From 4e5f6f01a1b8dfd2dc07f760e79a0ced6d4836a5 Mon Sep 17 00:00:00 2001
From: Neil <nyamatongwe@gmail.com>
Date: Sat, 15 Feb 2020 12:47:29 +1100
Subject: Backport: Extract image conversion from RGBA to BGRA premultiplied
 into common function.

Backport of changeset 7987:beeac488af4d.
---
 gtk/PlatGTK.cxx | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

(limited to 'gtk')

diff --git a/gtk/PlatGTK.cxx b/gtk/PlatGTK.cxx
index 97009d4ff..f884ac565 100755
--- a/gtk/PlatGTK.cxx
+++ b/gtk/PlatGTK.cxx
@@ -597,18 +597,13 @@ void SurfaceImpl::DrawRGBAImage(PRectangle rc, int width, int height, const unsi
 		rc.top += (rc.Height() - height) / 2;
 	rc.bottom = rc.top + height;
 
-	int stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
+	const int stride = cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
 	const int ucs = stride * height;
 	std::vector<unsigned char> image(ucs);
-	for (int iy=0; iy<height; iy++) {
-		for (int ix=0; ix<width; ix++) {
-			unsigned char *pixel = &image[0] + iy*stride + ix * 4;
-			const unsigned char alpha = pixelsImage[3];
-			pixel[2] = (*pixelsImage++) * alpha / 255;
-			pixel[1] = (*pixelsImage++) * alpha / 255;
-			pixel[0] = (*pixelsImage++) * alpha / 255;
-			pixel[3] = *pixelsImage++;
-		}
+	for (ptrdiff_t iy=0; iy<height; iy++) {
+		unsigned char *pixel = &image[0] + iy*stride;
+		RGBAImage::BGRAFromRGBA(pixel, pixelsImage, width);
+		pixelsImage += RGBAImage::bytesPerPixel * width;
 	}
 
 	cairo_surface_t *psurfImage = cairo_image_surface_create_for_data(&image[0], CAIRO_FORMAT_ARGB32, width, height, stride);
-- 
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