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Add tint operation to set image chroma

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This commit is contained in:
Rik Heywood
2018-04-11 20:05:48 +01:00
committed by Lovell Fuller
parent bdac5b5807
commit dbac4b9a63
15 changed files with 172 additions and 23 deletions
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26
src/operations.cc
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@@ -152,6 +152,32 @@ namespace sharp {
return dst.bandjoin(mask.cast(dst.format()));
}
/*
* Tint an image using the specified chroma, preserving the original image luminance
*/
VImage Tint(VImage image, double const a, double const b) {
// Get original colourspace
VipsInterpretation typeBeforeTint = image.interpretation();
if (typeBeforeTint == VIPS_INTERPRETATION_RGB) {
typeBeforeTint = VIPS_INTERPRETATION_sRGB;
}
// Create 2 band image with every pixel set to the tint chroma
std::vector<double> chromaPixel {a, b};
VImage chroma = image.new_from_image(chromaPixel);
// Extract luminance
VImage luminance = image.colourspace(VIPS_INTERPRETATION_LAB)[0];
// Create the tinted version by combining the L from the original and the chroma from the tint
VImage tinted = luminance.bandjoin(chroma).colourspace(typeBeforeTint);
// Attach original alpha channel, if any
if (HasAlpha(image)) {
// Extract original alpha channel
VImage alpha = image[image.bands() - 1];
// Join alpha channel to normalised image
tinted = tinted.bandjoin(alpha);
}
return tinted;
}
/*
* Stretch luminance to cover full dynamic range.
*/