1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
//! Common types shared between the encoder and decoder
use std::mem;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum ColorType {
    Grayscale = 0,
    RGB = 2,
    Indexed = 3,
    GrayscaleAlpha = 4,
    RGBA = 6
}

impl ColorType {
    /// Returns the number of samples used per pixel of `ColorType`
    pub fn samples(&self) -> usize {
        use self::ColorType::*;
        match *self {
            Grayscale => 1,
            RGB => 3,
            Indexed => 1,
            GrayscaleAlpha => 2,
            RGBA => 4
        }
    }
    
    /// u8 -> Self. Temporary solution until Rust provides a canonical one.
    pub fn from_u8(n: u8) -> Option<ColorType> {
        match n {
            0 | 2 | 3 | 4 | 6 => Some(unsafe { mem::transmute(n) }),
            _ => None
        }
    }
}

/// Bit depth of the png file
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
pub enum BitDepth {
    One     = 1,
    Two     = 2,
    Four    = 4,
    Eight   = 8,
    Sixteen = 16,
}

impl BitDepth {
    /// u8 -> Self. Temporary solution until Rust provides a canonical one.
    pub fn from_u8(n: u8) -> Option<BitDepth> {
        match n {
            1 | 2 | 4 | 8 | 16 => Some(unsafe { mem::transmute(n) }),
            _ => None
        }
    }
}

/// Pixel dimensions information
#[derive(Clone, Copy, Debug)]
pub struct PixelDimensions {
    /// Pixels per unit, X axis
    pub xppu: u32,
    /// Pixels per unit, Y axis
    pub yppu: u32,
    /// Either *Meter* or *Unspecified*
    pub unit: Unit,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u8)]
/// Physical unit of the pixel dimensions
pub enum Unit {
    Unspecified = 0,
    Meter = 1,
}

impl Unit {
    /// u8 -> Self. Temporary solution until Rust provides a canonical one.
    pub fn from_u8(n: u8) -> Option<Unit> {
        match n {
            0 | 1 => Some(unsafe { mem::transmute(n) }),
            _ => None
        }
    }
}

/// Frame control information
#[derive(Debug)]
pub struct FrameControl {
    /// Sequence number of the animation chunk, starting from 0
    pub sequence_number: u32,
    /// Width of the following frame
    pub width: u32,
    /// Height of the following frame
    pub height: u32,
    /// X position at which to render the following frame
    pub x_offset: u32,
    /// Y position at which to render the following frame
    pub y_offset: u32,
    /// Frame delay fraction numerator
    pub delay_num: u16,
    /// Frame delay fraction denominator
    pub delay_den: u16,
    /// Type of frame area disposal to be done after rendering this frame
    pub dispose_op: u8,
    /// Type of frame area rendering for this frame
    pub blend_op: u8,
}

/// Animation control information
#[derive(Clone, Copy, Debug)]
pub struct AnimationControl {
    /// Number of frames
    pub num_frames: u32,
    /// Number of times to loop this APNG.  0 indicates infinite looping.
    pub num_plays: u32,
}

/// PNG info struct
#[derive(Debug)]
pub struct Info {
    pub width: u32,
    pub height: u32,
    pub bit_depth: BitDepth,
    pub color_type: ColorType,
    pub interlaced: bool,
    pub trns: Option<Vec<u8>>,
    pub pixel_dims: Option<PixelDimensions>,
    pub palette: Option<Vec<u8>>,
    pub frame_control: Option<FrameControl>,
    pub animation_control: Option<AnimationControl>
}

impl Default for Info {
    fn default() -> Info {
        Info {
            width: 0,
            height: 0,
            bit_depth: BitDepth::Eight,
            color_type: ColorType::Grayscale,
            interlaced: false,
            palette: None,
            trns: None,
            pixel_dims: None,
            frame_control: None,
            animation_control: None
        }
    }
}

impl Info {
    /// Size of the image
    pub fn size(&self) -> (u32, u32) {
        (self.width, self.height)
    }
    
    /// Returns true if the image is an APNG image.
    pub fn is_animated(&self) -> bool {
        self.frame_control.is_some() && self.animation_control.is_some()
    }
    
    /// Returns the frame control information of the image
    pub fn animation_control(&self) -> Option<&AnimationControl> {
        self.animation_control.as_ref()
    }
    
    /// Returns the frame control information of the current frame
    pub fn frame_control(&self) -> Option<&FrameControl> {
        self.frame_control.as_ref()
    }
    
    /// Returns the bits per pixel
    pub fn bits_per_pixel(&self) -> usize {
        self.color_type.samples() * self.bit_depth as usize
    }
    
    /// Returns the bytes per pixel
    pub fn bytes_per_pixel(&self) -> usize {
        self.color_type.samples() * ((self.bit_depth as usize + 7) >> 3)
    }
    
    /// Returns the number of bytes needed for one deinterlaced image
    pub fn raw_bytes(&self) -> usize {
        self.height as usize * self.raw_row_length()
    }
    
    /// Returns the number of bytes needed for one deinterlaced row 
    pub fn raw_row_length(&self) -> usize {
        let bits = self.width as usize * self.color_type.samples() * self.bit_depth as usize;
        let extra = bits % 8;
        bits/8
        + match extra { 0 => 0, _ => 1 }
        + 1 // filter method
    }
    
    /// Returns the number of bytes needed for one deinterlaced row of width `width`
    pub fn raw_row_length_from_width(&self, width: u32) -> usize {
        let bits = width as usize * self.color_type.samples() * self.bit_depth as usize;
        let extra = bits % 8;
        bits/8
        + match extra { 0 => 0, _ => 1 }
        + 1 // filter method
    }
}


bitflags! {
    /// # Output transformations
    ///
    /// Only `IDENTITY` and `TRANSFORM_EXPAND | TRANSFORM_STRIP_ALPHA` can be used at the moment.
    pub struct Transformations: u32 {
        /// No transformation
        const IDENTITY            = 0x0000; // read and write */
        /// Strip 16-bit samples to 8 bits
        const STRIP_16            = 0x0001; // read only */
        /// Discard the alpha channel
        const STRIP_ALPHA         = 0x0002; // read only */
        /// Expand 1; 2 and 4-bit samples to bytes
        const PACKING             = 0x0004; // read and write */
        /// Change order of packed pixels to LSB first
        const PACKSWAP            = 0x0008; // read and write */
        /// Expand paletted images to RGB; expand grayscale images of
        /// less than 8-bit depth to 8-bit depth; and expand tRNS chunks
        /// to alpha channels.
        const EXPAND              = 0x0010; // read only */
        /// Invert monochrome images
        const INVERT_MONO         = 0x0020; // read and write */
        /// Normalize pixels to the sBIT depth
        const SHIFT               = 0x0040; // read and write */
        /// Flip RGB to BGR; RGBA to BGRA
        const BGR                 = 0x0080; // read and write */
        /// Flip RGBA to ARGB or GA to AG
        const SWAP_ALPHA          = 0x0100; // read and write */
        /// Byte-swap 16-bit samples
        const SWAP_ENDIAN         = 0x0200; // read and write */
        /// Change alpha from opacity to transparency
        const INVERT_ALPHA        = 0x0400; // read and write */
        const STRIP_FILLER        = 0x0800; // write only */
        const STRIP_FILLER_BEFORE = 0x0800; // write only
        const STRIP_FILLER_AFTER  = 0x1000; // write only */
        const GRAY_TO_RGB         = 0x2000; // read only */
        const EXPAND_16           = 0x4000; // read only */
        const SCALE_16            = 0x8000; // read only */
    }
}