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Decode-only Info (part 1/x) #551

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merged 5 commits into from
Dec 20, 2024
Merged

Decode-only Info (part 1/x) #551

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7892e3b
Parallelize roundtrip tests
kornelski Dec 18, 2024
be425a3
Move Info::encode
kornelski Dec 18, 2024
57f3ab1
Separate PartialInfo from Info
kornelski Dec 18, 2024
6d5d64f
Compression belongs to Options
kornelski Dec 18, 2024
ff6372d
Don't use source_ fields for output
kornelski Dec 18, 2024
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123 changes: 31 additions & 92 deletions src/common.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
//! Common types shared between the encoder and decoder
use crate::text_metadata::{EncodableTextChunk, ITXtChunk, TEXtChunk, ZTXtChunk};
use crate::text_metadata::{ITXtChunk, TEXtChunk, ZTXtChunk};
use crate::{chunk, encoder};
use io::Write;
use std::{borrow::Cow, convert::TryFrom, fmt, io};
Expand Down Expand Up @@ -77,6 +77,16 @@ impl ColorType {
|| self == ColorType::Rgba))
|| (bit_depth == BitDepth::Sixteen && self == ColorType::Indexed)
}

pub(crate) fn bits_per_pixel(&self, bit_depth: BitDepth) -> usize {
self.samples() * bit_depth as usize
}

pub(crate) fn bytes_per_pixel(&self, bit_depth: BitDepth) -> usize {
// If adjusting this for expansion or other transformation passes, remember to keep the old
// implementation for bpp_in_prediction, which is internal to the png specification.
self.samples() * ((bit_depth as usize + 7) >> 3)
}
}

/// Bit depth of the PNG file.
Expand Down Expand Up @@ -587,7 +597,6 @@ pub struct Info<'a> {

pub frame_control: Option<FrameControl>,
pub animation_control: Option<AnimationControl>,
pub compression: Compression,
/// Gamma of the source system.
/// Set by both `gAMA` as well as to a replacement by `sRGB` chunk.
pub source_gamma: Option<ScaledFloat>,
Expand Down Expand Up @@ -633,9 +642,6 @@ impl Default for Info<'_> {
pixel_dims: None,
frame_control: None,
animation_control: None,
// Default to `deflate::Compression::Fast` and `filter::FilterType::Sub`
// to maintain backward compatible output.
compression: Compression::Fast,
source_gamma: None,
source_chromaticities: None,
srgb: None,
Expand Down Expand Up @@ -683,14 +689,14 @@ impl Info<'_> {

/// Returns the number of bits per pixel.
pub fn bits_per_pixel(&self) -> usize {
self.color_type.samples() * self.bit_depth as usize
self.color_type.bits_per_pixel(self.bit_depth)
}

/// Returns the number of bytes per pixel.
pub fn bytes_per_pixel(&self) -> usize {
// If adjusting this for expansion or other transformation passes, remember to keep the old
// implementation for bpp_in_prediction, which is internal to the png specification.
self.color_type.samples() * ((self.bit_depth as usize + 7) >> 3)
self.color_type.bytes_per_pixel(self.bit_depth)
}

/// Return the number of bytes for this pixel used in prediction.
Expand Down Expand Up @@ -725,6 +731,24 @@ impl Info<'_> {
.raw_row_length_from_width(self.bit_depth, width)
}

/// Gamma dependent on sRGB chunk
pub fn gamma(&self) -> Option<ScaledFloat> {
if self.srgb.is_some() {
Some(crate::srgb::substitute_gamma())
} else {
self.gama_chunk
}
}

/// Chromaticities dependent on sRGB chunk
pub fn chromaticities(&self) -> Option<SourceChromaticities> {
if self.srgb.is_some() {
Some(crate::srgb::substitute_chromaticities())
} else {
self.chrm_chunk
}
}

/// Mark the image data as conforming to the SRGB color space with the specified rendering intent.
///
/// Any ICC profiles will be ignored.
Expand All @@ -735,91 +759,6 @@ impl Info<'_> {
self.srgb = Some(rendering_intent);
self.icc_profile = None;
}

/// Encode this header to the writer.
///
/// Note that this does _not_ include the PNG signature, it starts with the IHDR chunk and then
/// includes other chunks that were added to the header.
#[deprecated(note = "Use Encoder+Writer instead")]
pub fn encode<W: Write>(&self, mut w: W) -> encoder::Result<()> {
// Encode the IHDR chunk
let mut data = [0; 13];
data[..4].copy_from_slice(&self.width.to_be_bytes());
data[4..8].copy_from_slice(&self.height.to_be_bytes());
data[8] = self.bit_depth as u8;
data[9] = self.color_type as u8;
data[12] = self.interlaced as u8;
encoder::write_chunk(&mut w, chunk::IHDR, &data)?;

// Encode the pHYs chunk
if let Some(pd) = self.pixel_dims {
let mut phys_data = [0; 9];
phys_data[0..4].copy_from_slice(&pd.xppu.to_be_bytes());
phys_data[4..8].copy_from_slice(&pd.yppu.to_be_bytes());
match pd.unit {
Unit::Meter => phys_data[8] = 1,
Unit::Unspecified => phys_data[8] = 0,
}
encoder::write_chunk(&mut w, chunk::pHYs, &phys_data)?;
}

// If specified, the sRGB information overrides the source gamma and chromaticities.
if let Some(srgb) = &self.srgb {
srgb.encode(&mut w)?;

// gAMA and cHRM are optional, for backwards compatibility
let srgb_gamma = crate::srgb::substitute_gamma();
if Some(srgb_gamma) == self.source_gamma {
srgb_gamma.encode_gama(&mut w)?
}
let srgb_chromaticities = crate::srgb::substitute_chromaticities();
if Some(srgb_chromaticities) == self.source_chromaticities {
srgb_chromaticities.encode(&mut w)?;
}
} else {
if let Some(gma) = self.source_gamma {
gma.encode_gama(&mut w)?
}
if let Some(chrms) = self.source_chromaticities {
chrms.encode(&mut w)?;
}
if let Some(iccp) = &self.icc_profile {
encoder::write_iccp_chunk(&mut w, "_", iccp)?
}
}

if let Some(exif) = &self.exif_metadata {
encoder::write_chunk(&mut w, chunk::eXIf, exif)?;
}

if let Some(actl) = self.animation_control {
actl.encode(&mut w)?;
}

// The position of the PLTE chunk is important, it must come before the tRNS chunk and after
// many of the other metadata chunks.
if let Some(p) = &self.palette {
encoder::write_chunk(&mut w, chunk::PLTE, p)?;
};

if let Some(t) = &self.trns {
encoder::write_chunk(&mut w, chunk::tRNS, t)?;
}

for text_chunk in &self.uncompressed_latin1_text {
text_chunk.encode(&mut w)?;
}

for text_chunk in &self.compressed_latin1_text {
text_chunk.encode(&mut w)?;
}

for text_chunk in &self.utf8_text {
text_chunk.encode(&mut w)?;
}

Ok(())
}
}

impl BytesPerPixel {
Expand Down
16 changes: 2 additions & 14 deletions src/decoder/stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1315,11 +1315,6 @@ impl StreamingDecoder {
};

info.chrm_chunk = Some(source_chromaticities);
// Ignore chromaticities if sRGB profile is used.
if info.srgb.is_none() {
info.source_chromaticities = Some(source_chromaticities);
}

Ok(Decoded::Nothing)
}
}
Expand All @@ -1340,11 +1335,6 @@ impl StreamingDecoder {
let source_gamma = ScaledFloat::from_scaled(source_gamma);

info.gama_chunk = Some(source_gamma);
// Ignore chromaticities if sRGB profile is used.
if info.srgb.is_none() {
info.source_gamma = Some(source_gamma);
}

Ok(Decoded::Nothing)
}
}
Expand All @@ -1368,8 +1358,6 @@ impl StreamingDecoder {

// Set srgb and override source gamma and chromaticities.
info.srgb = Some(rendering_intent);
info.source_gamma = Some(crate::srgb::substitute_gamma());
info.source_chromaticities = Some(crate::srgb::substitute_chromaticities());
Ok(Decoded::Nothing)
}
}
Expand Down Expand Up @@ -1846,7 +1834,7 @@ mod tests {
fn trial(path: &str, expected: Option<ScaledFloat>) {
let decoder = crate::Decoder::new(File::open(path).unwrap());
let reader = decoder.read_info().unwrap();
let actual: Option<ScaledFloat> = reader.info().source_gamma;
let actual: Option<ScaledFloat> = reader.info().gamma();
assert!(actual == expected);
}
trial("tests/pngsuite/f00n0g08.png", None);
Expand Down Expand Up @@ -1887,7 +1875,7 @@ mod tests {
fn trial(path: &str, expected: Option<SourceChromaticities>) {
let decoder = crate::Decoder::new(File::open(path).unwrap());
let reader = decoder.read_info().unwrap();
let actual: Option<SourceChromaticities> = reader.info().source_chromaticities;
let actual: Option<SourceChromaticities> = reader.info().chromaticities();
assert!(actual == expected);
}
trial(
Expand Down
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