pdf_parser 0.1.0

PDF parser
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use crate::{
    catalog::assert_len,
    data_structures::Matrix,
    error::PdfResult,
    function::Function,
    objects::{Dictionary, Object},
    Resolve,
};

/// In Type 1 (function-based) shadings, the colour at every point in the domain is defined by a specified
/// mathematical function. The function need not be smooth or continuous. This type is the most general of the
/// available shading types and is useful for shadings that cannot be adequately described with any of the other
/// types
#[derive(Debug)]
pub struct FunctionBasedShading {
    /// An array of four numbers [xmin xmax ymin ymax] specifying the rectangular domain of coordinates
    /// over which the colour function(s) are defined
    ///
    /// Default value: [0.0 1.0 0.0 1.0].
    domain: FunctionDomain,

    /// An array of six numbers specifying a transformation matrix mapping the coordinate space specified
    /// by the Domain entry into the shading's target coordinate space
    ///
    /// EXAMPLE To map the domain rectangle [0.0 1.0 0.0 1.0] to a 1-inch square with lower-left corner at
    /// coordinates (100, 100) in default user space, the Matrix value would be [72 0 0 72 100 100]
    matrix: Option<Matrix>,

    /// A 2-in, n-out function or an array of n 2-in, 1-out functions (where n is the number of
    /// colour components in the shading dictionary's colour space). Each function's domain shall
    /// be a superset of that of the shading dictionary. If the value returned by the function for
    /// a given colour component is out of range, it shall be adjusted to the nearest valid value
    function: Function,
}

impl FunctionBasedShading {
    pub fn from_dict(dict: &mut Dictionary, resolver: &mut dyn Resolve) -> PdfResult<Self> {
        let domain = dict
            .get_arr("Domain", resolver)?
            .map(|arr| FunctionDomain::from_arr(arr, resolver))
            .transpose()?
            .unwrap_or_default();

        let matrix = dict.get_matrix("Matrix", resolver)?;

        let function = dict.expect_function("Function", resolver)?;

        Ok(Self {
            domain,
            matrix,
            function,
        })
    }
}

#[derive(Debug)]
struct FunctionDomain {
    x_min: f32,
    x_max: f32,
    y_min: f32,
    y_max: f32,
}

impl FunctionDomain {
    pub fn from_arr(mut arr: Vec<Object>, resolver: &mut dyn Resolve) -> PdfResult<Self> {
        assert_len(&arr, 4)?;

        let y_max = resolver.assert_number(arr.pop().unwrap())?;
        let y_min = resolver.assert_number(arr.pop().unwrap())?;
        let x_max = resolver.assert_number(arr.pop().unwrap())?;
        let x_min = resolver.assert_number(arr.pop().unwrap())?;

        Ok(Self {
            x_min,
            x_max,
            y_min,
            y_max,
        })
    }
}

impl Default for FunctionDomain {
    fn default() -> Self {
        Self {
            x_min: 0.0,
            x_max: 1.0,
            y_min: 0.0,
            y_max: 1.0,
        }
    }
}