Mathis/sharp
1
0
Fork 0
mirror of https://github.com/lovell/sharp.git synced 2026-02-06 06:36:17 +01:00
Code Issues Packages Projects Releases Wiki Activity

overlayWith improvements: diff sizes/formats, gravity, buffer input

Browse Source
This commit is contained in:
Lovell Fuller
2016-02-29 14:30:29 +00:00
parent 55f204c6f9
commit d92ea31858
21 changed files with 407 additions and 242 deletions
Download Patch File Download Diff File Expand all files Collapse all files

49
src/operations.cc
View File

@@ -4,34 +4,49 @@
#include "operations.h"
using vips::VImage;
using vips::VError;
namespace sharp {
/*
Alpha composite src over dst
Assumes alpha channels are already premultiplied and will be unpremultiplied after
Alpha composite src over dst with given gravity.
Assumes alpha channels are already premultiplied and will be unpremultiplied after.
*/
VImage Composite(VImage src, VImage dst) {
VImage Composite(VImage src, VImage dst, const int gravity) {
using sharp::CalculateCrop;
using sharp::HasAlpha;
// Split src into non-alpha and alpha
if (!HasAlpha(src)) {
throw VError("Overlay image must have an alpha channel");
}
if (!HasAlpha(dst)) {
throw VError("Image to be overlaid must have an alpha channel");
}
if (src.width() > dst.width() || src.height() > dst.height()) {
throw VError("Overlay image must have same dimensions or smaller");
}
// Enlarge overlay src, if required
if (src.width() < dst.width() || src.height() < dst.height()) {
// Calculate the (left, top) coordinates of the output image within the input image, applying the given gravity.
int left;
int top;
std::tie(left, top) = CalculateCrop(dst.width(), dst.height(), src.width(), src.height(), gravity);
// Embed onto transparent background
std::vector<double> background { 0.0, 0.0, 0.0, 0.0 };
src = src.embed(left, top, dst.width(), dst.height(), VImage::option()
->set("extend", VIPS_EXTEND_BACKGROUND)
->set("background", background)
);
}
// Split src into non-alpha and alpha channels
VImage srcWithoutAlpha = src.extract_band(0, VImage::option()->set("n", src.bands() - 1));
VImage srcAlpha = src[src.bands() - 1] * (1.0 / 255.0);
// Split dst into non-alpha and alpha channels
VImage dstWithoutAlpha;
VImage dstAlpha;
if (HasAlpha(dst)) {
// Non-alpha: extract all-but-last channel
dstWithoutAlpha = dst.extract_band(0, VImage::option()->set("n", dst.bands() - 1));
// Alpha: Extract last channel
dstAlpha = dst[dst.bands() - 1] * (1.0 / 255.0);
} else {
// Non-alpha: Copy reference
dstWithoutAlpha = dst;
// Alpha: Use blank, opaque (0xFF) image
dstAlpha = VImage::black(dst.width(), dst.height()).invert();
}
VImage dstWithoutAlpha = dst.extract_band(0, VImage::option()->set("n", dst.bands() - 1));
VImage dstAlpha = dst[dst.bands() - 1] * (1.0 / 255.0);
//
// Compute normalized output alpha channel: