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Add removeAlpha op, removes alpha channel if any #1248

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This commit is contained in:
Lovell Fuller
2018-08-07 20:32:11 +01:00
parent 25bd2cea3e
commit c14434f9e7
10 changed files with 93 additions and 24 deletions
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18
src/operations.cc
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@@ -28,6 +28,16 @@ using vips::VError;
namespace sharp {
/*
Removes alpha channel, if any.
*/
VImage RemoveAlpha(VImage image) {
if (HasAlpha(image)) {
image = image.extract_band(0, VImage::option()->set("n", image.bands() - 1));
}
return image;
}
/*
Composite overlayImage over image at given position
Assumes alpha channels are already premultiplied and will be unpremultiplied after
@@ -223,10 +233,8 @@ namespace sharp {
VImage Gamma(VImage image, double const exponent) {
if (HasAlpha(image)) {
// Separate alpha channel
VImage imageWithoutAlpha = image.extract_band(0,
VImage::option()->set("n", image.bands() - 1));
VImage alpha = image[image.bands() - 1];
return imageWithoutAlpha.gamma(VImage::option()->set("exponent", exponent)).bandjoin(alpha);
return RemoveAlpha(image).gamma(VImage::option()->set("exponent", exponent)).bandjoin(alpha);
} else {
return image.gamma(VImage::option()->set("exponent", exponent));
}
@@ -374,10 +382,8 @@ namespace sharp {
VImage Linear(VImage image, double const a, double const b) {
if (HasAlpha(image)) {
// Separate alpha channel
VImage imageWithoutAlpha = image.extract_band(0,
VImage::option()->set("n", image.bands() - 1));
VImage alpha = image[image.bands() - 1];
return imageWithoutAlpha.linear(a, b).bandjoin(alpha);
return RemoveAlpha(image).linear(a, b).bandjoin(alpha);
} else {
return image.linear(a, b);
}