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Ensure 16-bit+alpha input images work with vips_premultiply #301

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Improves SVG support as *magick serves these as 16-bit

Add automated tests for SVG and 16-bit+alpha PNG inputs
This commit is contained in:
Lovell Fuller
2015-11-21 20:21:34 +00:00
parent c9ecc7a517
commit 05dd191e17
7 changed files with 46 additions and 9 deletions
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36
src/pipeline.cc
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@@ -437,17 +437,22 @@ class PipelineWorker : public AsyncWorker {
image = transformed;
}
// Calculate maximum alpha value based on input image pixel depth
double maxAlpha = (image->BandFmt == VIPS_FORMAT_USHORT) ? 65535.0 : 255.0;
// Flatten image to remove alpha channel
if (baton->flatten && HasAlpha(image)) {
// Scale up 8-bit values to match 16-bit input image
double multiplier = (image->Type == VIPS_INTERPRETATION_RGB16) ? 256.0 : 1.0;
// Background colour
VipsArrayDouble *background = vips_array_double_newv(
3, // Ignore alpha channel as we're about to remove it
baton->background[0],
baton->background[1],
baton->background[2]
baton->background[0] * multiplier,
baton->background[1] * multiplier,
baton->background[2] * multiplier
);
VipsImage *flattened;
if (vips_flatten(image, &flattened, "background", background, nullptr)) {
if (vips_flatten(image, &flattened, "background", background, "max_alpha", maxAlpha, nullptr)) {
vips_area_unref(reinterpret_cast<VipsArea*>(background));
return Error();
}
@@ -526,7 +531,7 @@ class PipelineWorker : public AsyncWorker {
// See: http://entropymine.com/imageworsener/resizealpha/
if (shouldPremultiplyAlpha) {
VipsImage *imagePremultiplied;
if (vips_premultiply(image, &imagePremultiplied, nullptr)) {
if (vips_premultiply(image, &imagePremultiplied, "max_alpha", maxAlpha, nullptr)) {
(baton->err).append("Failed to premultiply alpha channel.");
return Error();
}
@@ -792,7 +797,7 @@ class PipelineWorker : public AsyncWorker {
// Reverse premultiplication after all transformations:
if (shouldPremultiplyAlpha) {
VipsImage *imageUnpremultiplied;
if (vips_unpremultiply(image, &imageUnpremultiplied, nullptr)) {
if (vips_unpremultiply(image, &imageUnpremultiplied, "max_alpha", maxAlpha, nullptr)) {
(baton->err).append("Failed to unpremultiply alpha channel");
return Error();
}
@@ -820,7 +825,24 @@ class PipelineWorker : public AsyncWorker {
}
// Convert image to sRGB, if not already
if (image->Type != VIPS_INTERPRETATION_sRGB) {
if (image->Type == VIPS_INTERPRETATION_RGB16) {
// Ensure 16-bit integer
VipsImage *ushort;
if (vips_cast_ushort(image, &ushort, nullptr)) {
return Error();
}
vips_object_local(hook, ushort);
image = ushort;
// Fast conversion to 8-bit integer by discarding least-significant byte
VipsImage *msb;
if (vips_msb(image, &msb, nullptr)) {
return Error();
}
vips_object_local(hook, msb);
image = msb;
// Explicitly set to sRGB
image->Type = VIPS_INTERPRETATION_sRGB;
} else if (image->Type != VIPS_INTERPRETATION_sRGB) {
// Switch interpretation to sRGB
VipsImage *rgb;
if (vips_colourspace(image, &rgb, VIPS_INTERPRETATION_sRGB, nullptr)) {