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//! Decoding and Encoding of PNG Images
//!
//! PNG (Portable Network Graphics) is an image format that supports lossless compression.
//!
//! # Related Links
//! * <http://www.w3.org/TR/PNG/> - The PNG Specification
//!
use std::fmt;
use std::io::{self, Read, Write};
use png::{BlendOp, DisposeOp};
use crate::animation::{Delay, Frame, Frames, Ratio};
use crate::color::{Blend, ColorType, ExtendedColorType};
use crate::error::{
DecodingError, EncodingError, ImageError, ImageResult, LimitError, LimitErrorKind,
ParameterError, ParameterErrorKind, UnsupportedError, UnsupportedErrorKind,
};
use crate::image::{AnimationDecoder, ImageDecoder, ImageEncoder, ImageFormat};
use crate::io::Limits;
use crate::{DynamicImage, GenericImage, ImageBuffer, Luma, LumaA, Rgb, Rgba, RgbaImage};
// http://www.w3.org/TR/PNG-Structure.html
// The first eight bytes of a PNG file always contain the following (decimal) values:
pub(crate) const PNG_SIGNATURE: [u8; 8] = [137, 80, 78, 71, 13, 10, 26, 10];
/// Png Reader
///
/// This reader will try to read the png one row at a time,
/// however for interlaced png files this is not possible and
/// these are therefore read at once.
pub struct PngReader<R: Read> {
reader: png::Reader<R>,
buffer: Vec<u8>,
index: usize,
}
impl<R: Read> PngReader<R> {
fn new(mut reader: png::Reader<R>) -> ImageResult<PngReader<R>> {
let len = reader.output_buffer_size();
// Since interlaced images do not come in
// scanline order it is almost impossible to
// read them in a streaming fashion, however
// this shouldn't be a too big of a problem
// as most interlaced images should fit in memory.
let buffer = if reader.info().interlaced {
let mut buffer = vec![0; len];
reader
.next_frame(&mut buffer)
.map_err(ImageError::from_png)?;
buffer
} else {
Vec::new()
};
Ok(PngReader {
reader,
buffer,
index: 0,
})
}
}
impl<R: Read> Read for PngReader<R> {
fn read(&mut self, mut buf: &mut [u8]) -> io::Result<usize> {
// io::Write::write for slice cannot fail
let readed = buf.write(&self.buffer[self.index..]).unwrap();
let mut bytes = readed;
self.index += readed;
while self.index >= self.buffer.len() {
match self.reader.next_row()? {
Some(row) => {
// Faster to copy directly to external buffer
let readed = buf.write(row.data()).unwrap();
bytes += readed;
self.buffer = row.data()[readed..].to_owned();
self.index = 0;
}
None => return Ok(bytes),
}
}
Ok(bytes)
}
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
let mut bytes = self.buffer.len();
if buf.is_empty() {
std::mem::swap(&mut self.buffer, buf);
} else {
buf.extend_from_slice(&self.buffer);
self.buffer.clear();
}
self.index = 0;
while let Some(row) = self.reader.next_row()? {
buf.extend_from_slice(row.data());
bytes += row.data().len();
}
Ok(bytes)
}
}
/// PNG decoder
pub struct PngDecoder<R: Read> {
color_type: ColorType,
reader: png::Reader<R>,
limits: Limits,
}
impl<R: Read> PngDecoder<R> {
/// Creates a new decoder that decodes from the stream ```r```
pub fn new(r: R) -> ImageResult<PngDecoder<R>> {
Self::with_limits(r, Limits::no_limits())
}
/// Creates a new decoder that decodes from the stream ```r``` with the given limits.
pub fn with_limits(r: R, limits: Limits) -> ImageResult<PngDecoder<R>> {
limits.check_support(&crate::io::LimitSupport::default())?;
let max_bytes = usize::try_from(limits.max_alloc.unwrap_or(u64::MAX)).unwrap_or(usize::MAX);
let mut decoder = png::Decoder::new_with_limits(r, png::Limits { bytes: max_bytes });
decoder.set_ignore_text_chunk(true);
let info = decoder.read_header_info().map_err(ImageError::from_png)?;
limits.check_dimensions(info.width, info.height)?;
// By default the PNG decoder will scale 16 bpc to 8 bpc, so custom
// transformations must be set. EXPAND preserves the default behavior
// 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)))
}
};
Ok(PngDecoder {
color_type,
reader,
limits,
})
}
/// Returns the gamma value of the image or None if no gamma value is indicated.
///
/// If an sRGB chunk is present this method returns a gamma value of 0.45455 and ignores the
/// value in the gAMA chunk. This is the recommended behavior according to the PNG standard:
///
/// > When the sRGB chunk is present, [...] decoders that recognize the sRGB chunk but are not
/// > capable of colour management are recommended to ignore the gAMA and cHRM chunks, and use
/// > the values given above as if they had appeared in gAMA and cHRM chunks.
pub fn gamma_value(&self) -> ImageResult<Option<f64>> {
Ok(self
.reader
.info()
.source_gamma
.map(|x| x.into_scaled() as f64 / 100000.0))
}
/// Turn this into an iterator over the animation frames.
///
/// Reading the complete animation requires more memory than reading the data from the IDAT
/// frame–multiple frame buffers need to be reserved at the same time. We further do not
/// support compositing 16-bit colors. In any case this would be lossy as the interface of
/// animation decoders does not support 16-bit colors.
///
/// If something is not supported or a limit is violated then the decoding step that requires
/// them will fail and an error will be returned instead of the frame. No further frames will
/// be returned.
pub fn apng(self) -> ApngDecoder<R> {
ApngDecoder::new(self)
}
/// Returns if the image contains an animation.
///
/// Note that the file itself decides if the default image is considered to be part of the
/// animation. When it is not the common interpretation is to use it as a thumbnail.
///
/// If a non-animated image is converted into an `ApngDecoder` then its iterator is empty.
pub fn is_apng(&self) -> bool {
self.reader.info().animation_control.is_some()
}
}
fn unsupported_color(ect: ExtendedColorType) -> ImageError {
ImageError::Unsupported(UnsupportedError::from_format_and_kind(
ImageFormat::Png.into(),
UnsupportedErrorKind::Color(ect),
))
}
impl<'a, R: 'a + Read> ImageDecoder<'a> for PngDecoder<R> {
type Reader = PngReader<R>;
fn dimensions(&self) -> (u32, u32) {
self.reader.info().size()
}
fn color_type(&self) -> ColorType {
self.color_type
}
fn icc_profile(&mut self) -> Option<Vec<u8>> {
self.reader.info().icc_profile.as_ref().map(|x| x.to_vec())
}
fn into_reader(self) -> ImageResult<Self::Reader> {
PngReader::new(self.reader)
}
fn read_image(mut self, buf: &mut [u8]) -> ImageResult<()> {
use byteorder::{BigEndian, ByteOrder, NativeEndian};
assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes()));
self.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 to be reordered to native endianness per the
// contract of `read_image`.
// TODO: assumes equal channel bit depth.
let bpc = self.color_type().bytes_per_pixel() / self.color_type().channel_count();
match bpc {
1 => (), // No reodering necessary for u8
2 => buf.chunks_exact_mut(2).for_each(|c| {
let v = BigEndian::read_u16(c);
NativeEndian::write_u16(c, v)
}),
_ => unreachable!(),
}
Ok(())
}
fn scanline_bytes(&self) -> u64 {
let width = self.reader.info().width;
self.reader.output_line_size(width) as u64
}
fn set_limits(&mut self, limits: Limits) -> ImageResult<()> {
limits.check_support(&crate::io::LimitSupport::default())?;
let info = self.reader.info();
limits.check_dimensions(info.width, info.height)?;
self.limits = limits;
// TODO: add `png::Reader::change_limits()` and call it here
// to also constrain the internal buffer allocations in the PNG crate
Ok(())
}
}
/// An [`AnimationDecoder`] adapter of [`PngDecoder`].
///
/// See [`PngDecoder::apng`] for more information.
///
/// [`AnimationDecoder`]: ../trait.AnimationDecoder.html
/// [`PngDecoder`]: struct.PngDecoder.html
/// [`PngDecoder::apng`]: struct.PngDecoder.html#method.apng
pub struct ApngDecoder<R: Read> {
inner: PngDecoder<R>,
/// The current output buffer.
current: Option<RgbaImage>,
/// The previous output buffer, used for dispose op previous.
previous: Option<RgbaImage>,
/// The dispose op of the current frame.
dispose: DisposeOp,
/// The number of image still expected to be able to load.
remaining: u32,
/// The next (first) image is the thumbnail.
has_thumbnail: bool,
}
impl<R: Read> ApngDecoder<R> {
fn new(inner: PngDecoder<R>) -> Self {
let info = inner.reader.info();
let remaining = match info.animation_control() {
// The expected number of fcTL in the remaining image.
Some(actl) => actl.num_frames,
None => 0,
};
// If the IDAT has no fcTL then it is not part of the animation counted by
// num_frames. All following fdAT chunks must be preceded by an fcTL
let has_thumbnail = info.frame_control.is_none();
ApngDecoder {
inner,
current: None,
previous: None,
dispose: DisposeOp::Background,
remaining,
has_thumbnail,
}
}
// TODO: thumbnail(&mut self) -> Option<impl ImageDecoder<'_>>
/// Decode one subframe and overlay it on the canvas.
fn mix_next_frame(&mut self) -> Result<Option<&RgbaImage>, ImageError> {
// The iterator always produces RGBA8 images
const COLOR_TYPE: ColorType = ColorType::Rgba8;
// Allocate the buffers, honoring the memory limits
let (width, height) = self.inner.dimensions();
{
let limits = &mut self.inner.limits;
if self.previous.is_none() {
limits.reserve_buffer(width, height, COLOR_TYPE)?;
self.previous = Some(RgbaImage::new(width, height));
}
if self.current.is_none() {
limits.reserve_buffer(width, height, COLOR_TYPE)?;
self.current = Some(RgbaImage::new(width, height));
}
}
// Remove this image from remaining.
self.remaining = match self.remaining.checked_sub(1) {
None => return Ok(None),
Some(next) => next,
};
// Shorten ourselves to 0 in case of error.
let remaining = self.remaining;
self.remaining = 0;
// Skip the thumbnail that is not part of the animation.
if self.has_thumbnail {
// Clone the limits so that our one-off allocation that's destroyed after this scope doesn't persist
let mut limits = self.inner.limits.clone();
limits.reserve_usize(self.inner.reader.output_buffer_size())?;
let mut buffer = vec![0; self.inner.reader.output_buffer_size()];
// TODO: add `png::Reader::change_limits()` and call it here
// to also constrain the internal buffer allocations in the PNG crate
self.inner
.reader
.next_frame(&mut buffer)
.map_err(ImageError::from_png)?;
self.has_thumbnail = false;
}
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();
// Dispose of the previous frame.
match self.dispose {
DisposeOp::None => {
previous.clone_from(current);
}
DisposeOp::Background => {
previous.clone_from(current);
current
.pixels_mut()
.for_each(|pixel| *pixel = Rgba([0, 0, 0, 0]));
}
DisposeOp::Previous => {
current.clone_from(previous);
}
}
// The allocations from now on are not going to persist,
// and will be destroyed at the end of the scope.
// Clone the limits so that any changes to them die with the allocations.
let mut limits = self.inner.limits.clone();
// Read next frame data.
let raw_frame_size = self.inner.reader.output_buffer_size();
limits.reserve_usize(raw_frame_size)?;
let mut buffer = vec![0; raw_frame_size];
// TODO: add `png::Reader::change_limits()` and call it here
// to also constrain the internal buffer allocations in the PNG crate
self.inner
.reader
.next_frame(&mut buffer)
.map_err(ImageError::from_png)?;
let info = self.inner.reader.info();
// Find out how to interpret the decoded frame.
let (width, height, px, py, blend);
match info.frame_control() {
None => {
width = info.width;
height = info.height;
px = 0;
py = 0;
blend = BlendOp::Source;
}
Some(fc) => {
width = fc.width;
height = fc.height;
px = fc.x_offset;
py = fc.y_offset;
blend = fc.blend_op;
self.dispose = fc.dispose_op;
}
};
// Turn the data into an rgba image proper.
limits.reserve_buffer(width, height, COLOR_TYPE)?;
let source = match self.inner.color_type {
ColorType::L8 => {
let image = ImageBuffer::<Luma<_>, _>::from_raw(width, height, buffer).unwrap();
DynamicImage::ImageLuma8(image).into_rgba8()
}
ColorType::La8 => {
let image = ImageBuffer::<LumaA<_>, _>::from_raw(width, height, buffer).unwrap();
DynamicImage::ImageLumaA8(image).into_rgba8()
}
ColorType::Rgb8 => {
let image = ImageBuffer::<Rgb<_>, _>::from_raw(width, height, buffer).unwrap();
DynamicImage::ImageRgb8(image).into_rgba8()
}
ColorType::Rgba8 => ImageBuffer::<Rgba<_>, _>::from_raw(width, height, buffer).unwrap(),
ColorType::L16 | ColorType::Rgb16 | ColorType::La16 | ColorType::Rgba16 => {
// TODO: to enable remove restriction in `animatable_color_type` method.
unreachable!("16-bit apng not yet support")
}
_ => unreachable!("Invalid png color"),
};
// We've converted the raw frame to RGBA8 and disposed of the original allocation
limits.free_usize(raw_frame_size);
match blend {
BlendOp::Source => {
current
.copy_from(&source, px, py)
.expect("Invalid png image not detected in png");
}
BlendOp::Over => {
// TODO: investigate speed, speed-ups, and bounds-checks.
for (x, y, p) in source.enumerate_pixels() {
current.get_pixel_mut(x + px, y + py).blend(p);
}
}
}
// Ok, we can proceed with actually remaining images.
self.remaining = remaining;
// Return composited output buffer.
Ok(Some(self.current.as_ref().unwrap()))
}
fn animatable_color_type(&self) -> Result<(), ImageError> {
match self.inner.color_type {
ColorType::L8 | ColorType::Rgb8 | ColorType::La8 | ColorType::Rgba8 => Ok(()),
// TODO: do not handle multi-byte colors. Remember to implement it in `mix_next_frame`.
ColorType::L16 | ColorType::Rgb16 | ColorType::La16 | ColorType::Rgba16 => {
Err(unsupported_color(self.inner.color_type.into()))
}
_ => unreachable!("{:?} not a valid png color", self.inner.color_type),
}
}
}
impl<'a, R: Read + 'a> AnimationDecoder<'a> for ApngDecoder<R> {
fn into_frames(self) -> Frames<'a> {
struct FrameIterator<R: Read>(ApngDecoder<R>);
impl<R: Read> Iterator for FrameIterator<R> {
type Item = ImageResult<Frame>;
fn next(&mut self) -> Option<Self::Item> {
let image = match self.0.mix_next_frame() {
Ok(Some(image)) => image.clone(),
Ok(None) => return None,
Err(err) => return Some(Err(err)),
};
let info = self.0.inner.reader.info();
let fc = info.frame_control().unwrap();
// PNG delays are rations in seconds.
let num = u32::from(fc.delay_num) * 1_000u32;
let denom = match fc.delay_den {
// The standard dictates to replace by 100 when the denominator is 0.
0 => 100,
d => u32::from(d),
};
let delay = Delay::from_ratio(Ratio::new(num, denom));
Some(Ok(Frame::from_parts(image, 0, 0, delay)))
}
}
Frames::new(Box::new(FrameIterator(self)))
}
}
/// PNG encoder
pub struct PngEncoder<W: Write> {
w: W,
compression: CompressionType,
filter: FilterType,
}
/// Compression level of a PNG encoder. The default setting is `Fast`.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[non_exhaustive]
#[derive(Default)]
pub enum CompressionType {
/// Default compression level
Default,
/// Fast, minimal compression
#[default]
Fast,
/// High compression level
Best,
/// Huffman coding compression
#[deprecated(note = "use one of the other compression levels instead, such as 'Fast'")]
Huffman,
/// Run-length encoding compression
#[deprecated(note = "use one of the other compression levels instead, such as 'Fast'")]
Rle,
}
/// Filter algorithms used to process image data to improve compression.
///
/// The default filter is `Adaptive`.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[non_exhaustive]
#[derive(Default)]
pub enum FilterType {
/// No processing done, best used for low bit depth grayscale or data with a
/// low color count
NoFilter,
/// Filters based on previous pixel in the same scanline
Sub,
/// Filters based on the scanline above
Up,
/// Filters based on the average of left and right neighbor pixels
Avg,
/// Algorithm that takes into account the left, upper left, and above pixels
Paeth,
/// Uses a heuristic to select one of the preceding filters for each
/// scanline rather than one filter for the entire image
#[default]
Adaptive,
}
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[non_exhaustive]
enum BadPngRepresentation {
ColorType(ColorType),
}
impl<W: Write> PngEncoder<W> {
/// Create a new encoder that writes its output to ```w```
pub fn new(w: W) -> PngEncoder<W> {
PngEncoder {
w,
compression: CompressionType::default(),
filter: FilterType::default(),
}
}
/// Create a new encoder that writes its output to `w` with `CompressionType` `compression` and
/// `FilterType` `filter`.
///
/// It is best to view the options as a _hint_ to the implementation on the smallest or fastest
/// option for encoding a particular image. That is, using options that map directly to a PNG
/// image parameter will use this parameter where possible. But variants that have no direct
/// mapping may be interpreted differently in minor versions. The exact output is expressly
/// __not__ part of the SemVer stability guarantee.
///
/// Note that it is not optimal to use a single filter type, so an adaptive
/// filter type is selected as the default. The filter which best minimizes
/// file size may change with the type of compression used.
pub fn new_with_quality(
w: W,
compression: CompressionType,
filter: FilterType,
) -> PngEncoder<W> {
PngEncoder {
w,
compression,
filter,
}
}
/// Encodes the image `data` that has dimensions `width` and `height` and `ColorType` `c`.
///
/// Expects data in big endian.
#[deprecated = "Use `PngEncoder::write_image` instead. Beware that `write_image` has a different endianness convention"]
pub fn encode(self, data: &[u8], width: u32, height: u32, color: ColorType) -> ImageResult<()> {
self.encode_inner(data, width, height, color)
}
fn encode_inner(
self,
data: &[u8],
width: u32,
height: u32,
color: ColorType,
) -> ImageResult<()> {
let (ct, bits) = match color {
ColorType::L8 => (png::ColorType::Grayscale, png::BitDepth::Eight),
ColorType::L16 => (png::ColorType::Grayscale, png::BitDepth::Sixteen),
ColorType::La8 => (png::ColorType::GrayscaleAlpha, png::BitDepth::Eight),
ColorType::La16 => (png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen),
ColorType::Rgb8 => (png::ColorType::Rgb, png::BitDepth::Eight),
ColorType::Rgb16 => (png::ColorType::Rgb, png::BitDepth::Sixteen),
ColorType::Rgba8 => (png::ColorType::Rgba, png::BitDepth::Eight),
ColorType::Rgba16 => (png::ColorType::Rgba, png::BitDepth::Sixteen),
_ => {
return Err(ImageError::Unsupported(
UnsupportedError::from_format_and_kind(
ImageFormat::Png.into(),
UnsupportedErrorKind::Color(color.into()),
),
))
}
};
let comp = match self.compression {
CompressionType::Default => png::Compression::Default,
CompressionType::Best => png::Compression::Best,
_ => png::Compression::Fast,
};
let (filter, adaptive_filter) = match self.filter {
FilterType::NoFilter => (
png::FilterType::NoFilter,
png::AdaptiveFilterType::NonAdaptive,
),
FilterType::Sub => (png::FilterType::Sub, png::AdaptiveFilterType::NonAdaptive),
FilterType::Up => (png::FilterType::Up, png::AdaptiveFilterType::NonAdaptive),
FilterType::Avg => (png::FilterType::Avg, png::AdaptiveFilterType::NonAdaptive),
FilterType::Paeth => (png::FilterType::Paeth, png::AdaptiveFilterType::NonAdaptive),
FilterType::Adaptive => (png::FilterType::Sub, png::AdaptiveFilterType::Adaptive),
};
let mut encoder = png::Encoder::new(self.w, width, height);
encoder.set_color(ct);
encoder.set_depth(bits);
encoder.set_compression(comp);
encoder.set_filter(filter);
encoder.set_adaptive_filter(adaptive_filter);
let mut writer = encoder
.write_header()
.map_err(|e| ImageError::IoError(e.into()))?;
writer
.write_image_data(data)
.map_err(|e| ImageError::IoError(e.into()))
}
}
impl<W: Write> ImageEncoder for PngEncoder<W> {
/// Write a PNG image with the specified width, height, and color type.
///
/// For color types with 16-bit per channel or larger, the contents of `buf` should be in
/// native endian. PngEncoder will automatically convert to big endian as required by the
/// underlying PNG format.
#[track_caller]
fn write_image(
self,
buf: &[u8],
width: u32,
height: u32,
color_type: ColorType,
) -> ImageResult<()> {
use byteorder::{BigEndian, ByteOrder, NativeEndian};
use ColorType::*;
let expected_bufffer_len =
(width as u64 * height as u64).saturating_mul(color_type.bytes_per_pixel() as u64);
assert_eq!(
expected_bufffer_len,
buf.len() as u64,
"Invalid buffer length: expected {expected_bufffer_len} got {} for {width}x{height} image",
buf.len(),
);
// PNG images are big endian. For 16 bit per channel and larger types,
// the buffer may need to be reordered to big endian per the
// contract of `write_image`.
// TODO: assumes equal channel bit depth.
match color_type {
L8 | La8 | Rgb8 | Rgba8 => {
// No reodering necessary for u8
self.encode_inner(buf, width, height, color_type)
}
L16 | La16 | Rgb16 | Rgba16 => {
// Because the buffer is immutable and the PNG encoder does not
// yet take Write/Read traits, create a temporary buffer for
// big endian reordering.
let mut reordered = vec![0; buf.len()];
buf.chunks_exact(2)
.zip(reordered.chunks_exact_mut(2))
.for_each(|(b, r)| BigEndian::write_u16(r, NativeEndian::read_u16(b)));
self.encode_inner(&reordered, width, height, color_type)
}
_ => Err(ImageError::Encoding(EncodingError::new(
ImageFormat::Png.into(),
BadPngRepresentation::ColorType(color_type),
))),
}
}
}
impl ImageError {
fn from_png(err: png::DecodingError) -> ImageError {
use png::DecodingError::*;
match err {
IoError(err) => ImageError::IoError(err),
// The input image was not a valid PNG.
err @ Format(_) => {
ImageError::Decoding(DecodingError::new(ImageFormat::Png.into(), err))
}
// Other is used when:
// - The decoder is polled for more animation frames despite being done (or not being animated
// in the first place).
// - The output buffer does not have the required size.
err @ Parameter(_) => ImageError::Parameter(ParameterError::from_kind(
ParameterErrorKind::Generic(err.to_string()),
)),
LimitsExceeded => {
ImageError::Limits(LimitError::from_kind(LimitErrorKind::InsufficientMemory))
}
}
}
}
impl fmt::Display for BadPngRepresentation {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Self::ColorType(color_type) => write!(
f,
"The color {:?} can not be represented in PNG.",
color_type
),
}
}
}
impl std::error::Error for BadPngRepresentation {}
#[cfg(test)]
mod tests {
use super::*;
use crate::ImageOutputFormat;
use std::io::Cursor;
#[test]
fn ensure_no_decoder_off_by_one() {
let dec = PngDecoder::new(
std::fs::File::open("tests/images/png/bugfixes/debug_triangle_corners_widescreen.png")
.unwrap(),
)
.expect("Unable to read PNG file (does it exist?)");
assert_eq![(2000, 1000), dec.dimensions()];
assert_eq![
ColorType::Rgb8,
dec.color_type(),
"Image MUST have the Rgb8 format"
];
#[allow(deprecated)]
let correct_bytes = dec
.into_reader()
.expect("Unable to read file")
.bytes()
.map(|x| x.expect("Unable to read byte"))
.collect::<Vec<u8>>();
assert_eq![6_000_000, correct_bytes.len()];
}
#[test]
fn underlying_error() {
use std::error::Error;
let mut not_png =
std::fs::read("tests/images/png/bugfixes/debug_triangle_corners_widescreen.png")
.unwrap();
not_png[0] = 0;
let error = PngDecoder::new(¬_png[..]).err().unwrap();
let _ = error
.source()
.unwrap()
.downcast_ref::<png::DecodingError>()
.expect("Caused by a png error");
}
#[test]
fn encode_bad_color_type() {
// regression test for issue #1663
let image = DynamicImage::new_rgb32f(1, 1);
let mut target = Cursor::new(vec![]);
let _ = image.write_to(&mut target, ImageOutputFormat::Png);
}
}