Bug #23815: Added ImageCopyMergeAlpha

ext/gd/gd.c

@@ -704,7 +704,17 @@ ZEND_BEGIN_ARG_INFO(arginfo_imagecopymerge, 0)
 	ZEND_ARG_INFO(0, src_h)
 	ZEND_ARG_INFO(0, pct)
 ZEND_END_ARG_INFO()
-
+ZEND_BEGIN_ARG_INFO(arginfo_imagecopymergealpha, 0)
+	ZEND_ARG_INFO(0, src_im)
+	ZEND_ARG_INFO(0, dst_im)
+	ZEND_ARG_INFO(0, dst_x)
+	ZEND_ARG_INFO(0, dst_y)
+	ZEND_ARG_INFO(0, src_x)
+	ZEND_ARG_INFO(0, src_y)
+	ZEND_ARG_INFO(0, src_w)
+	ZEND_ARG_INFO(0, src_h)
+	ZEND_ARG_INFO(0, pct)
+ZEND_END_ARG_INFO()
 ZEND_BEGIN_ARG_INFO(arginfo_imagecopymergegray, 0)
 	ZEND_ARG_INFO(0, src_im)
 	ZEND_ARG_INFO(0, dst_im)
@@ -917,6 +927,7 @@ const zend_function_entry gd_functions[] = {
 	PHP_FE(imagecopy,								arginfo_imagecopy)
 #if HAVE_LIBGD15
 	PHP_FE(imagecopymerge,							arginfo_imagecopymerge)
+	PHP_FE(imagecopymergealpha,						arginfo_imagecopymergealpha)
 	PHP_FE(imagecopymergegray,						arginfo_imagecopymergegray)
 #endif
 	PHP_FE(imagecopyresized,						arginfo_imagecopyresized)
@@ -3779,6 +3790,35 @@ PHP_FUNCTION(imagecopymerge)
 }
 /* }}} */
 
+/* {{{ proto bool imagecopymergealpha(resource src_im, resource dst_im, int dst_x, int dst_y, int src_x, int src_y, int src_w, int src_h, int pct)
+   Merge one part of an image with another -while preserving Alpha channel*/
+PHP_FUNCTION(imagecopymergealpha)
+{
+	zval *SIM, *DIM;
+	long SX, SY, SW, SH, DX, DY, PCT;
+	gdImagePtr im_dst, im_src;
+	int srcH, srcW, srcY, srcX, dstY, dstX, pct;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "rrlllllll", &DIM, &SIM, &DX, &DY, &SX, &SY, &SW, &SH, &PCT) == FAILURE) {
+		return;
+	}
+
+	ZEND_FETCH_RESOURCE(im_src, gdImagePtr, &SIM, -1, "Image", le_gd);
+	ZEND_FETCH_RESOURCE(im_dst, gdImagePtr, &DIM, -1, "Image", le_gd);
+
+	srcX = SX;
+	srcY = SY;
+	srcH = SH;
+	srcW = SW;
+	dstX = DX;
+	dstY = DY;
+	pct  = PCT;
+
+	gdImageCopyMergeAlpha(im_dst, im_src, dstX, dstY, srcX, srcY, srcW, srcH, pct);
+	RETURN_TRUE;
+}
+/* }}} */
+
 /* {{{ proto bool imagecopymergegray(resource src_im, resource dst_im, int dst_x, int dst_y, int src_x, int src_y, int src_w, int src_h, int pct)
    Merge one part of an image with another */
 PHP_FUNCTION(imagecopymergegray)

ext/gd/libgd/gd.c

@@ -2285,6 +2285,82 @@ void gdImageCopyMerge (gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int s
 	}
 }
 
+/* This function is a real alpha channel operations,
+   but it has restrictions. */
+void gdImageCopyMergeAlpha (gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int srcX, int srcY, int w, int h, int pct)
+{
+	int c;
+	int x, y;
+	int toy;
+	toy = dstY;
+
+	if (pct == 100) {
+		/* no opacity adjustment required pass through to gdImageCopy() */
+		gdImageCopy(dst, src, dstX, dstY, srcX, srcY, w, h);
+		return;
+	}
+
+	if (pct == 0) {
+		/* 0% opacity? nothing needs to be done */
+		return;
+	}
+
+	if (src->trueColor && dst->trueColor) {
+		/* support for maintaining the alpha (transparency) of both source and
+		 * destination images (assuming they are true colour) while opacity blending.
+		 */
+		int         ca, cr, cg, cb, nc;
+		float       na;
+		float       ac;
+
+		/* we need to loop through the src image to get the max transparency level */
+		int mt = 0;
+
+		for (y = 0; y < h; y++) {
+			for (x = 0; x < w; x++) {
+				c  = gdImageGetTrueColorPixel (src, srcX + x, srcY + y);
+				ca = gdImageAlpha(src, c);
+
+				mt = ca > mt ? ca : mt;
+			}
+		}
+
+		if (mt < (gdAlphaMax / 2)) {
+			mt = gdAlphaMax - mt;
+		}
+
+		/* alpha correction factor */
+		ac = (float)mt / gdAlphaMax;
+
+		/* loop through the image again and set/adjust alpha channel level */
+		for (y = 0; y < h; y++) {
+			for (x = 0; x < w; x++) {
+				c  = gdImageGetTrueColorPixel (src, srcX + x, srcY + y);
+				ca = gdImageAlpha(src, c);
+				cr = gdImageRed(src, c);
+				cg = gdImageGreen(src, c);
+				cb = gdImageBlue(src, c);
+
+				na = (ca + gdAlphaMax - (gdAlphaMax * ((float)pct / 100))) * ac;
+				na = (na > gdAlphaMax) ? gdAlphaMax : ((na < gdAlphaOpaque) ? gdAlphaOpaque: na);
+
+				nc = gdImageColorAllocateAlpha(dst, cr, cg, cb, (int)na);
+				if (nc == -1) {
+					gdImageColorClosestAlpha(dst, cr, cg, cb, (int)na);
+				}
+
+				/* set pixel on destination image */
+				gdImageSetPixel (dst, dstX + x, dstY + y, nc);
+			}
+		}
+
+		return;
+	}
+
+	/* falback */
+	gdImageCopyMerge(dst, src, dstX, dstY, srcX, srcY, w, h, pct);
+}
+
 /* This function is a substitute for real alpha channel operations,
    so it doesn't pay attention to the alpha channel. */
 void gdImageCopyMergeGray (gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int srcX, int srcY, int w, int h, int pct)

ext/gd/libgd/gdtest.c

@@ -250,6 +250,9 @@ main (int argc, char **argv)
   gdImageCopyMerge (im2, im3, 150, 200, 10, 10, 90, 50, 50);
   gdImageCopyMerge (im2, im3, 180, 70, 10, 10, 90, 50, 50);
 
+  gdImageCopyMergeAlpha (im2, im3, 150, 200, 10, 10, 90, 50, 50);
+  gdImageCopyMergeAlpha (im2, im3, 180, 70, 10, 10, 90, 50, 50);
+
   gdImageCopyMergeGray (im2, im3, 250, 160, 10, 10, 90, 50, 50);
   gdImageCopyMergeGray (im2, im3, 80, 70, 10, 10, 90, 50, 50);
 

ext/gd/php_gd.h

@@ -96,6 +96,7 @@ PHP_FUNCTION(imagecolorsforindex);
 PHP_FUNCTION(imagecolortransparent);
 PHP_FUNCTION(imagecopy);
 PHP_FUNCTION(imagecopymerge);
+PHP_FUNCTION(imagecopymergealpha);
 PHP_FUNCTION(imagecopyresized);
 PHP_FUNCTION(imagetypes);
 PHP_FUNCTION(imagecreate);

ext/gd/tests/imagecopymergealpha_basic.phpt

@@ -0,0 +1,40 @@
+--TEST--
+Testing imagecopymergealpha() of GD library
+--CREDITS--
+Matt Clegg <cleggmatt [at] gmail [dot] com>
+Orignally by: redmonkey
+--SKIPIF--
+<?php 
+if (!extension_loaded("gd")) die("skip GD not present");
+?>
+--FILE--
+<?php
+
+$images=array(
+        'imagecopymerge'=>1,
+        'imagecopymergealpha'=>2
+);
+
+foreach ($images as $f=>$md5){
+
+$bg  = imagecreatefrompng('tux.png');
+$over = imagecreatefrompng('ff-logo-sm.png');
+imagealphablending($bg, true);
+imagesavealpha($bg, true);
+$f($bg, $over, 276, 300, 0, 0, 123, 119, 50);
+
+ob_start();
+imagepng($bg);
+$dump = "$f: ".md5(ob_get_contents())."\n";
+ob_end_clean();
+
+echo $dump;
+
+}
+
+
+?>
+--EXPECTF--
+imagecopymerge: 8e5cf51d6f59e9cea8572bfac47b5668
+imagecopymergealpha: f685c4a30c4255de4290c928ab4ac05e
+