Mathis/sharp
1
0
Fork 0
mirror of https://github.com/lovell/sharp.git synced 2025-12-19 07:15:08 +01:00
Code Issues Packages Projects Releases Wiki Activity

Ensure premultiply op occurs before box shrink #605

Browse Source
This commit is contained in:
Lovell Fuller
2016-12-04 18:25:44 +00:00
parent 7231d92d1f
commit d3c78f825c
11 changed files with 42 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/operations.cc
View File

@@ -300,6 +300,12 @@ namespace sharp {
Calculate the intensity of edges, skin tone and saturation
*/
double AttentionStrategy::operator()(VImage image) {
// Flatten RGBA onto a mid-grey background
if (image.bands() == 4 && HasAlpha(image)) {
double const midgrey = sharp::Is16Bit(image.interpretation()) ? 32768.0 : 128.0;
std::vector<double> background { midgrey, midgrey, midgrey };
image = image.flatten(VImage::option()->set("background", background));
}
// Convert to LAB colourspace
VImage lab = image.colourspace(VIPS_INTERPRETATION_LAB);
VImage l = lab[0];

60
src/pipeline.cc
View File

@@ -290,9 +290,6 @@ class PipelineWorker : public Nan::AsyncWorker {
);
}
// Calculate maximum alpha value based on input image pixel depth
double const maxAlpha = sharp::MaximumImageAlpha(image.interpretation());
// Flatten image to remove alpha channel
if (baton->flatten && HasAlpha(image)) {
// Scale up 8-bit values to match 16-bit input image
@@ -305,7 +302,6 @@ class PipelineWorker : public Nan::AsyncWorker {
};
image = image.flatten(VImage::option()
->set("background", background)
->set("max_alpha", maxAlpha)
);
}
@@ -324,7 +320,33 @@ class PipelineWorker : public Nan::AsyncWorker {
image = image.colourspace(VIPS_INTERPRETATION_B_W);
}
if (xshrink > 1 || yshrink > 1) {
// Ensure image has an alpha channel when there is an overlay
bool hasOverlay = baton->overlay != nullptr;
if (hasOverlay && !HasAlpha(image)) {
double const multiplier = sharp::Is16Bit(image.interpretation()) ? 256.0 : 1.0;
image = image.bandjoin(
VImage::new_matrix(image.width(), image.height()).new_from_image(255 * multiplier)
);
}
bool const shouldShrink = xshrink > 1 || yshrink > 1;
bool const shouldReduce = xresidual != 1.0 || yresidual != 1.0;
bool const shouldBlur = baton->blurSigma != 0.0;
bool const shouldConv = baton->convKernelWidth * baton->convKernelHeight > 0;
bool const shouldSharpen = baton->sharpenSigma != 0.0;
bool const shouldCutout = baton->overlayCutout;
bool const shouldPremultiplyAlpha = HasAlpha(image) &&
(shouldShrink || shouldReduce || shouldBlur || shouldConv || shouldSharpen || (hasOverlay && !shouldCutout));
// Premultiply image alpha channel before all transformations to avoid
// dark fringing around bright pixels
// See: http://entropymine.com/imageworsener/resizealpha/
if (shouldPremultiplyAlpha) {
image = image.premultiply();
}
// Fast, integral box-shrink
if (shouldShrink) {
if (yshrink > 1) {
image = image.shrinkv(yshrink);
}
@@ -349,32 +371,8 @@ class PipelineWorker : public Nan::AsyncWorker {
}
}
// Ensure image has an alpha channel when there is an overlay
bool hasOverlay = baton->overlay != nullptr;
if (hasOverlay && !HasAlpha(image)) {
double const multiplier = sharp::Is16Bit(image.interpretation()) ? 256.0 : 1.0;
image = image.bandjoin(
VImage::new_matrix(image.width(), image.height()).new_from_image(255 * multiplier)
);
}
bool shouldAffineTransform = xresidual != 1.0 || yresidual != 1.0;
bool shouldBlur = baton->blurSigma != 0.0;
bool shouldConv = baton->convKernelWidth * baton->convKernelHeight > 0;
bool shouldSharpen = baton->sharpenSigma != 0.0;
bool shouldCutout = baton->overlayCutout;
bool shouldPremultiplyAlpha = HasAlpha(image) &&
(shouldAffineTransform || shouldBlur || shouldConv || shouldSharpen || (hasOverlay && !shouldCutout));
// Premultiply image alpha channel before all transformations to avoid
// dark fringing around bright pixels
// See: http://entropymine.com/imageworsener/resizealpha/
if (shouldPremultiplyAlpha) {
image = image.premultiply(VImage::option()->set("max_alpha", maxAlpha));
}
// Use affine increase or kernel reduce with the remaining float part
if (shouldAffineTransform) {
if (xresidual != 1.0 || yresidual != 1.0) {
// Insert tile cache to prevent over-computation of previous operations
if (baton->accessMethod == VIPS_ACCESS_SEQUENTIAL) {
image = sharp::TileCache(image, yresidual);
@@ -651,7 +649,7 @@ class PipelineWorker : public Nan::AsyncWorker {
// Reverse premultiplication after all transformations:
if (shouldPremultiplyAlpha) {
image = image.unpremultiply(VImage::option()->set("max_alpha", maxAlpha));
image = image.unpremultiply();
// Cast pixel values to integer
if (sharp::Is16Bit(image.interpretation())) {
image = image.cast(VIPS_FORMAT_USHORT);