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LibGfx/TIFF: Skip channels that we are unable to interpret

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As per the specification, TIFF readers should gracefully skip samples
that they are not able to interpret.

This patch allow us to read `strike.tif` from the libtiff test suite as
an RGB image.
This commit is contained in:
Lucas CHOLLET 2023-12-16 20:25:49 -05:00 • committed by Andreas Kling
parent a443d2955a
commit caf9f00456
1 changed files with 26 additions and 0 deletions
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26
Userland/Libraries/LibGfx/ImageFormats/TIFFLoader.cpp
View file

@ -87,13 +87,38 @@ private:
return NumericLimits<u8>::max() * value / ((1 << bits) - 1);
}
u8 samples_for_photometric_interpretation() const
{
switch (*m_metadata.photometric_interpretation()) {
case PhotometricInterpretation::WhiteIsZero:
case PhotometricInterpretation::BlackIsZero:
return 1;
case PhotometricInterpretation::RGB:
return 3;
default:
TODO();
}
}
ErrorOr<Color> read_color(BigEndianInputBitStream& stream)
{
auto bits_per_sample = *m_metadata.bits_per_sample();
// Section 7: Additional Baseline TIFF Requirements
// Some TIFF files may have more components per pixel than you think. A Baseline TIFF reader must skip over
// them gracefully, using the values of the SamplesPerPixel and BitsPerSample fields.
auto discard_unknown_channels = [&]() -> ErrorOr<void> {
auto const unknown_channels = *m_metadata.samples_per_pixel() - samples_for_photometric_interpretation();
for (u8 i = bits_per_sample.size() - unknown_channels; i < bits_per_sample.size(); ++i)
TRY(read_component(stream, bits_per_sample[i]));
return {};
};
if (m_metadata.photometric_interpretation() == PhotometricInterpretation::RGB) {
auto const first_component = TRY(read_component(stream, bits_per_sample[0]));
auto const second_component = TRY(read_component(stream, bits_per_sample[1]));
auto const third_component = TRY(read_component(stream, bits_per_sample[2]));
TRY(discard_unknown_channels());
return Color(first_component, second_component, third_component);
}
@ -104,6 +129,7 @@ private:
if (m_metadata.photometric_interpretation() == PhotometricInterpretation::WhiteIsZero)
luminosity = ~luminosity;
TRY(discard_unknown_channels());
return Color(luminosity, luminosity, luminosity);
}