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Avoid (un)premultiplication for overlay image without alpha channel

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Add 'premultiplied' boolean attribute to output info, helps test
This commit is contained in:
Lovell Fuller
2017-03-25 16:52:09 +00:00
parent 301bfbd271
commit 1169afbe90
11 changed files with 109 additions and 104 deletions
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71
src/pipeline.cc
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@@ -333,12 +333,20 @@ class PipelineWorker : public Nan::AsyncWorker {
image = image.colourspace(VIPS_INTERPRETATION_B_W);
}
// 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));
// Ensure image has an alpha channel when there is an overlay with an alpha channel
VImage overlayImage;
ImageType overlayImageType = ImageType::UNKNOWN;
bool shouldOverlayWithAlpha = FALSE;
if (baton->overlay != nullptr) {
std::tie(overlayImage, overlayImageType) = OpenInput(baton->overlay, baton->accessMethod);
if (HasAlpha(overlayImage)) {
shouldOverlayWithAlpha = !baton->overlayCutout;
if (!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;
@@ -346,9 +354,8 @@ class PipelineWorker : public Nan::AsyncWorker {
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));
(shouldShrink || shouldReduce || shouldBlur || shouldConv || shouldSharpen || shouldOverlayWithAlpha);
// Premultiply image alpha channel before all transformations to avoid
// dark fringing around bright pixels
@@ -584,10 +591,11 @@ class PipelineWorker : public Nan::AsyncWorker {
}
// Composite with overlay, if present
if (hasOverlay) {
VImage overlayImage;
ImageType overlayImageType = ImageType::UNKNOWN;
std::tie(overlayImage, overlayImageType) = OpenInput(baton->overlay, baton->accessMethod);
if (baton->overlay != nullptr) {
// Verify overlay image is within current dimensions
if (overlayImage.width() > image.width() || overlayImage.height() > image.height()) {
throw vips::VError("Overlay image must have same dimensions or smaller");
}
// Check if overlay is tiled
if (baton->overlayTile) {
int const overlayImageWidth = overlayImage.width();
@@ -620,31 +628,34 @@ class PipelineWorker : public Nan::AsyncWorker {
// the overlayGravity was used for extract_area, therefore set it back to its default value of 0
baton->overlayGravity = 0;
}
if (shouldCutout) {
if (baton->overlayCutout) {
// 'cut out' the image, premultiplication is not required
image = sharp::Cutout(overlayImage, image, baton->overlayGravity);
} else {
// Ensure overlay has alpha channel
if (!HasAlpha(overlayImage)) {
double const multiplier = sharp::Is16Bit(overlayImage.interpretation()) ? 256.0 : 1.0;
overlayImage = overlayImage.bandjoin(
VImage::new_matrix(overlayImage.width(), overlayImage.height()).new_from_image(255 * multiplier));
// Ensure overlay is sRGB
overlayImage = overlayImage.colourspace(VIPS_INTERPRETATION_sRGB);
// Ensure overlay matches premultiplication state
if (shouldPremultiplyAlpha) {
// Ensure overlay has alpha channel
if (!HasAlpha(overlayImage)) {
double const multiplier = sharp::Is16Bit(overlayImage.interpretation()) ? 256.0 : 1.0;
overlayImage = overlayImage.bandjoin(
VImage::new_matrix(overlayImage.width(), overlayImage.height()).new_from_image(255 * multiplier));
}
overlayImage = overlayImage.premultiply();
}
// Ensure image has alpha channel
if (!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));
}
// Ensure overlay is premultiplied sRGB
overlayImage = overlayImage.colourspace(VIPS_INTERPRETATION_sRGB).premultiply();
int left;
int top;
if (baton->overlayXOffset >= 0 && baton->overlayYOffset >= 0) {
// Composite images with given offsets
image = sharp::Composite(overlayImage, image, baton->overlayXOffset, baton->overlayYOffset);
// Composite images at given offsets
std::tie(left, top) = sharp::CalculateCrop(image.width(), image.height(),
overlayImage.width(), overlayImage.height(), baton->overlayXOffset, baton->overlayYOffset);
} else {
// Composite images with given gravity
image = sharp::Composite(overlayImage, image, baton->overlayGravity);
std::tie(left, top) = sharp::CalculateCrop(image.width(), image.height(),
overlayImage.width(), overlayImage.height(), baton->overlayGravity);
}
image = sharp::Composite(image, overlayImage, left, top);
}
}
@@ -658,6 +669,7 @@ class PipelineWorker : public Nan::AsyncWorker {
image = image.cast(VIPS_FORMAT_UCHAR);
}
}
baton->premultiplied = shouldPremultiplyAlpha;
// Gamma decoding (brighten)
if (baton->gamma >= 1 && baton->gamma <= 3) {
@@ -942,6 +954,7 @@ class PipelineWorker : public Nan::AsyncWorker {
Set(info, New("width").ToLocalChecked(), New<v8::Uint32>(static_cast<uint32_t>(width)));
Set(info, New("height").ToLocalChecked(), New<v8::Uint32>(static_cast<uint32_t>(height)));
Set(info, New("channels").ToLocalChecked(), New<v8::Uint32>(static_cast<uint32_t>(baton->channels)));
Set(info, New("premultiplied").ToLocalChecked(), New<v8::Boolean>(baton->premultiplied));
if (baton->cropCalcLeft != -1 && baton->cropCalcLeft != -1) {
Set(info, New("cropCalcLeft").ToLocalChecked(), New<v8::Uint32>(static_cast<uint32_t>(baton->cropCalcLeft)));
Set(info, New("cropCalcTop").ToLocalChecked(), New<v8::Uint32>(static_cast<uint32_t>(baton->cropCalcTop)));