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PNG: Simplified color parsing logic #3051

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162 changes: 56 additions & 106 deletions src/codecs/png.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,63 +85,9 @@ impl<R: BufRead + Seek> PngDecoder<R> {
// expanding bpc < 8 to 8 bpc.
decoder.set_transformations(png::Transformations::EXPAND);
let reader = decoder.read_info().map_err(ImageError::from_png)?;
let (color_type, bits) = reader.output_color_type();

let color_type = match (color_type, bits) {
(png::ColorType::Grayscale, png::BitDepth::Eight) => ColorType::L8,
(png::ColorType::Grayscale, png::BitDepth::Sixteen) => ColorType::L16,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Eight) => ColorType::La8,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen) => ColorType::La16,
(png::ColorType::Rgb, png::BitDepth::Eight) => ColorType::Rgb8,
(png::ColorType::Rgb, png::BitDepth::Sixteen) => ColorType::Rgb16,
(png::ColorType::Rgba, png::BitDepth::Eight) => ColorType::Rgba8,
(png::ColorType::Rgba, png::BitDepth::Sixteen) => ColorType::Rgba16,

(png::ColorType::Grayscale, png::BitDepth::One) => {
return Err(unsupported_color(ExtendedColorType::L1))
}
(png::ColorType::GrayscaleAlpha, png::BitDepth::One) => {
return Err(unsupported_color(ExtendedColorType::La1))
}
(png::ColorType::Rgb, png::BitDepth::One) => {
return Err(unsupported_color(ExtendedColorType::Rgb1))
}
(png::ColorType::Rgba, png::BitDepth::One) => {
return Err(unsupported_color(ExtendedColorType::Rgba1))
}

(png::ColorType::Grayscale, png::BitDepth::Two) => {
return Err(unsupported_color(ExtendedColorType::L2))
}
(png::ColorType::GrayscaleAlpha, png::BitDepth::Two) => {
return Err(unsupported_color(ExtendedColorType::La2))
}
(png::ColorType::Rgb, png::BitDepth::Two) => {
return Err(unsupported_color(ExtendedColorType::Rgb2))
}
(png::ColorType::Rgba, png::BitDepth::Two) => {
return Err(unsupported_color(ExtendedColorType::Rgba2))
}

(png::ColorType::Grayscale, png::BitDepth::Four) => {
return Err(unsupported_color(ExtendedColorType::L4))
}
(png::ColorType::GrayscaleAlpha, png::BitDepth::Four) => {
return Err(unsupported_color(ExtendedColorType::La4))
}
(png::ColorType::Rgb, png::BitDepth::Four) => {
return Err(unsupported_color(ExtendedColorType::Rgb4))
}
(png::ColorType::Rgba, png::BitDepth::Four) => {
return Err(unsupported_color(ExtendedColorType::Rgba4))
}

(png::ColorType::Indexed, bits) => {
return Err(unsupported_color(ExtendedColorType::Unknown(bits as u8)))
}
};
let (color_type, bit_depth) = reader.output_color_type();
self.color_type = to_supported_color_type(color_type, bit_depth)?;

self.color_type = color_type;
Ok(self.reader.insert(reader))
}

Expand Down Expand Up @@ -186,36 +132,6 @@ impl<R: BufRead + Seek> PngDecoder<R> {
Ok(reader.info().animation_control.is_some())
}

fn color_type_info(info: &png::Info<'_>) -> ExtendedColorType {
match (info.color_type, info.bit_depth) {
(png::ColorType::Grayscale, png::BitDepth::One) => ExtendedColorType::L1,
(png::ColorType::Grayscale, png::BitDepth::Two) => ExtendedColorType::L2,
(png::ColorType::Grayscale, png::BitDepth::Four) => ExtendedColorType::L4,
(png::ColorType::Grayscale, png::BitDepth::Eight) => ExtendedColorType::L8,
(png::ColorType::Grayscale, png::BitDepth::Sixteen) => ExtendedColorType::L16,
(png::ColorType::GrayscaleAlpha, png::BitDepth::One) => ExtendedColorType::La1,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Two) => ExtendedColorType::La2,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Four) => ExtendedColorType::La4,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Eight) => ExtendedColorType::La8,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen) => ExtendedColorType::La16,
(png::ColorType::Rgb, png::BitDepth::One) => ExtendedColorType::Rgb1,
(png::ColorType::Rgb, png::BitDepth::Two) => ExtendedColorType::Rgb2,
(png::ColorType::Rgb, png::BitDepth::Four) => ExtendedColorType::Rgb4,
(png::ColorType::Rgb, png::BitDepth::Eight) => ExtendedColorType::Rgb8,
(png::ColorType::Rgb, png::BitDepth::Sixteen) => ExtendedColorType::Rgb16,
(png::ColorType::Rgba, png::BitDepth::One) => ExtendedColorType::Rgba1,
(png::ColorType::Rgba, png::BitDepth::Two) => ExtendedColorType::Rgba2,
(png::ColorType::Rgba, png::BitDepth::Four) => ExtendedColorType::Rgba4,
(png::ColorType::Rgba, png::BitDepth::Eight) => ExtendedColorType::Rgba8,
(png::ColorType::Rgba, png::BitDepth::Sixteen) => ExtendedColorType::Rgba16,
(png::ColorType::Indexed, png::BitDepth::One) => ExtendedColorType::Unknown(1),
(png::ColorType::Indexed, png::BitDepth::Two) => ExtendedColorType::Unknown(2),
(png::ColorType::Indexed, png::BitDepth::Four) => ExtendedColorType::Unknown(4),
(png::ColorType::Indexed, png::BitDepth::Eight) => ExtendedColorType::Unknown(8),
(png::ColorType::Indexed, png::BitDepth::Sixteen) => ExtendedColorType::Unknown(16),
}
}

/// The maximum number of bytes iTXt and zTXt are allowed to decompress to.
/// This guards against decompression bombs.
fn text_decompress_limit(&mut self) -> usize {
Expand All @@ -224,6 +140,58 @@ impl<R: BufRead + Seek> PngDecoder<R> {
}
}

fn to_supported_color_type(
color_type: png::ColorType,
bit_depth: png::BitDepth,
) -> ImageResult<ColorType> {
match (color_type, bit_depth) {
(png::ColorType::Grayscale, png::BitDepth::Eight) => Ok(ColorType::L8),
(png::ColorType::Grayscale, png::BitDepth::Sixteen) => Ok(ColorType::L16),
(png::ColorType::GrayscaleAlpha, png::BitDepth::Eight) => Ok(ColorType::La8),
(png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen) => Ok(ColorType::La16),
(png::ColorType::Rgb, png::BitDepth::Eight) => Ok(ColorType::Rgb8),
(png::ColorType::Rgb, png::BitDepth::Sixteen) => Ok(ColorType::Rgb16),
(png::ColorType::Rgba, png::BitDepth::Eight) => Ok(ColorType::Rgba8),
(png::ColorType::Rgba, png::BitDepth::Sixteen) => Ok(ColorType::Rgba16),

_ => Err(unsupported_color(to_extended_color_type(
color_type, bit_depth,
))),
}
}
fn to_extended_color_type(
color_type: png::ColorType,
bit_depth: png::BitDepth,
) -> ExtendedColorType {
match (color_type, bit_depth) {
(png::ColorType::Grayscale, png::BitDepth::One) => ExtendedColorType::L1,
(png::ColorType::Grayscale, png::BitDepth::Two) => ExtendedColorType::L2,
(png::ColorType::Grayscale, png::BitDepth::Four) => ExtendedColorType::L4,
(png::ColorType::Grayscale, png::BitDepth::Eight) => ExtendedColorType::L8,
(png::ColorType::Grayscale, png::BitDepth::Sixteen) => ExtendedColorType::L16,
(png::ColorType::GrayscaleAlpha, png::BitDepth::One) => ExtendedColorType::La1,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Two) => ExtendedColorType::La2,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Four) => ExtendedColorType::La4,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Eight) => ExtendedColorType::La8,
(png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen) => ExtendedColorType::La16,
(png::ColorType::Rgb, png::BitDepth::One) => ExtendedColorType::Rgb1,
(png::ColorType::Rgb, png::BitDepth::Two) => ExtendedColorType::Rgb2,
(png::ColorType::Rgb, png::BitDepth::Four) => ExtendedColorType::Rgb4,
(png::ColorType::Rgb, png::BitDepth::Eight) => ExtendedColorType::Rgb8,
(png::ColorType::Rgb, png::BitDepth::Sixteen) => ExtendedColorType::Rgb16,
(png::ColorType::Rgba, png::BitDepth::One) => ExtendedColorType::Rgba1,
(png::ColorType::Rgba, png::BitDepth::Two) => ExtendedColorType::Rgba2,
(png::ColorType::Rgba, png::BitDepth::Four) => ExtendedColorType::Rgba4,
(png::ColorType::Rgba, png::BitDepth::Eight) => ExtendedColorType::Rgba8,
(png::ColorType::Rgba, png::BitDepth::Sixteen) => ExtendedColorType::Rgba16,
(png::ColorType::Indexed, png::BitDepth::One) => ExtendedColorType::Unknown(1),
(png::ColorType::Indexed, png::BitDepth::Two) => ExtendedColorType::Unknown(2),
(png::ColorType::Indexed, png::BitDepth::Four) => ExtendedColorType::Unknown(4),
(png::ColorType::Indexed, png::BitDepth::Eight) => ExtendedColorType::Unknown(8),
(png::ColorType::Indexed, png::BitDepth::Sixteen) => ExtendedColorType::Unknown(16),
}
}

fn attributes_from_info(info: &png::Info<'_>) -> DecodedImageAttributes {
let delay = info.frame_control().map(|fc| {
// PNG delays are rations in seconds.
Expand Down Expand Up @@ -358,7 +326,8 @@ impl<R: BufRead + Seek> ImageDecoder for PngDecoder<R> {
assert_eq!(u64::try_from(buf.len()), Ok(layout.total_bytes()));

let reader = self.ensure_reader_and_header()?;
let original_color_type = Self::color_type_info(reader.info());
let info = reader.info();
let original_color_type = to_extended_color_type(info.color_type, info.bit_depth);
reader.next_frame(buf).map_err(ImageError::from_png)?;

// PNG images are big endian. For 16 bit per channel and larger types, the buffer may need
Expand Down Expand Up @@ -492,8 +461,6 @@ impl<R: BufRead + Seek> ApngDecoder<R> {
}
}

self.animatable_color_type()?;

// We've initialized them earlier in this function
let previous = self.previous.as_mut().unwrap();
let current = self.current.as_mut().unwrap();
Expand Down Expand Up @@ -617,23 +584,6 @@ impl<R: BufRead + Seek> ApngDecoder<R> {

Ok(Some(attributes))
}

fn animatable_color_type(&self) -> Result<(), ImageError> {
match self.inner.color_type {
ColorType::L8
| ColorType::Rgb8
| ColorType::La8
| ColorType::Rgba8
| ColorType::L16
| ColorType::Rgb16
| ColorType::La16
| ColorType::Rgba16 => Ok(()),
_ => {
debug_assert!(false, "{:?} not a valid png color", self.inner.color_type);
Err(unsupported_color(self.inner.color_type.into()))
}
}
}
}

impl<R: BufRead + Seek> ImageDecoder for ApngDecoder<R> {
Expand Down
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