS0` for the first graphics state.
    pub(crate) all_graphics_states: HashMap<String, (usize, ExtendedGraphicsState)>,
}

impl Default for ExtendedGraphicsStateList {
    fn default()
    -> Self
    {
        Self {
            latest_graphics_state: (0, ExtendedGraphicsState::default()),
            all_graphics_states: HashMap::new(),
        }
    }
}

impl ExtendedGraphicsStateList {
    /// Creates a new ExtendedGraphicsStateList
    pub fn new()
    -> Self
    {
        Self::default()
    }

    /// Adds a graphics state
    pub fn add_graphics_state(&mut self, added_state: ExtendedGraphicsState)
    -> ExtendedGraphicsStateRef
    {
        let gs_ref = ExtendedGraphicsStateRef::new(self.all_graphics_states.len());
        self.all_graphics_states.insert(gs_ref.gs_name.clone(), (self.latest_graphics_state.0, added_state.clone()));
        self.latest_graphics_state = (self.latest_graphics_state.0, added_state);
        gs_ref
    }
}

impl Into<lopdf::Dictionary> for ExtendedGraphicsStateList {

    #[cfg_attr(feature = "cargo-clippy", allow(needless_return))]
    fn into(self)
    -> lopdf::Dictionary
    {
        let mut ext_g_state_resources = lopdf::Dictionary::new();

        for (name, (_, graphics_state)) in self.all_graphics_states {
            let gs: lopdf::Object = graphics_state.into();
            ext_g_state_resources.set(name.to_string(), gs);
        }

        return ext_g_state_resources;
    }
}

/// `ExtGState` dictionary
#[derive(Debug, PartialEq, Clone)]
pub struct ExtendedGraphicsState {
    /* /Type ExtGState */

    /// NOTE: We need to track which fields have changed in relation to the default() method.
    /// This is because we want to optimize out the fields that haven't changed in relation
    /// to the last graphics state. Please use only the constants defined in this module for
    /// declaring the changed fields. The way to go about this is to first convert the ExtGState
    /// into a vector of operations and then remove all operations that are unnecessary
    /// before writing the document.
    ///
    /// If you are unsure about this, please use the `.with_[field name]` method. These methods
    /// will set the `changed_fields` to the correct values. If you want to take care of this field
    /// manually: Every time you change a field on the ExtGState dicitionary, you have to add the
    /// string identifier of that field into the `changed_fields` vector.
    pub(crate) changed_fields: HashSet<&'static str>,

    /* LW float */
    /// __(Optional; PDF 1.3)__ The current line width
    pub(crate) line_width: f64,

    /* LC integer */
    /// __(Optional; PDF 1.3)__ The current line cap style
    pub(crate) line_cap: LineCapStyle,

    /* LJ integer */
    /// __(Optional; PDF 1.3)__ The current line join style
    pub(crate) line_join: LineJoinStyle,

    /* ML float */
    /// __(Optional; PDF 1.3)__ The miter limit (see “Miter Limit” on page 217).
    pub(crate) miter_limit: f64,

    /* D array */
    /// __(Optional; PDF 1.3)__ The line dash pattern, expressed as an array of the form
    /// [ dashArray dashPhase ] , where dashArray is itself an array and dashPhase is an
    /// integer (see “Line Dash Pattern” on page 217).
    pub(crate) line_dash_pattern: Option<LineDashPattern>,

    /* RI name (or ri inside a stream)*/
    /// __(Optional; PDF 1.3)__ The name of the rendering intent (see “Rendering
    /// Intents” on page 260).
    pub(crate) rendering_intent: RenderingIntent,

    /* OP boolean */
    /// __(Optional)__ A flag specifying whether to apply overprint (see Section 4.5.6,
    /// “Overprint Control”). In PDF 1.2 and earlier, there is a single overprint
    /// parameter that applies to all painting operations. Beginning with PDF 1.3,
    /// there are two separate overprint parameters: one for stroking and one for all
    /// other painting operations. Specifying an OP entry sets both parameters un-
    /// less there is also an op entry in the same graphics state parameter dictionary,
    /// in which case the OP entry sets only the overprint parameter for stroking.
    pub(crate) overprint_stroke: bool,

    /* op boolean */
    /// __(Optional; PDF 1.3)__ A flag specifying whether to apply overprint (see Section
    /// 4.5.6, “Overprint Control”) for painting operations other than stroking. If
    /// this entry is absent, the OP entry, if any, sets this parameter.
    pub(crate) overprint_fill: bool,

    /* OPM integer */
    /// __(Optional; PDF 1.3)__ The overprint mode (see Section 4.5.6, “Overprint Control”)
    /// Initial value: `EraseUnderlying`
    pub(crate) overprint_mode: OverprintMode,

    /* Font array */
    /// Font structure, expects a dictionary,
    pub(crate) font: Option<FontIndex>,

    /* BG function */
    /// __(Optional)__ The black-generation function, which maps the interval [ 0.0 1.0 ]
    /// to the interval [ 0.0 1.0 ] (see Section 6.2.3, “Conversion from DeviceRGB to
    /// DeviceCMYK”)
    pub(crate) black_generation: Option<BlackGenerationFunction>,

    /* BG2 function or name */
    /// __(Optional; PDF 1.3)__ Same as BG except that the value may also be the name
    /// Default , denoting the black-generation function that was in effect at the start
    /// of the page. If both BG and BG2 are present in the same graphics state param-
    /// eter dictionary, BG2 takes precedence.
    pub(crate) black_generation_extra: Option<BlackGenerationExtraFunction>,

    /* UCR function */
    /// __(Optional)__ The undercolor-removal function, which maps the interval
    /// [ 0.0 1.0 ] to the interval [ −1.0 1.0 ] (see Section 6.2.3, “Conversion from
    /// DeviceRGB to DeviceCMYK”).
    pub(crate) under_color_removal: Option<UnderColorRemovalFunction>,

    /* UCR2 function */
    /// __(Optional; PDF 1.3)__ Same as UCR except that the value may also be the name
    /// Default , denoting the undercolor-removal function that was in effect at the
    /// start of the page. If both UCR and UCR2 are present in the same graphics state
    /// parameter dictionary, UCR2 takes precedence.
    pub(crate) under_color_removal_extra: Option<UnderColorRemovalExtraFunction>,

    /* TR function */
    /// __(Optional)__ The transfer function, which maps the interval [ 0.0 1.0 ] to the in-
    /// terval [ 0.0 1.0 ] (see Section 6.3, “Transfer Functions”). The value is either a
    /// single function (which applies to all process colorants) or an array of four
    /// functions (which apply to the process colorants individually). The name
    /// Identity may be used to represent the identity function.
    pub(crate) transfer_function: Option<TransferFunction>,

    /* TR2 function */
    /// __(Optional; PDF 1.3)__ Same as TR except that the value may also be the name
    /// Default , denoting the transfer function that was in effect at the start of the
    /// page. If both TR and TR2 are present in the same graphics state parameter dic-
    /// tionary, TR2 takes precedence.
    pub(crate) transfer_extra_function: Option<TransferExtraFunction>,

    /* HT [dictionary, stream or name] */
    /// __(Optional)__ The halftone dictionary or stream (see Section 6.4, “Halftones”) or
    /// the name Default , denoting the halftone that was in effect at the start of the
    /// page.
    pub(crate) halftone_dictionary: Option<HalftoneType>,

    /* FL integer */
    /// __(Optional; PDF 1.3)__ The flatness tolerance (see Section 6.5.1, “Flatness Toler-
    /// ance”).
    pub(crate) flatness_tolerance: f64,

    /* SM integer */
    /// __(Optional; PDF 1.3)__ The smoothness tolerance (see Section 6.5.2, “Smooth-
    /// ness Tolerance”).
    pub(crate) smoothness_tolerance: f64,

    /* SA integer */
    /// (Optional) A flag specifying whether to apply automatic stroke adjustment
    /// (see Section 6.5.4, “Automatic Stroke Adjustment”).
    pub(crate) stroke_adjustment: bool,

    /* BM name or array */
    /// __(Optional; PDF 1.4)__ The current blend mode to be used in the transparent
    /// imaging model (see Sections 7.2.4, “Blend Mode,” and 7.5.2, “Specifying
    /// Blending Color Space and Blend Mode”).
    pub(crate) blend_mode: BlendMode,

    /* SM dictionary or name */
    /// __(Optional; PDF 1.4)__ The current soft mask, specifying the mask shape or
    /// mask opacity values to be used in the transparent imaging model (see
    /// “Source Shape and Opacity” on page 526 and “Mask Shape and Opacity” on
    /// page 550).
    ///
    /// *Note:* Although the current soft mask is sometimes referred to as a “soft clip,”
    /// altering it with the gs operator completely replaces the old value with the new
    /// one, rather than intersecting the two as is done with the current clipping path
    /// parameter (see Section 4.4.3, “Clipping Path Operators”).
    pub(crate) soft_mask: Option<SoftMask>,

    /* CA integer */
    /// __(Optional; PDF 1.4)__ The current stroking alpha constant, specifying the con-
    /// stant shape or constant opacity value to be used for stroking operations in the
    /// transparent imaging model (see “Source Shape and Opacity” on page 526 and
    /// “Constant Shape and Opacity” on page 551).
    pub(crate) current_stroke_alpha: f64,

    /* ca integer */
    /// __(Optional; PDF 1.4)__ Same as CA , but for nonstroking operations.
    pub(crate) current_fill_alpha: f64,

    /* AIS boolean */
    /// __(Optional; PDF 1.4)__ The alpha source flag (“alpha is shape”), specifying
    /// whether the current soft mask and alpha constant are to be interpreted as
    /// shape values ( true ) or opacity values ( false )
    /// true if the soft mask contains shape values, false for opacity
    pub(crate) alpha_is_shape: bool,

    /* TK boolean */
    /// __(Optional; PDF 1.4)__ The text knockout flag, which determines the behavior of
    /// overlapping glyphs within a text object in the transparent imaging model (see
    /// Section 5.2.7, “Text Knockout”).
    pub(crate) text_knockout: bool,
}

#[derive(Debug, Clone, Default)]
pub struct ExtendedGraphicsStateBuilder {
    /// Private field so we can control the `changed_fields` parameter
    gs: ExtendedGraphicsState,
}

impl ExtendedGraphicsStateBuilder {

    /// Creates a new graphics state builder
    pub fn new()
    -> Self
    {
        Self::default()
    }

    /// Sets the line width
    #[inline]
    pub fn with_line_width(mut self, line_width: f64)
    -> Self
    {
        self.gs.line_width = line_width;
        self.gs.changed_fields.insert(LINE_WIDTH);
        self
    }

    /// Sets the line cap
    #[inline]
    pub fn with_line_cap(mut self, line_cap: LineCapStyle)
    -> Self
    {
        self.gs.line_cap = line_cap;
        self.gs.changed_fields.insert(LINE_CAP);
        self
    }

    /// Sets the line join
    #[inline]
    pub fn with_line_join(mut self, line_join: LineJoinStyle)
    -> Self
    {
        self.gs.line_join = line_join;
        self.gs.changed_fields.insert(LINE_JOIN);
        self
    }

    /// Sets the miter limit
    #[inline]
    pub fn with_miter_limit(mut self, miter_limit: f64)
    -> Self
    {
        self.gs.miter_limit = miter_limit;
        self.gs.changed_fields.insert(MITER_LIMIT);
        self
    }

    /// Sets the rendering intent
    #[inline]
    pub fn with_rendering_intent(mut self, rendering_intent: RenderingIntent)
    -> Self
    {
        self.gs.rendering_intent = rendering_intent;
        self.gs.changed_fields.insert(RENDERING_INTENT);
        self
    }

    /// Sets the stroke overprint
    #[inline]
    pub fn with_overprint_stroke(mut self, overprint_stroke: bool)
    -> Self
    {
        self.gs.overprint_stroke = overprint_stroke;
        self.gs.changed_fields.insert(OVERPRINT_STROKE);
        self
    }

    /// Sets the fill overprint
    #[inline]
    pub fn with_overprint_fill(mut self, overprint_fill: bool)
    -> Self
    {
        self.gs.overprint_fill = overprint_fill;
        self.gs.changed_fields.insert(OVERPRINT_FILL);
        self
    }

    /// Sets the overprint mode
    #[inline]
    pub fn with_overprint_mode(mut self, overprint_mode: OverprintMode)
    -> Self
    {
        self.gs.overprint_mode = overprint_mode;
        self.gs.changed_fields.insert(OVERPRINT_MODE);
        self
    }

    /// Sets the font
    /// __WARNING:__ Use `layer.add_font()` instead if you are not absolutely sure.
    #[inline]
    pub fn with_font(mut self, font: Option<FontIndex>)
    -> Self
    {
        self.gs.font = font;
        self.gs.changed_fields.insert(FONT);
        self
    }

    /// Sets the black generation
    #[inline]
    pub fn with_black_generation(mut self, black_generation: Option<BlackGenerationFunction>)
    -> Self
    {
        self.gs.black_generation = black_generation;
        self.gs.changed_fields.insert(BLACK_GENERATION);
        self
    }

    /// Sets the black generation extra function
    #[inline]
    pub fn with_black_generation_extra(mut self, black_generation_extra: Option<BlackGenerationExtraFunction>)
    -> Self
    {
        self.gs.black_generation_extra = black_generation_extra;
        self.gs.changed_fields.insert(BLACK_GENERATION_EXTRA);
        self
    }

    /// Sets the undercolor removal function
    #[inline]
    pub fn with_undercolor_removal(mut self, under_color_removal: Option<UnderColorRemovalFunction>)
    -> Self
    {
        self.gs.under_color_removal = under_color_removal;
        self.gs.changed_fields.insert(UNDERCOLOR_REMOVAL);
        self
    }

    /// Sets the undercolor removal extra function
    #[inline]
    pub fn with_undercolor_removal_extra(mut self, under_color_removal_extra: Option<UnderColorRemovalExtraFunction>)
    -> Self
    {
        self.gs.under_color_removal_extra = under_color_removal_extra;
        self.gs.changed_fields.insert(UNDERCOLOR_REMOVAL_EXTRA);
        self
    }

    /// Sets the transfer function
    #[inline]
    pub fn with_transfer(mut self, transfer_function: Option<TransferFunction>)
    -> Self
    {
        self.gs.transfer_function = transfer_function;
        self.gs.changed_fields.insert(TRANSFER_FUNCTION);
        self
    }

    /// Sets the transfer extra function
    #[inline]
    pub fn with_transfer_extra(mut self, transfer_extra_function: Option<TransferExtraFunction>)
    -> Self
    {
        self.gs.transfer_extra_function = transfer_extra_function;
        self.gs.changed_fields.insert(TRANSFER_FUNCTION_EXTRA);
        self
    }

    /// Sets the halftone dictionary
    #[inline]
    pub fn with_halftone(mut self, halftone_type: Option<HalftoneType>)
    -> Self
    {
        self.gs.halftone_dictionary = halftone_type;
        self.gs.changed_fields.insert(HALFTONE_DICTIONARY);
        self
    }

    /// Sets the flatness tolerance
    #[inline]
    pub fn with_flatness_tolerance(mut self, flatness_tolerance: f64)
    -> Self
    {
        self.gs.flatness_tolerance = flatness_tolerance;
        self.gs.changed_fields.insert(FLATNESS_TOLERANCE);
        self
    }

    /// Sets the smoothness tolerance
    #[inline]
    pub fn with_smoothness_tolerance(mut self, smoothness_tolerance: f64)
    -> Self
    {
        self.gs.smoothness_tolerance = smoothness_tolerance;
        self.gs.changed_fields.insert(SMOOTHNESS_TOLERANCE);
        self
    }

    /// Sets the stroke adjustment
    #[inline]
    pub fn with_stroke_adjustment(mut self, stroke_adjustment: bool)
    -> Self
    {
        self.gs.stroke_adjustment = stroke_adjustment;
        self.gs.changed_fields.insert(STROKE_ADJUSTMENT);
        self
    }

    /// Sets the blend mode
    #[inline]
    pub fn with_blend_mode(mut self, blend_mode: BlendMode)
    -> Self
    {
        self.gs.blend_mode = blend_mode;
        self.gs.changed_fields.insert(BLEND_MODE);
        self
    }

    /// Sets the soft mask
    #[inline]
    pub fn with_soft_mask(mut self, soft_mask: Option<SoftMask>)
    -> Self
    {
        self.gs.soft_mask = soft_mask;
        self.gs.changed_fields.insert(SOFT_MASK);
        self
    }

    /// Sets the current alpha for strokes
    #[inline]
    pub fn with_current_stroke_alpha(mut self, current_stroke_alpha: f64)
    -> Self
    {
        self.gs.current_stroke_alpha = current_stroke_alpha;
        self.gs.changed_fields.insert(CURRENT_STROKE_ALPHA);
        self
    }

    /// Sets the current alpha for fills
    #[inline]
    pub fn with_current_fill_alpha(mut self, current_fill_alpha: f64)
    -> Self
    {
        self.gs.current_fill_alpha = current_fill_alpha;
        self.gs.changed_fields.insert(CURRENT_FILL_ALPHA);
        self
    }

    /// Sets the current "alpha is shape"
    #[inline]
    pub fn with_alpha_is_shape(mut self, alpha_is_shape: bool)
    -> Self
    {
        self.gs.alpha_is_shape = alpha_is_shape;
        self.gs.changed_fields.insert(ALPHA_IS_SHAPE);
        self
    }

    /// Sets the current text knockout
    #[inline]
    pub fn with_text_knockout(mut self, text_knockout: bool)
    -> Self
    {
        self.gs.text_knockout = text_knockout;
        self.gs.changed_fields.insert(TEXT_KNOCKOUT);
        self
    }

    /// Consumes the builder and returns an actual ExtendedGraphicsState
    #[inline]
    #[cfg_attr(feature = "cargo-clippy", allow(needless_return))]
    pub fn build(self)
    -> ExtendedGraphicsState
    {
        return self.gs;
    }
}

impl Default for ExtendedGraphicsState {
    /// Creates a default ExtGState dictionary. Useful for resetting
    fn default()
    -> Self
    {
        Self {
            changed_fields: HashSet::new(),
            line_width: 1.0,
            line_cap: LineCapStyle::Butt,
            line_join: LineJoinStyle::Miter,
            miter_limit: 0.0,
            line_dash_pattern: None,
            rendering_intent: RenderingIntent::RelativeColorimetric,
            overprint_stroke: false,
            overprint_fill: false,
            overprint_mode: OverprintMode::EraseUnderlying,
            font: None,
            black_generation: None,
            black_generation_extra: None,
            under_color_removal: None,
            under_color_removal_extra: None,
            transfer_function: None,
            transfer_extra_function: None,
            halftone_dictionary: None,
            flatness_tolerance: 0.0,
            smoothness_tolerance: 0.0,
            stroke_adjustment: true,
            blend_mode: BlendMode::Seperable(SeperableBlendMode::Normal),
            soft_mask: None,
            current_stroke_alpha: 1.0, /* 1.0 = opaque, not transparent*/
            current_fill_alpha: 1.0,
            alpha_is_shape: false,
            text_knockout: false,
        }
    }
}

impl Into<lopdf::Object> for ExtendedGraphicsState {

    /// Compares the current graphics state with the previous one and returns an
    /// "optimized" graphics state, meaning only the fields that have changed in
    /// comparison to the previous one are returned.
    #[cfg_attr(feature = "cargo-clippy", allow(needless_return))]
    #[cfg_attr(feature = "cargo-clippy", allow(cyclomatic_complexity))]
    #[cfg_attr(feature = "cargo-clippy", allow(string_lit_as_bytes))]
    fn into(self)
    -> lopdf::Object
    {
        use std::iter::FromIterator;
        let mut gs_operations = Vec::<(String, lopdf::Object)>::new();

        // for each field, look if it was contained in the "changed fields"
        if self.changed_fields.contains(LINE_WIDTH) {
            gs_operations.push(("LW".to_string(), self.line_width.into()));
        }

        if self.changed_fields.contains(LINE_CAP) {
            gs_operations.push(("LC".to_string(), self.line_cap.into()));
        }

        if self.changed_fields.contains(LINE_JOIN) {
            gs_operations.push(("LJ".to_string(), self.line_join.into()));
        }

        if self.changed_fields.contains(MITER_LIMIT) {
            gs_operations.push(("ML".to_string(), self.miter_limit.into()));
        }

        if self.changed_fields.contains(FLATNESS_TOLERANCE) {
            gs_operations.push(("FL".to_string(), self.flatness_tolerance.into()));
        }

        if self.changed_fields.contains(RENDERING_INTENT) {
            gs_operations.push(("RI".to_string(), self.rendering_intent.into()));
        }

        if self.changed_fields.contains(STROKE_ADJUSTMENT) {
            gs_operations.push(("SA".to_string(), self.stroke_adjustment.into()));
        }

        if self.changed_fields.contains(OVERPRINT_FILL) {
            gs_operations.push(("OP".to_string(), self.overprint_fill.into()));
        }

        if self.changed_fields.contains(OVERPRINT_STROKE) {
            gs_operations.push(("op".to_string(), self.overprint_stroke.into()));
        }

        if self.changed_fields.contains(OVERPRINT_MODE) {
            gs_operations.push(("OPM".to_string(), self.overprint_mode.into()));
        }

        if self.changed_fields.contains(CURRENT_FILL_ALPHA) {
            gs_operations.push(("CA".to_string(), self.current_fill_alpha.into()));
        }

        if self.changed_fields.contains(CURRENT_STROKE_ALPHA) {
            gs_operations.push(("ca".to_string(), self.current_stroke_alpha.into()));
        }

        if self.changed_fields.contains(BLEND_MODE) {
            gs_operations.push(("BM".to_string(), self.blend_mode.into()));
        }

        if self.changed_fields.contains(ALPHA_IS_SHAPE) {
            gs_operations.push(("AIS".to_string(), self.alpha_is_shape.into()));
        }

        if self.changed_fields.contains(TEXT_KNOCKOUT) {
            gs_operations.push(("TK".to_string(), self.text_knockout.into()));
        }

        // set optional parameters
        if let Some(ldp) = self.line_dash_pattern {
            if self.changed_fields.contains(LINE_DASH_PATTERN) {
                let pattern: lopdf::Object = ldp.into();
                gs_operations.push(("D".to_string(), pattern));
            }
        }

        if let Some(ref font) = self.font {
            if self.changed_fields.contains(FONT) {
                // let font_ref: lopdf::Object = font.into(); /* should be a reference to a font dictionary later on*/
                // gs_operations.push(("Font".to_string(), font_ref));
            }
        }

        // todo: transfer functions, halftone functions,
        // black generation, undercolor removal
        // these types cannot yet be converted into lopdf::Objects,
        // need to implement Into<Object> for them

        if self.changed_fields.contains(BLACK_GENERATION) {
            if let Some(ref black_generation) = self.black_generation {

            }
        }

        if self.changed_fields.contains(BLACK_GENERATION_EXTRA) {
            if let Some(ref black_generation_extra) = self.black_generation_extra {

            }
        }

        if self.changed_fields.contains(UNDERCOLOR_REMOVAL) {
            if let Some(ref under_color_removal) = self.under_color_removal {

            }
        }

        if self.changed_fields.contains(UNDERCOLOR_REMOVAL_EXTRA) {
            if let Some(ref under_color_removal_extra) = self.under_color_removal_extra {

           }
        }

        if self.changed_fields.contains(TRANSFER_FUNCTION) {
            if let Some(ref transfer_function) = self.transfer_function {

            }
        }

        if self.changed_fields.contains(TRANSFER_FUNCTION_EXTRA) {
            if let Some(ref transfer_extra_function) = self.transfer_extra_function {

            }
        }

        if self.changed_fields.contains(HALFTONE_DICTIONARY) {
            if let Some(ref halftone_dictionary) = self.halftone_dictionary {

            }
        }

        if self.changed_fields.contains(SOFT_MASK) {
            if let Some(ref soft_mask) = self.soft_mask {

            } else {
                gs_operations.push(("SM".to_string(), Name("None".as_bytes().to_vec())));
            }
        }

        // if there are operations, push the "Type > ExtGState"
        // otherwise, just return an empty dictionary
        if !gs_operations.is_empty() {
            gs_operations.push(("Type".to_string(), "ExtGState".into()));
        }

        let graphics_state = lopdf::Dictionary::from_iter(gs_operations);

        return Dictionary(graphics_state);
    }
}

/// A reference to the graphics state, for reusing the
/// graphics state during a stream without adding new graphics states all the time
pub struct ExtendedGraphicsStateRef {
    /// The name / hash of the graphics state
    pub(crate) gs_name: String,
}

impl ExtendedGraphicsStateRef {
    /// Creates a new graphics state reference (in order to be unique inside a page)
    #[inline]
    pub fn new(index: usize)
    -> Self
    {
        Self {
            gs_name: format!("GS{:?}", index)
        }
    }
}

/// __(PDF 1.3)__ A code specifying whether a color component value of 0
/// in a `DeviceCMYK` color space should erase that component (`EraseUnderlying`) or
/// leave it unchanged (`KeepUnderlying`) when overprinting (see Section 4.5.6, “Over-
/// print Control”). Initial value: `EraseUnderlying`
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum OverprintMode {
    /// Erase underlying color when overprinting
    EraseUnderlying, /* 0, default */
    /// Keep underlying color when overprinting
    KeepUnderlying,  /* 1 */
}

impl Into<lopdf::Object> for OverprintMode {
    fn into(self)
    -> lopdf::Object
    {
        use self::OverprintMode::*;
        match self {
            EraseUnderlying     => Integer(0),
            KeepUnderlying      => Integer(1),
        }
    }
}

/// Black generation calculates the amount of black to be used when trying to
/// reproduce a particular color.
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum BlackGenerationFunction {
    /// Regular black generation function
    ///
    /// ```rust,ignore
    /// let cyan = 1.0 - red;
    /// let magenta = 1.0 - green;
    /// let yellow = 1.0 - blue;
    /// let black = min(cyan, magenta, yellow);
    /// ```
    Default,
    /// Expects an UnderColorRemoval to be set. This will compensate
    /// the color for the added black
    ///
    /// ```rust,ignore
    /// let cyan = 1.0 - red;
    /// let magenta = 1.0 - green;
    /// let yellow = 1.0 - blue;
    /// let black = min(cyan, magenta, yellow);
    /// ```
    WithUnderColorRemoval,
}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum BlackGenerationExtraFunction {

}

/// See `BlackGenerationFunction`, too. Undercolor removal reduces the amounts
/// of the cyan, magenta, and yellow components to compensate for the amount of
/// black that was added by black generation.
///
/// The undercolor-removal function computes the amount to subtract from each of
/// the intermediate c, m, and y values to produce the final cyan, magenta, and yellow
/// components. It can simply return its k operand unchanged, or it can return 0.0
/// (so that no color is removed), some fraction of the black amount, or even a
/// negative amount, thereby adding to the total amount of colorant.
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum UnderColorRemovalFunction {
    Default,
}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum UnderColorRemovalExtraFunction {

}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum TransferFunction {

}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum TransferExtraFunction {

}

/// In PDF 1.2, the graphics state includes a current halftone parameter,
/// which determines the halftoning process to be used by the painting operators.
/// It may be defined by either a dictionary or a stream, depending on the
/// type of halftone; the term halftone dictionary is used generically
/// throughout this section to refer to either a dictionary object or the
/// dictionary portion of a stream object. (The halftones that are defined
/// by streams are specifically identified as such in the descriptions
/// of particular halftone types; unless otherwise stated, they are
/// understood to be defined by simple dictionaries instead.)

/*
    <<
        /Type /Halftone
        /HalftoneType 1
        /Frequency 120
        /Angle 30
        /SpotFunction /CosineDot
        /TransferFunction /Identity
    >>
*/

/// Deserialized into Integer: 1, 5, 6, 10 or 16
#[derive(Debug, PartialEq, Clone)]
pub enum HalftoneType {
    /// 1: Defines a single halftone screen by a frequency, angle, and spot function
    Type1(f64, f64, SpotFunction),
    /// 5: Defines an arbitrary number of halftone screens, one for each colorant or
    /// color component (including both primary and spot colorants).
    /// The keys in this dictionary are names of colorants; the values are halftone
    /// dictionaries of other types, each defining the halftone screen for a single colorant.
    Type5(Vec<HalftoneType>),
    /// 6: Defines a single halftone screen by a threshold array containing 8-bit sample values.
    Type6(Vec<u8>),
    /// 10: Defines a single halftone screen by a threshold array containing 8-bit sample values,
    /// representing a halftone cell that may have a nonzero screen angle.
    Type10(Vec<u8>),
    /// 16: __(PDF 1.3)__ Defines a single halftone screen by a threshold array containing 16-bit
    /// sample values, representing a halftone cell that may have a nonzero screen angle.
    Type16(Vec<u16>),
}

impl HalftoneType {
    /// Get the identifer integer of the HalftoneType
    pub fn get_type(&self)
    -> i64
    {
        use self::HalftoneType::*;
        match *self {
            Type1(_, _, _) => 1,
            Type5(_) => 5, /* this type does not actually exist, todo */
            Type6(_) => 6,
            Type10(_) => 10,
            Type16(_) => 16,
        }
    }

    pub fn into_obj(self)
    -> Vec<lopdf::Object>
    {
        use std::iter::FromIterator;
        vec![Dictionary(lopdf::Dictionary::from_iter(vec![
                    ("Type", "Halftone".into()),
                    ("HalftoneType", self.get_type().into())
            ]))]
    }
}

/// Spot functions, Table 6.1, Page 489 in Pdf Reference v1.7
/// The code is pseudo code, returning the grey component at (x, y).
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum SpotFunction {
    /// `1 - (pow(x, 2) + pow(y, 2))`
    SimpleDot,
    /// `pow(x, 2) + pow(y, 2) - 1`
    InvertedSimpleDot,
    /// `(sin(360 * x) / 2) + (sin(360 * y) / 2)`
    DoubleDot,
    /// `- ((sin(360 * x) / 2) + (sin(360 * y) / 2))`
    InvertedDoubleDot,
    /// `(cos(180 * x) / 2) + (cos(180 * y) / 2)`
    CosineDot,
    /// `(sin(360 x (x / 2)) / 2) + (sin(360 * y) / 2)`
    Double,
    /// `- ((sin(360 x (x / 2)) / 2) + (sin(360 * y) / 2))`
    InvertedDouble,
    /// `- abs(y)`
    Line,
    /// `x`
    LineX,
    /// `y`
    LineY,
    /// ```rust,ignore
    /// if (abs(x) + abs(y) <= 1 {
    ///     1 - (pow(x, 2) + pow(y, 2))
    /// } else {
    ///     pow((abs(x) - 1), 2) + pow((abs(y) - 1), 2) - 1
    /// }
    /// ```
    Round,
    /// ```rust,ignore
    /// let w = (3 * abs(x)) + (4 * abs(y)) - 3;
    ///
    /// if w < 0 {
    ///     1 - ((pow(x, 2) + pow((abs(y) / 0.75), 2)) / 4)
    /// } else if w > 1 {
    ///     pow((pow((1 - abs(x), 2) + (1 - abs(y)) / 0.75), 2) / 4) - 1
    /// } else {
    ///     0.5 - w
    /// }
    /// ```
    Ellipse,
    /// `1 - (pow(x, 2) + 0.9 * pow(y, 2))`
    EllipseA,
    /// `pow(x, 2) + 0.9 * pow(y, 2) - 1`
    InvertedEllipseA,
    /// `1 - sqrt(pow(x, 2) + (5 / 8) * pow(y, 2))`
    EllipseB,
    /// `1 - (0.9 * pow(x, 2) + pow(y, 2))`
    EllipseC,
    /// `0.9 * pow(x, 2) + pow(y, 2) - 1`
    InvertedEllipseC,
    /// `- max(abs(x), abs(y))`
    Square,
    /// `- min(abs(x), abs(y))`
    Cross,
    /// `(0.9 * abs(x) + abs(y)) / 2`
    Rhomboid,
    /// ```rust,ignore
    /// let t = abs(x) + abs(y);
    /// if t <= 0.75 {
    ///     1 - (pow(x, 2) + pow(y, 2))
    /// } else if t < 1.23 {
    ///     1 - (0.85 * abs(x) + abs(y))
    /// } else {
    ///     pow((abs(x) - 1), 2) + pow((abs(y) - 1), 2) - 1
    /// }
    /// ```
    Diamond,
}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum BlendMode {
    Seperable(SeperableBlendMode),
    NonSeperable(NonSeperableBlendMode),
}

impl Into<lopdf::Object> for BlendMode {
    fn into(self)
    -> lopdf::Object {
        use self::BlendMode::*;
        use self::SeperableBlendMode::*;
        use self::NonSeperableBlendMode::*;

        let blend_mode_str = match self {
            Seperable(s) => {
                match s {
                    Normal => "Normal",
                    Multiply => "Multiply",
                    Screen => "Screen",
                    Overlay => "Overlay",
                    Darken => "Darken",
                    Lighten => "Lighten",
                    ColorDodge => "ColorDodge",
                    ColorBurn => "ColorBurn",
                    HardLight => "HardLight",
                    SoftLight => "SoftLight",
                    Difference => "Difference",
                    Exclusion => "Exclusion",
                }
            },
            NonSeperable(n) => {
                match n {
                    Hue => "Hue",
                    Saturation => "Saturation",
                    Color => "Color",
                    Luminosity => "Luminosity",
                }
            }
        };

        Name(blend_mode_str.as_bytes().to_vec())
    }
}

/// PDF Reference 1.7, Page 520, Table 7.2
/// Blending modes for objects
/// In the following reference, each function gets one new color (the thing to paint on top)
/// and an old color (the color that was already present before the object gets painted)
///
/// The function simply notes the formula that has to be applied to (`color_new`, `color_old`) in order
/// to get the desired effect. You have to run each formula once for each color channel.
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum SeperableBlendMode {
    /// Selects the source color, ignoring the old color. Default mode.
    ///
    /// `color_new`
    Normal,
    /// Multiplies the old color and source color values
    /// Note that these values have to be in the range [0.0 to 1.0] to work.
    /// The result color is always at least as dark as either of the two constituent
    /// colors. Multiplying any color with black produces black; multiplying with white
    /// leaves the original color unchanged.Painting successive overlapping objects with
    /// a color other than black or white produces progressively darker colors.
    ///
    /// `color_old * color_new`
    Multiply,
    /// Multiplies the complements of the old color and new color values, then
    /// complements the result
    /// The result color is always at least as light as either of the two constituent colors.
    /// Screening any color with white produces white; screening with black leaves the original
    /// color unchanged. The effect is similar to projecting multiple photographic slides
    /// simultaneously onto a single screen.
    ///
    /// `color_old + color_new - (color_old * color_new)`
    Screen,
    /// Multiplies or screens the colors, depending on the old color value. Source colors
    /// overlay the old color while preserving its highlights and shadows. The old color is
    /// not replaced but is mixed with the source color to reflect the lightness or darkness
    /// of the old color.
    ///
    /// TLDR: It's the inverse of HardLight
    ///
    /// ```rust,ignore
    /// if color_old <= 0.5 {
    ///     Multiply(color_new, 2 x color_old)
    /// } else {
    ///     Screen(color_new, 2 * color_old - 1)
    /// }
    /// ```
    Overlay,
    /// Selects the darker one of two colors.The old color is replaced with the
    /// new color where the new color is darker; otherwise, it is left unchanged.
    ///
    /// `min(color_old, color_new)`
    Darken,
    /// Selects the lighter one of two colors. The old color is replaced with the
    /// new color where the new color is lighter; otherwise, it is left unchanged.
    ///
    /// `max(color_old, color_new)`
    Lighten,
    /// Brightens the backdrop color to reflect the source color. Painting with
    /// black produces no changes.
    ///
    /// ```rust,ignore
    /// if color_new < 1 {
    ///     min(1, color_old / (1 - color_new))
    /// } else {
    ///     1
    /// }
    /// ```
    ColorDodge,
    /// Darkens the backdrop color to reflect the source color. Painting with
    /// white produces no change.
    ///
    /// ```rust,ignore
    /// if color_new > 0 {
    ///     1 - min(1, (1 - color_old) / color_new))
    /// } else {
    ///     0
    /// }
    /// ```
    ColorBurn,
    /// Multiplies or screens the colors, depending on the source color value. The effect is
    /// similar to shining a harsh spotlight on the old color. It's the inverse of Screen.
    ///
    /// ```rust,ignore
    /// if color_new <= 0.5 {
    ///     Multiply(color_old, 2 x color_new)
    /// } else {
    ///     Screen(color_old, 2 * color_new - 1)
    /// }
    /// ```
    HardLight,
    /// Darkens or lightens the colors, depending on the source color value.
    /// The effect is similar to shining a diffused spotlight on the backdrop.
    ///
    /// ```rust,ignore
    /// if color_new <= 0.5 {
    ///     color_old - ((1 - (2 * color_new)) * color_old * (1 - color_old))
    /// } else {
    ///     let mut dx_factor = color_old.sqrt();
    ///     if color_old <= 0.25 {
    ///         dx_factor = (((16 * color_old - 12) * color_old) + 4) * color_old;
    ///     }
    ///     color_old + ((2 * color_new) - 1) * (dx_factor - color_old)
    /// }
    /// ```
    SoftLight,
    /// Subtracts the darker of the two constituent colors from the lighter color
    /// Painting with white inverts the backdrop color; painting with black produces no change.
    ///
    /// `abs(color_old - color_new)`
    Difference,
    /// Produces an effect similar to that of the Difference mode but lower in contrast.
    /// Painting with white inverts the backdrop color; painting with black produces no change.
    ///
    /// `color_old + color_new - (2 * color_old * color_new)`
    Exclusion,
}

/// Since the nonseparable blend modes consider all color components in combination, their
/// computation depends on the blending color space in which the components are interpreted.
/// They may be applied to all multiple-component color spaces that are allowed as blending
/// color spaces (see Section 7.2.3, “Blending Color Space”).
///
/// All of these blend modes conceptually entail the following steps:
///
/// 1. Convert the backdrop and source colors from the blending color space to an intermediate
///    HSL (hue-saturation-luminosity) representation.
/// 2. Create a new color from some combination of hue, saturation, and luminosity components
///    selected from the backdrop and source colors.
/// 3. Convert the result back to the original (blending) color space.
///
/// However, the formulas given below do not actually perform these conversions. Instead,
/// they start with whichever color (backdrop or source) is providing the hue for the result;
/// then they adjust this color to have the proper saturation and luminosity.
///
/// ### For RGB color spaces
///
/// The nonseparable blend mode formulas make use of several auxiliary functions. These
/// functions operate on colors that are assumed to have red, green, and blue components.
///
/// ```rust,ignore
/// # #[macro_use] extern crate printpdf;
/// # use printpdf::Rgb;
/// # use printpdf::glob_macros::*;
/// # fn main() { /* needed for testing*/ }
/// fn luminosity(input: Rgb) -> f64 {
///     0.3 * input.r + 0.59 * input.g + 0.11 * input.b
/// }
///
/// fn set_luminosity(input: Rgb, target_luminosity: f64) -> Rgb {
///     let d = target_luminosity - luminosity(input);
///     Rgb {
///         r: input.r + d,
///         g: input.g + d,
///         b: input.b + d,
///         icc_profile: input.icc_profile,
///     }
/// }
///
/// fn clip_color(mut input: Rgb) -> Rgb {
///
///     let lum = luminosity(input);
///
///     let mut cur_r = (input.r * 1000.0) as i64;
///     let mut cur_g = (input.g * 1000.0) as i64;
///     let mut cur_b = (input.b * 1000.0) as i64;
///
///     /// min! and max! is defined in printpdf/src/glob_macros.rs
///     let mut min = min!(cur_r, cur_g, cur_b);
///     let mut max = max!(cur_r, cur_g, cur_b);
///
///     let new_min = (min as f64) / 1000.0;
///     let new_max = (max as f64) / 1000.0;
///
///     if new_min < 0.0 {
///         input.r = lum + (((input.r - lum) * lum) / (lum - new_min));
///         input.g = lum + (((input.g - lum) * lum) / (lum - new_min));
///         input.b = lum + (((input.b - lum) * lum) / (lum - new_min));
///     } else if new_max > 1.0 {
///         input.r = lum + ((input.r - lum) * (1.0 - lum) / (new_max - lum));
///         input.g = lum + ((input.g - lum) * (1.0 - lum) / (new_max - lum));
///         input.b = lum + ((input.b - lum) * (1.0 - lum) / (new_max - lum));
///     }
///
///     return input;
/// }
///
/// fn saturation(input: Rgb) -> f64 {
///     let mut cur_r = (input.r * 1000.0) as i64;
///     let mut cur_g = (input.g * 1000.0) as i64;
///     let mut cur_b = (input.b * 1000.0) as i64;
///
///     /// min! and max! is defined in printpdf/src/glob_macros.rs
///     let mut min = min!(cur_r, cur_g, cur_b);
///     let mut max = max!(cur_r, cur_g, cur_b);
///
///     let new_min = (min as f64) / 1000.0;
///     let new_max = (max as f64) / 1000.0;
///     new_max - new_min
/// }
/// ```
///
/// ### For CMYK color spaces
///
/// The C, M, and Y components are converted to their complementary R, G, and B components
/// in the usual way. The formulas above are applied to the RGB color values. The results
/// are converted back to C, M, and Y.
///
/// For the K component, the result is the K component of Cb for the Hue, Saturation, and
/// Color blend modes; it is the K component of Cs for the Luminosity blend mode.
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum NonSeperableBlendMode {
    Hue,
    Saturation,
    Color,
    Luminosity,
}

/* RI name (or ri inside a stream)*/
/// Although CIE-based color specifications are theoretically device-independent,
/// they are subject to practical limitations in the color reproduction capabilities of
/// the output device. Such limitations may sometimes require compromises to be
/// made among various properties of a color specification when rendering colors for
/// a given device. Specifying a rendering intent (PDF 1.1) allows a PDF file to set priorities
/// regarding which of these properties to preserve and which to sacrifice.
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum RenderingIntent {
    /// Colors are represented solely with respect to the light source; no
    /// correction is made for the output medium’s white point (such as
    /// the color of unprinted paper). Thus, for example, a monitor’s
    /// white point, which is bluish compared to that of a printer’s paper,
    /// would be reproduced with a blue cast. In-gamut colors are
    /// reproduced exactly; out-of-gamut colors are mapped to the
    /// nearest value within the reproducible gamut. This style of reproduction
    /// has the advantage of providing exact color matches
    /// from one output medium to another. It has the disadvantage of
    /// causing colors with Y values between the medium’s white point
    /// and 1.0 to be out of gamut. A typical use might be for logos and
    /// solid colors that require exact reproduction across different media.
    AbsoluteColorimetric,
    /// Colors are represented with respect to the combination of the
    /// light source and the output medium’s white point (such as the
    /// color of unprinted paper). Thus, for example, a monitor’s white
    /// point would be reproduced on a printer by simply leaving the
    /// paper unmarked, ignoring color differences between the two
    /// media. In-gamut colors are reproduced exactly; out-of-gamut
    /// colors are mapped to the nearest value within the reproducible
    /// gamut. This style of reproduction has the advantage of adapting
    /// for the varying white points of different output media. It has the
    /// disadvantage of not providing exact color matches from one me-
    /// dium to another. A typical use might be for vector graphics.
    RelativeColorimetric,
    /// Colors are represented in a manner that preserves or emphasizes
    /// saturation. Reproduction of in-gamut colors may or may not be
    /// colorimetrically accurate. A typical use might be for business
    /// graphics, where saturation is the most important attribute of the
    /// color.
    Saturation,
    /// Colors are represented in a manner that provides a pleasing perceptual
    /// appearance. To preserve color relationships, both in-gamut
    /// and out-of-gamut colors are generally modified from
    /// their precise colorimetric values. A typical use might be for scanned images.
    Perceptual,
}

/* ri name */
impl RenderingIntent {
    pub fn into_stream_op(self)
    -> Vec<Operation>
    {
        use self::RenderingIntent::*;
        let rendering_intent_string = match self {
            AbsoluteColorimetric => "AbsoluteColorimetric",
            RelativeColorimetric => "RelativeColorimetric",
            Saturation => "Saturation",
            Perceptual => "Perceptual",
        };

        vec![ Operation::new("ri", vec![ Name(rendering_intent_string.as_bytes().to_vec()) ]) ]
    }
}

/* RI name , only to be used in graphics state dictionary */
impl Into<lopdf::Object> for RenderingIntent {
    /// Consumes the object and converts it to an PDF object
    fn into(self)
    -> lopdf::Object
    {
        use self::RenderingIntent::*;
        let rendering_intent_string = match self {
            AbsoluteColorimetric => "AbsoluteColorimetric",
            RelativeColorimetric => "RelativeColorimetric",
            Saturation => "Saturation",
            Perceptual => "Perceptual",
        };

        Name(rendering_intent_string.as_bytes().to_vec())
    }
}

/// A soft mask is used for transparent images such as PNG with an alpha component
/// The bytes range from 0xFF (opaque) to 0x00 (transparent). The alpha channel of a
/// PNG image have to be sorted out.
/// Can also be used for Vignettes, etc.
/// Beware of color spaces!
/// __See PDF Reference Page 545__ - Soft masks
#[derive(Debug, PartialEq, Clone)]
pub struct SoftMask {
    /// The data to be used as a soft mask
    data: Vec<u8>,
    /// Bits per component (1 for black / white, 8 for greyscale, up to 16)
    bits_per_component: u8,
}

#[derive(Debug, PartialEq, Copy, Clone)]
pub enum SoftMaskFunction {
    // (Color, Shape, Alpha) = Composite(Color0, Alpha0, Group)
    /// In this function, the old (backdrop) color does not contribute to the result.
    /// This is the easies function, but may look bad at edges.
    GroupAlpha,
    //
    GroupLuminosity,

}
/// __See PDF Reference Page 216__ - Line join style
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum LineJoinStyle {
    /// Miter join. The outer edges of the strokes for the two segments are extended
    /// until they meet at an angle, as in a picture frame. If the segments meet at too
    /// sharp an angle (as defined by the miter limit parameter—see “Miter Limit,”
    /// above), a bevel join is used instead.
    Miter,
    /// Round join. An arc of a circle with a diameter equal to the line width is drawn
    /// around the point where the two segments meet, connecting the outer edges of
    /// the strokes for the two segments. This pieslice-shaped figure is filled in, pro-
    /// ducing a rounded corner.
    Round,
    /// Bevel join. The two segments are finished with butt caps (see “Line Cap Style”
    /// on page 216) and the resulting notch beyond the ends of the segments is filled
    /// with a triangle.
    Limit,
}

impl Into<i64> for LineJoinStyle {
    fn into(self)
    -> i64
    {
        use self::LineJoinStyle::*;
        match self {
            Miter => 0,
            Round => 1,
            Limit => 2,
        }
    }
}

impl Into<Operation> for LineJoinStyle {
    fn into(self)
    -> Operation
    {
        let line_join_num: i64 = self.into();
        Operation::new("j", vec![Integer(line_join_num)])
    }
}

impl Into<lopdf::Object> for LineJoinStyle {
    fn into(self)
    -> lopdf::Object
    {
        Integer(self.into())
    }
}

/// __See PDF Reference (Page 216)__ - Line cap (ending) style
#[derive(Debug, PartialEq, Copy, Clone)]
pub enum LineCapStyle {
    /// Butt cap. The stroke is squared off at the endpoint of the path. There is no
    /// projection beyond the end of the path.
    Butt,
    /// Round cap. A semicircular arc with a diameter equal to the line width is
    /// drawn around the endpoint and filled in.
    Round,
    /// Projecting square cap. The stroke continues beyond the endpoint of the path
    /// for a distance equal to half the line width and is squared off.
    ProjectingSquare,
}

impl Into<i64> for LineCapStyle {
    fn into(self)
    -> i64
    {
        use self::LineCapStyle::*;
        match self {
            Butt => 0,
            Round => 1,
            ProjectingSquare => 2,
        }
    }
}

impl Into<Operation> for LineCapStyle {
    fn into(self)
    -> Operation
    {
        Operation::new("J", vec![Integer(self.into())])
    }
}

impl Into<lopdf::Object> for LineCapStyle {
    fn into(self)
    -> lopdf::Object
    {
        Integer(self.into())
    }
}

/// Line dash pattern is made up of a total width
#[derive(Debug, PartialEq, Copy, Clone)]
pub struct LineDashPattern {
    /// Offset at which the dashing pattern should start, measured from the beginning ot the line
    /// Default: 0 (start directly where the line starts)
    pub offset: i64,
    /// Length of the first dash in the dash pattern. If `None`, the line will be solid (good for resetting the dash pattern)
    pub dash_1: Option<i64>,
    /// Whitespace after the first dash. If `None`, whitespace will be the same as length_1st,
    /// meaning that the line will have dash - whitespace - dash - whitespace in even offsets
    pub gap_1: Option<i64>,
    /// Length of the second dash in the dash pattern. If None, will be equal to length_1st
    pub dash_2: Option<i64>,
    /// Same as whitespace_1st, but for length_2nd
    pub gap_2: Option<i64>,
    /// Length of the second dash in the dash pattern. If None, will be equal to length_1st
    pub dash_3: Option<i64>,
    /// Same as whitespace_1st, but for length_3rd
    pub gap_3: Option<i64>,
}

impl LineDashPattern {
    /// Creates a new dash pattern
    pub fn new(offset: i64, dash_1: Option<i64>, gap_1: Option<i64>, dash_2: Option<i64>, gap_2: Option<i64>, dash_3: Option<i64>, gap_3: Option<i64>)
    -> Self
    {
        Self { offset, dash_1, gap_1, dash_2, gap_2, dash_3, gap_3 }
    }

    /// Creates a new dash pattern
    pub fn default()
    -> Self
    {
        Self { offset: 0, dash_1: None, gap_1: None, dash_2: None, gap_2: None, dash_3: None, gap_3: None }
    }
}

// conversion into a dash array for reuse in operation / gs dictionary
impl Into<(Vec<i64>, i64)> for LineDashPattern {
    #[cfg_attr(feature = "cargo-clippy", allow(never_loop))]
    #[cfg_attr(feature = "cargo-clippy", allow(while_let_loop))]
    #[cfg_attr(feature = "cargo-clippy", allow(needless_return))]
    fn into(self)
    -> (Vec<i64>, i64)
    {
        let mut dash_array = Vec::<i64>::new();

        // note: it may be that PDF allows more than 6 operators.
        // I've not seen it in practise, though

        // break as soon as we encounter a None
        loop {

            if let Some(d1) = self.dash_1 {
                dash_array.push(d1);
            } else { break; }

            if let Some(g1) = self.gap_1 {
                dash_array.push(g1);
            } else { break; }

            if let Some(d2) = self.dash_2 {
                dash_array.push(d2);
            } else { break; }

            if let Some(g2) = self.gap_2 {
                dash_array.push(g2);
            } else { break; }

            if let Some(d3) = self.dash_3 {
                dash_array.push(d3);
            } else { break; }

            if let Some(g3) = self.gap_3 {
                dash_array.push(g3);
            } else { break; }

            break;
        }

        return (dash_array, self.offset);
    }

}

impl Into<Operation> for LineDashPattern {
    fn into(self)
    -> Operation
    {
        let (dash_array, offset) = self.into();
        let dash_array_ints = dash_array.into_iter().map(Integer).collect();
        Operation::new("d", vec![Array(dash_array_ints), Integer(offset)])
    }
}

impl Into<lopdf::Object> for LineDashPattern {
    fn into(self)
    -> lopdf::Object
    {
        use lopdf::Object::*;
        let (dash_array, offset) = self.into();
        let mut dash_array_ints: Vec<lopdf::Object> = dash_array.into_iter().map(Integer).collect();
        dash_array_ints.push(Integer(offset));
        Array(dash_array_ints)
    }
}