1 //! Decoding and Encoding of PNG Images
2 //!
3 //! PNG (Portable Network Graphics) is an image format that supports lossless compression.
4 //!
5 //! # Related Links
6 //! * <http://www.w3.org/TR/PNG/> - The PNG Specification
7 //!
8
9 use std::convert::TryFrom;
10 use std::io::{self, Read, Write};
11
12 use num_rational::Ratio;
13 use png::{BlendOp, DisposeOp};
14
15 use crate::{DynamicImage, GenericImage, ImageBuffer, Luma, LumaA, RgbaImage, Rgb, Rgba};
16 use crate::animation::{Delay, Frame, Frames};
17 use crate::color::{Blend, ColorType, ExtendedColorType};
18 use crate::error::{
19 DecodingError, ImageError, ImageResult, LimitError, LimitErrorKind, ParameterError, ParameterErrorKind, UnsupportedError, UnsupportedErrorKind
20 };
21 use crate::image::{AnimationDecoder, ImageDecoder, ImageEncoder, ImageFormat};
22
23 /// Png Reader
24 ///
25 /// This reader will try to read the png one row at a time,
26 /// however for interlaced png files this is not possible and
27 /// these are therefore read at once.
28 pub struct PngReader<R: Read> {
29 reader: png::Reader<R>,
30 buffer: Vec<u8>,
31 index: usize,
32 }
33
34 /// PNG Reader
35 ///
36 /// An alias of [`PngReader`].
37 ///
38 /// TODO: remove
39 ///
40 /// [`PngReader`]: struct.PngReader.html
41 #[allow(dead_code)]
42 #[deprecated(note = "Use `PngReader` instead")]
43 pub type PNGReader<R> = PngReader<R>;
44
45 impl<R: Read> PngReader<R> {
new(mut reader: png::Reader<R>) -> ImageResult<PngReader<R>>46 fn new(mut reader: png::Reader<R>) -> ImageResult<PngReader<R>> {
47 let len = reader.output_buffer_size();
48 // Since interlaced images do not come in
49 // scanline order it is almost impossible to
50 // read them in a streaming fashion, however
51 // this shouldn't be a too big of a problem
52 // as most interlaced images should fit in memory.
53 let buffer = if reader.info().interlaced {
54 let mut buffer = vec![0; len];
55 reader.next_frame(&mut buffer).map_err(ImageError::from_png)?;
56 buffer
57 } else {
58 Vec::new()
59 };
60
61 Ok(PngReader {
62 reader,
63 buffer,
64 index: 0,
65 })
66 }
67 }
68
69 impl<R: Read> Read for PngReader<R> {
read(&mut self, mut buf: &mut [u8]) -> io::Result<usize>70 fn read(&mut self, mut buf: &mut [u8]) -> io::Result<usize> {
71 // io::Write::write for slice cannot fail
72 let readed = buf.write(&self.buffer[self.index..]).unwrap();
73
74 let mut bytes = readed;
75 self.index += readed;
76
77 while self.index >= self.buffer.len() {
78 match self.reader.next_row()? {
79 Some(row) => {
80 // Faster to copy directly to external buffer
81 let readed = buf.write(row).unwrap();
82 bytes += readed;
83
84 self.buffer = (&row[readed..]).to_owned();
85 self.index = 0;
86 }
87 None => return Ok(bytes)
88 }
89 }
90
91 Ok(bytes)
92 }
93
read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize>94 fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
95 let mut bytes = self.buffer.len();
96 if buf.is_empty() {
97 std::mem::swap(&mut self.buffer, buf);
98 } else {
99 buf.extend_from_slice(&self.buffer);
100 self.buffer.clear();
101 }
102
103 self.index = 0;
104
105 while let Some(row) = self.reader.next_row()? {
106 buf.extend_from_slice(row);
107 bytes += row.len();
108 }
109
110 Ok(bytes)
111 }
112 }
113
114 /// PNG decoder
115 pub struct PngDecoder<R: Read> {
116 color_type: ColorType,
117 reader: png::Reader<R>,
118 }
119
120 impl<R: Read> PngDecoder<R> {
121 /// Creates a new decoder that decodes from the stream ```r```
new(r: R) -> ImageResult<PngDecoder<R>>122 pub fn new(r: R) -> ImageResult<PngDecoder<R>> {
123 let limits = png::Limits {
124 bytes: usize::max_value(),
125 };
126 let mut decoder = png::Decoder::new_with_limits(r, limits);
127 // By default the PNG decoder will scale 16 bpc to 8 bpc, so custom
128 // transformations must be set. EXPAND preserves the default behavior
129 // expanding bpc < 8 to 8 bpc.
130 decoder.set_transformations(png::Transformations::EXPAND);
131 let (_, mut reader) = decoder.read_info().map_err(ImageError::from_png)?;
132 let (color_type, bits) = reader.output_color_type();
133 let color_type = match (color_type, bits) {
134 (png::ColorType::Grayscale, png::BitDepth::Eight) => ColorType::L8,
135 (png::ColorType::Grayscale, png::BitDepth::Sixteen) => ColorType::L16,
136 (png::ColorType::GrayscaleAlpha, png::BitDepth::Eight) => ColorType::La8,
137 (png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen) => ColorType::La16,
138 (png::ColorType::RGB, png::BitDepth::Eight) => ColorType::Rgb8,
139 (png::ColorType::RGB, png::BitDepth::Sixteen) => ColorType::Rgb16,
140 (png::ColorType::RGBA, png::BitDepth::Eight) => ColorType::Rgba8,
141 (png::ColorType::RGBA, png::BitDepth::Sixteen) => ColorType::Rgba16,
142
143 (png::ColorType::Grayscale, png::BitDepth::One) =>
144 return Err(unsupported_color(ExtendedColorType::L1)),
145 (png::ColorType::GrayscaleAlpha, png::BitDepth::One) =>
146 return Err(unsupported_color(ExtendedColorType::La1)),
147 (png::ColorType::RGB, png::BitDepth::One) =>
148 return Err(unsupported_color(ExtendedColorType::Rgb1)),
149 (png::ColorType::RGBA, png::BitDepth::One) =>
150 return Err(unsupported_color(ExtendedColorType::Rgba1)),
151
152 (png::ColorType::Grayscale, png::BitDepth::Two) =>
153 return Err(unsupported_color(ExtendedColorType::L2)),
154 (png::ColorType::GrayscaleAlpha, png::BitDepth::Two) =>
155 return Err(unsupported_color(ExtendedColorType::La2)),
156 (png::ColorType::RGB, png::BitDepth::Two) =>
157 return Err(unsupported_color(ExtendedColorType::Rgb2)),
158 (png::ColorType::RGBA, png::BitDepth::Two) =>
159 return Err(unsupported_color(ExtendedColorType::Rgba2)),
160
161 (png::ColorType::Grayscale, png::BitDepth::Four) =>
162 return Err(unsupported_color(ExtendedColorType::L4)),
163 (png::ColorType::GrayscaleAlpha, png::BitDepth::Four) =>
164 return Err(unsupported_color(ExtendedColorType::La4)),
165 (png::ColorType::RGB, png::BitDepth::Four) =>
166 return Err(unsupported_color(ExtendedColorType::Rgb4)),
167 (png::ColorType::RGBA, png::BitDepth::Four) =>
168 return Err(unsupported_color(ExtendedColorType::Rgba4)),
169
170 (png::ColorType::Indexed, bits) =>
171 return Err(unsupported_color(ExtendedColorType::Unknown(bits as u8))),
172 };
173
174 Ok(PngDecoder { color_type, reader })
175 }
176
177 /// Turn this into an iterator over the animation frames.
178 ///
179 /// Reading the complete animation requires more memory than reading the data from the IDAT
180 /// frame–multiple frame buffers need to be reserved at the same time. We further do not
181 /// support compositing 16-bit colors. In any case this would be lossy as the interface of
182 /// animation decoders does not support 16-bit colors.
183 ///
184 /// If something is not supported or a limit is violated then the decoding step that requires
185 /// them will fail and an error will be returned instead of the frame. No further frames will
186 /// be returned.
apng(self) -> ApngDecoder<R>187 pub fn apng(self) -> ApngDecoder<R> {
188 ApngDecoder::new(self)
189 }
190
191 /// Returns if the image contains an animation.
192 ///
193 /// Note that the file itself decides if the default image is considered to be part of the
194 /// animation. When it is not the common interpretation is to use it as a thumbnail.
195 ///
196 /// If a non-animated image is converted into an `ApngDecoder` then its iterator is empty.
is_apng(&self) -> bool197 pub fn is_apng(&self) -> bool {
198 self.reader.info().animation_control.is_some()
199 }
200 }
201
unsupported_color(ect: ExtendedColorType) -> ImageError202 fn unsupported_color(ect: ExtendedColorType) -> ImageError {
203 ImageError::Unsupported(UnsupportedError::from_format_and_kind(
204 ImageFormat::Png.into(),
205 UnsupportedErrorKind::Color(ect),
206 ))
207 }
208
209 impl<'a, R: 'a + Read> ImageDecoder<'a> for PngDecoder<R> {
210 type Reader = PngReader<R>;
211
dimensions(&self) -> (u32, u32)212 fn dimensions(&self) -> (u32, u32) {
213 self.reader.info().size()
214 }
215
color_type(&self) -> ColorType216 fn color_type(&self) -> ColorType {
217 self.color_type
218 }
219
into_reader(self) -> ImageResult<Self::Reader>220 fn into_reader(self) -> ImageResult<Self::Reader> {
221 PngReader::new(self.reader)
222 }
223
read_image(mut self, buf: &mut [u8]) -> ImageResult<()>224 fn read_image(mut self, buf: &mut [u8]) -> ImageResult<()> {
225 use byteorder::{BigEndian, ByteOrder, NativeEndian};
226
227 assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes()));
228 self.reader.next_frame(buf).map_err(ImageError::from_png)?;
229 // PNG images are big endian. For 16 bit per channel and larger types,
230 // the buffer may need to be reordered to native endianness per the
231 // contract of `read_image`.
232 // TODO: assumes equal channel bit depth.
233 let bpc = self.color_type().bytes_per_pixel() / self.color_type().channel_count();
234 match bpc {
235 1 => (), // No reodering necessary for u8
236 2 => buf.chunks_mut(2).for_each(|c| {
237 let v = BigEndian::read_u16(c);
238 NativeEndian::write_u16(c, v)
239 }),
240 _ => unreachable!(),
241 }
242 Ok(())
243 }
244
scanline_bytes(&self) -> u64245 fn scanline_bytes(&self) -> u64 {
246 let width = self.reader.info().width;
247 self.reader.output_line_size(width) as u64
248 }
249 }
250
251 /// An [`AnimationDecoder`] adapter of [`PngDecoder`].
252 ///
253 /// See [`PngDecoder::apng`] for more information.
254 ///
255 /// [`AnimationDecoder`]: ../trait.AnimationDecoder.html
256 /// [`PngDecoder`]: struct.PngDecoder.html
257 /// [`PngDecoder::apng`]: struct.PngDecoder.html#method.apng
258 pub struct ApngDecoder<R: Read> {
259 inner: PngDecoder<R>,
260 /// The current output buffer.
261 current: RgbaImage,
262 /// The previous output buffer, used for dispose op previous.
263 previous: RgbaImage,
264 /// The dispose op of the current frame.
265 dispose: DisposeOp,
266 /// The number of image still expected to be able to load.
267 remaining: u32,
268 /// The next (first) image is the thumbnail.
269 has_thumbnail: bool,
270 }
271
272 impl<R: Read> ApngDecoder<R> {
new(inner: PngDecoder<R>) -> Self273 fn new(inner: PngDecoder<R>) -> Self {
274 let (width, height) = inner.dimensions();
275 let info = inner.reader.info();
276 let remaining = match info.animation_control() {
277 // The expected number of fcTL in the remaining image.
278 Some(actl) => actl.num_frames,
279 None => 0,
280 };
281 // If the IDAT has no fcTL then it is not part of the animation counted by
282 // num_frames. All following fdAT chunks must be preceded by an fcTL
283 let has_thumbnail = info.frame_control.is_none();
284 ApngDecoder {
285 inner,
286 // TODO: should we delay this allocation? At least if we support limits we should.
287 current: RgbaImage::new(width, height),
288 previous: RgbaImage::new(width, height),
289 dispose: DisposeOp::Background,
290 remaining,
291 has_thumbnail,
292 }
293 }
294
295 // TODO: thumbnail(&mut self) -> Option<impl ImageDecoder<'_>>
296
297 /// Decode one subframe and overlay it on the canvas.
mix_next_frame(&mut self) -> Result<Option<&RgbaImage>, ImageError>298 fn mix_next_frame(&mut self) -> Result<Option<&RgbaImage>, ImageError> {
299 // Remove this image from remaining.
300 self.remaining = match self.remaining.checked_sub(1) {
301 None => return Ok(None),
302 Some(next) => next,
303 };
304
305 // Shorten ourselves to 0 in case of error.
306 let remaining = self.remaining;
307 self.remaining = 0;
308
309 // Skip the thumbnail that is not part of the animation.
310 if self.has_thumbnail {
311 self.has_thumbnail = false;
312 let mut buffer = vec![0; self.inner.reader.output_buffer_size()];
313 self.inner.reader.next_frame(&mut buffer).map_err(ImageError::from_png)?;
314 }
315
316 self.animatable_color_type()?;
317
318 // Dispose of the previous frame.
319 match self.dispose {
320 DisposeOp::None => {
321 self.previous.clone_from(&self.current);
322 }
323 DisposeOp::Background => {
324 self.previous.clone_from(&self.current);
325 self.current.pixels_mut().for_each(|pixel| *pixel = Rgba([0, 0, 0, 0]));
326 }
327 DisposeOp::Previous => {
328 self.current.clone_from(&self.previous);
329 }
330 }
331
332 // Read next frame data.
333 let mut buffer = vec![0; self.inner.reader.output_buffer_size()];
334 self.inner.reader.next_frame(&mut buffer).map_err(ImageError::from_png)?;
335 let info = self.inner.reader.info();
336
337 // Find out how to interpret the decoded frame.
338 let (width, height, px, py, blend);
339 match info.frame_control() {
340 None => {
341 width = info.width;
342 height = info.height;
343 px = 0;
344 py = 0;
345 blend = BlendOp::Source;
346 }
347 Some(fc) => {
348 width = fc.width;
349 height = fc.height;
350 px = fc.x_offset;
351 py = fc.y_offset;
352 blend = fc.blend_op;
353 self.dispose = fc.dispose_op;
354 }
355 };
356
357 // Turn the data into an rgba image proper.
358 let source = match self.inner.color_type {
359 ColorType::L8 => {
360 let image = ImageBuffer::<Luma<_>, _>::from_raw(width, height, buffer).unwrap();
361 DynamicImage::ImageLuma8(image).into_rgba8()
362 }
363 ColorType::La8 => {
364 let image = ImageBuffer::<LumaA<_>, _>::from_raw(width, height, buffer).unwrap();
365 DynamicImage::ImageLumaA8(image).into_rgba8()
366 }
367 ColorType::Rgb8 => {
368 let image = ImageBuffer::<Rgb<_>, _>::from_raw(width, height, buffer).unwrap();
369 DynamicImage::ImageRgb8(image).into_rgba8()
370 }
371 ColorType::Rgba8 => {
372 ImageBuffer::<Rgba<_>, _>::from_raw(width, height, buffer).unwrap()
373 }
374 ColorType::L16 | ColorType::Rgb16 | ColorType::La16 | ColorType::Rgba16 => {
375 // TODO: to enable remove restriction in `animatable_color_type` method.
376 unreachable!("16-bit apng not yet support")
377 }
378 _ => unreachable!("Invalid png color"),
379 };
380
381 match blend {
382 BlendOp::Source => {
383 self.current.copy_from(&source, px, py)
384 .expect("Invalid png image not detected in png");
385 }
386 BlendOp::Over => {
387 // TODO: investigate speed, speed-ups, and bounds-checks.
388 for (x, y, p) in source.enumerate_pixels() {
389 self.current.get_pixel_mut(x + px, y + py).blend(p);
390 }
391 }
392 }
393
394 // Ok, we can proceed with actually remaining images.
395 self.remaining = remaining;
396 // Return composited output buffer.
397 Ok(Some(&self.current))
398 }
399
animatable_color_type(&self) -> Result<(), ImageError>400 fn animatable_color_type(&self) -> Result<(), ImageError> {
401 match self.inner.color_type {
402 ColorType::L8 | ColorType::Rgb8 | ColorType::La8 | ColorType::Rgba8 => Ok(()),
403 // TODO: do not handle multi-byte colors. Remember to implement it in `mix_next_frame`.
404 ColorType::L16 | ColorType::Rgb16 | ColorType::La16 | ColorType::Rgba16 => {
405 Err(unsupported_color(self.inner.color_type.into()))
406 },
407 _ => unreachable!("{:?} not a valid png color", self.inner.color_type),
408 }
409 }
410 }
411
412 impl<'a, R: Read + 'a> AnimationDecoder<'a> for ApngDecoder<R> {
into_frames(self) -> Frames<'a>413 fn into_frames(self) -> Frames<'a> {
414 struct FrameIterator<R: Read>(ApngDecoder<R>);
415
416 impl<R: Read> Iterator for FrameIterator<R> {
417 type Item = ImageResult<Frame>;
418
419 fn next(&mut self) -> Option<Self::Item> {
420 let image = match self.0.mix_next_frame() {
421 Ok(Some(image)) => image.clone(),
422 Ok(None) => return None,
423 Err(err) => return Some(Err(err)),
424 };
425
426 let info = self.0.inner.reader.info();
427 let fc = info.frame_control().unwrap();
428 // PNG delays are rations in seconds.
429 let num = u32::from(fc.delay_num) * 1_000u32;
430 let denom = match fc.delay_den {
431 // The standard dictates to replace by 100 when the denominator is 0.
432 0 => 100,
433 d => u32::from(d),
434 };
435 let delay = Delay::from_ratio(Ratio::new(num, denom));
436 Some(Ok(Frame::from_parts(image, 0, 0, delay)))
437 }
438 }
439
440 Frames::new(Box::new(FrameIterator(self)))
441 }
442 }
443
444 /// PNG encoder
445 pub struct PngEncoder<W: Write> {
446 w: W,
447 compression: CompressionType,
448 filter: FilterType,
449 }
450
451 /// PNG Encoder
452 ///
453 /// An alias of [`PngEncoder`].
454 ///
455 /// TODO: remove
456 ///
457 /// [`PngEncoder`]: struct.PngEncoder.html
458 #[allow(dead_code)]
459 #[deprecated(note = "Use `PngEncoder` instead")]
460 pub type PNGEncoder<W> = PngEncoder<W>;
461
462 /// Compression level of a PNG encoder. The default setting is `Fast`.
463 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
464 pub enum CompressionType {
465 /// Default compression level
466 Default,
467 /// Fast, minimal compression
468 Fast,
469 /// High compression level
470 Best,
471 /// Huffman coding compression
472 Huffman,
473 /// Run-length encoding compression
474 Rle,
475
476 #[doc(hidden)]
477 __NonExhaustive(crate::utils::NonExhaustiveMarker),
478 }
479
480 /// Filter algorithms used to process image data to improve compression.
481 ///
482 /// The default filter is `Sub` though this default may change in the future, most notable if an
483 /// adaptive encoding option is implemented.
484 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
485 pub enum FilterType {
486 /// No processing done, best used for low bit depth greyscale or data with a
487 /// low color count
488 NoFilter,
489 /// Filters based on previous pixel in the same scanline
490 Sub,
491 /// Filters based on the scanline above
492 Up,
493 /// Filters based on the average of left and right neighbor pixels
494 Avg,
495 /// Algorithm that takes into account the left, upper left, and above pixels
496 Paeth,
497
498 #[doc(hidden)]
499 __NonExhaustive(crate::utils::NonExhaustiveMarker),
500 }
501
502 impl<W: Write> PngEncoder<W> {
503 /// Create a new encoder that writes its output to ```w```
new(w: W) -> PngEncoder<W>504 pub fn new(w: W) -> PngEncoder<W> {
505 PngEncoder {
506 w,
507 compression: CompressionType::Fast,
508 filter: FilterType::Sub,
509 }
510 }
511
512 /// Create a new encoder that writes its output to `w` with `CompressionType` `compression` and
513 /// `FilterType` `filter`.
514 ///
515 /// It is best to view the options as a _hint_ to the implementation on the smallest or fastest
516 /// option for encoding a particular image. That is, using options that map directly to a PNG
517 /// image parameter will use this parameter where possible. But variants that have no direct
518 /// mapping may be interpreted differently in minor versions. The exact output is expressly
519 /// __not__ part the SemVer stability guarantee.
520 ///
521 /// Note that it is not optimal to use a single filter type. It is likely that the library used
522 /// will at some point gain the ability to use adaptive filtering methods per pixel row (or
523 /// even interlaced row). We might make it the new default variant in which case choosing a
524 /// particular filter method likely produces larger images. Be sure to check the release notes
525 /// once in a while.
new_with_quality(w: W, compression: CompressionType, filter: FilterType) -> PngEncoder<W>526 pub fn new_with_quality(w: W, compression: CompressionType, filter: FilterType) -> PngEncoder<W> {
527 PngEncoder {
528 w,
529 compression,
530 filter,
531 }
532 }
533
534 /// Encodes the image `data` that has dimensions `width` and `height` and `ColorType` `c`.
encode(self, data: &[u8], width: u32, height: u32, color: ColorType) -> ImageResult<()>535 pub fn encode(self, data: &[u8], width: u32, height: u32, color: ColorType) -> ImageResult<()> {
536 let (ct, bits) = match color {
537 ColorType::L8 => (png::ColorType::Grayscale, png::BitDepth::Eight),
538 ColorType::L16 => (png::ColorType::Grayscale,png::BitDepth::Sixteen),
539 ColorType::La8 => (png::ColorType::GrayscaleAlpha, png::BitDepth::Eight),
540 ColorType::La16 => (png::ColorType::GrayscaleAlpha,png::BitDepth::Sixteen),
541 ColorType::Rgb8 => (png::ColorType::RGB, png::BitDepth::Eight),
542 ColorType::Rgb16 => (png::ColorType::RGB,png::BitDepth::Sixteen),
543 ColorType::Rgba8 => (png::ColorType::RGBA, png::BitDepth::Eight),
544 ColorType::Rgba16 => (png::ColorType::RGBA,png::BitDepth::Sixteen),
545 _ => return Err(ImageError::Unsupported(UnsupportedError::from_format_and_kind(
546 ImageFormat::Png.into(),
547 UnsupportedErrorKind::Color(color.into()),
548 ))),
549 };
550 let comp = match self.compression {
551 CompressionType::Default => png::Compression::Default,
552 CompressionType::Fast => png::Compression::Fast,
553 CompressionType::Best => png::Compression::Best,
554 CompressionType::Huffman => png::Compression::Huffman,
555 CompressionType::Rle => png::Compression::Rle,
556 CompressionType::__NonExhaustive(marker) => match marker._private {},
557 };
558 let filt = match self.filter {
559 FilterType::NoFilter => png::FilterType::NoFilter,
560 FilterType::Sub => png::FilterType::Sub,
561 FilterType::Up => png::FilterType::Up,
562 FilterType::Avg => png::FilterType::Avg,
563 FilterType::Paeth => png::FilterType::Paeth,
564 FilterType::__NonExhaustive(marker) => match marker._private {},
565 };
566
567 let mut encoder = png::Encoder::new(self.w, width, height);
568 encoder.set_color(ct);
569 encoder.set_depth(bits);
570 encoder.set_compression(comp);
571 encoder.set_filter(filt);
572 let mut writer = encoder.write_header().map_err(|e| ImageError::IoError(e.into()))?;
573 writer.write_image_data(data).map_err(|e| ImageError::IoError(e.into()))
574 }
575 }
576
577 impl<W: Write> ImageEncoder for PngEncoder<W> {
write_image( self, buf: &[u8], width: u32, height: u32, color_type: ColorType, ) -> ImageResult<()>578 fn write_image(
579 self,
580 buf: &[u8],
581 width: u32,
582 height: u32,
583 color_type: ColorType,
584 ) -> ImageResult<()> {
585 use byteorder::{BigEndian, ByteOrder, NativeEndian};
586
587 // PNG images are big endian. For 16 bit per channel and larger types,
588 // the buffer may need to be reordered to big endian per the
589 // contract of `write_image`.
590 // TODO: assumes equal channel bit depth.
591 let bpc = color_type.bytes_per_pixel() / color_type.channel_count();
592 match bpc {
593 1 => self.encode(buf, width, height, color_type), // No reodering necessary for u8
594 2 => {
595 // Because the buffer is immutable and the PNG encoder does not
596 // yet take Write/Read traits, create a temporary buffer for
597 // big endian reordering.
598 let mut reordered = vec![0; buf.len()];
599 buf.chunks(2)
600 .zip(reordered.chunks_mut(2))
601 .for_each(|(b, r)| BigEndian::write_u16(r, NativeEndian::read_u16(b)));
602 self.encode(&reordered, width, height, color_type)
603 },
604 _ => unreachable!(),
605 }
606 }
607 }
608
609 impl ImageError {
from_png(err: png::DecodingError) -> ImageError610 fn from_png(err: png::DecodingError) -> ImageError {
611 use png::DecodingError::*;
612 match err {
613 IoError(err) => ImageError::IoError(err),
614 err @ Format(_) => ImageError::Decoding(DecodingError::new(
615 ImageFormat::Png.into(),
616 err,
617 )),
618 LimitsExceeded => ImageError::Limits(LimitError::from_kind(
619 LimitErrorKind::InsufficientMemory,
620 )),
621 // Other is used when the buffer to `Reader::next_frame` is too small.
622 Other(message) => ImageError::Parameter(ParameterError::from_kind(
623 ParameterErrorKind::Generic(message.into_owned())
624 )),
625 err @ InvalidSignature
626 | err @ CrcMismatch { .. }
627 | err @ CorruptFlateStream => {
628 ImageError::Decoding(DecodingError::new(
629 ImageFormat::Png.into(),
630 err,
631 ))
632 }
633 }
634 }
635 }
636
637 impl Default for CompressionType {
default() -> Self638 fn default() -> Self {
639 CompressionType::Fast
640 }
641 }
642
643 impl Default for FilterType {
default() -> Self644 fn default() -> Self {
645 FilterType::Sub
646 }
647 }
648
649 #[cfg(test)]
650 mod tests {
651 use crate::image::ImageDecoder;
652 use std::io::Read;
653 use super::*;
654
655 #[test]
ensure_no_decoder_off_by_one()656 fn ensure_no_decoder_off_by_one() {
657 let dec = PngDecoder::new(std::fs::File::open("tests/images/png/bugfixes/debug_triangle_corners_widescreen.png").unwrap())
658 .expect("Unable to read PNG file (does it exist?)");
659
660 assert_eq![(2000, 1000), dec.dimensions()];
661
662 assert_eq![
663 ColorType::Rgb8,
664 dec.color_type(),
665 "Image MUST have the Rgb8 format"
666 ];
667
668 let correct_bytes = dec
669 .into_reader()
670 .expect("Unable to read file")
671 .bytes()
672 .map(|x| x.expect("Unable to read byte"))
673 .collect::<Vec<u8>>();
674
675 assert_eq![6_000_000, correct_bytes.len()];
676 }
677
678 #[test]
underlying_error()679 fn underlying_error() {
680 use std::error::Error;
681
682 let mut not_png = std::fs::read("tests/images/png/bugfixes/debug_triangle_corners_widescreen.png").unwrap();
683 not_png[0] = 0;
684
685 let error = PngDecoder::new(¬_png[..]).err().unwrap();
686 let _ = error
687 .source()
688 .unwrap()
689 .downcast_ref::<png::DecodingError>()
690 .expect("Caused by a png error");
691 }
692 }
693