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Alpha compositing: support grey+alpha src and non-alpha dst

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Lovell Fuller
2015-06-02 14:34:23 +01:00
parent 36be0453dd
commit 1091be374e
10 changed files with 133 additions and 90 deletions
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46
src/pipeline.cc
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@@ -484,9 +484,6 @@ class PipelineWorker : public NanAsyncWorker {
}
}
// Premultiply image alpha channel before all transformations to avoid
// dark fringing around bright pixels
// See: http://entropymine.com/imageworsener/resizealpha/
bool shouldAffineTransform = xresidual != 0.0 || yresidual != 0.0;
bool shouldBlur = baton->blurSigma != 0.0;
bool shouldSharpen = baton->sharpenRadius != 0;
@@ -494,13 +491,15 @@ class PipelineWorker : public NanAsyncWorker {
bool hasOverlay = !baton->overlayPath.empty();
bool shouldPremultiplyAlpha = HasAlpha(image) && image->Bands == 4 && (shouldTransform || hasOverlay);
// Premultiply image alpha channel before all transformations to avoid
// dark fringing around bright pixels
// See: http://entropymine.com/imageworsener/resizealpha/
if (shouldPremultiplyAlpha) {
VipsImage *imagePremultiplied;
if (Premultiply(hook, image, &imagePremultiplied)) {
(baton->err).append("Failed to premultiply alpha channel.");
return Error();
}
vips_object_local(hook, imagePremultiplied);
image = imagePremultiplied;
}
@@ -820,41 +819,34 @@ class PipelineWorker : public NanAsyncWorker {
if (overlayImageType != ImageType::UNKNOWN) {
overlayImage = InitImage(baton->overlayPath.c_str(), baton->accessMethod);
if (overlayImage == NULL) {
(baton->err).append("Overlay input file has corrupt header");
overlayImageType = ImageType::UNKNOWN;
(baton->err).append("Overlay image has corrupt header");
return Error();
} else {
vips_object_local(hook, overlayImage);
}
} else {
(baton->err).append("Overlay input file is of an unsupported image format");
}
if (overlayImage == NULL || overlayImageType == ImageType::UNKNOWN) {
(baton->err).append("Overlay image is of an unsupported image format");
return Error();
}
if (!HasAlpha(overlayImage)) {
(baton->err).append("Overlay input must have an alpha channel");
(baton->err).append("Overlay image must have an alpha channel");
return Error();
}
if (overlayImage->Xsize != image->Xsize && overlayImage->Ysize != image->Ysize) {
(baton->err).append("Overlay image must have same dimensions as resized image");
return Error();
}
if (!HasAlpha(image)) {
(baton->err).append("Input image must have an alpha channel");
return Error();
}
if (overlayImage->Bands != 4) {
(baton->err).append("Overlay input image must have 4 channels");
return Error();
}
if (image->Bands != 4) {
(baton->err).append("Input image must have 4 channels");
// Ensure overlay is sRGB
VipsImage *overlayImageRGB;
if (vips_colourspace(overlayImage, &overlayImageRGB, VIPS_INTERPRETATION_sRGB, NULL)) {
return Error();
}
vips_object_local(hook, overlayImageRGB);
// Premultiply overlay
VipsImage *overlayImagePremultiplied;
if (Premultiply(hook, overlayImage, &overlayImagePremultiplied)) {
if (Premultiply(hook, overlayImageRGB, &overlayImagePremultiplied)) {
(baton->err).append("Failed to premultiply alpha channel of overlay image.");
return Error();
}
@@ -883,14 +875,14 @@ class PipelineWorker : public NanAsyncWorker {
// Convert image to sRGB, if not already
if (image->Type != VIPS_INTERPRETATION_sRGB) {
// Switch intrepretation to sRGB
// Switch interpretation to sRGB
VipsImage *rgb;
if (vips_colourspace(image, &rgb, VIPS_INTERPRETATION_sRGB, NULL)) {
return Error();
}
vips_object_local(hook, rgb);
image = rgb;
// Tranform colours from embedded profile to sRGB profile
// Transform colours from embedded profile to sRGB profile
if (baton->withMetadata && HasProfile(image)) {
VipsImage *profiled;
if (vips_icc_transform(image, &profiled, srgbProfile.c_str(), "embedded", TRUE, NULL)) {