- #39366, imagerotate does not use alpha with angles>45

ext/gd/libgd/gd.c

@@ -2776,6 +2776,9 @@ gdImagePtr gdImageRotate90 (gdImagePtr src, int ignoretransparent)
 	dst->transparent = src->transparent;
 
 	if (dst != NULL) {
+		int old_blendmode = dst->alphaBlendingFlag;
+		dst->alphaBlendingFlag = 0;
+
 		gdImagePaletteCopy (dst, src);
 
 		for (uY = 0; uY<src->sy; uY++) {
@@ -2795,6 +2798,7 @@ gdImagePtr gdImageRotate90 (gdImagePtr src, int ignoretransparent)
 				}
 			}
 		}
+		dst->alphaBlendingFlag = old_blendmode;
 	}
 
 	return dst;
@@ -2818,6 +2822,9 @@ gdImagePtr gdImageRotate180 (gdImagePtr src, int ignoretransparent)
 	dst->transparent = src->transparent;
 
 	if (dst != NULL) {
+		int old_blendmode = dst->alphaBlendingFlag;
+		dst->alphaBlendingFlag = 0;
+
 		gdImagePaletteCopy (dst, src);
 
 		for (uY = 0; uY<src->sy; uY++) {
@@ -2838,6 +2845,7 @@ gdImagePtr gdImageRotate180 (gdImagePtr src, int ignoretransparent)
 				}
 			}
 		}
+		dst->alphaBlendingFlag = old_blendmode;
 	}
 
 	return dst;
@@ -2861,6 +2869,9 @@ gdImagePtr gdImageRotate270 (gdImagePtr src, int ignoretransparent)
 	dst->transparent = src->transparent;
 
 	if (dst != NULL) {
+		int old_blendmode = dst->alphaBlendingFlag;
+		dst->alphaBlendingFlag = 0;
+
 		gdImagePaletteCopy (dst, src);
 
 		for (uY = 0; uY<src->sy; uY++) {
@@ -2881,6 +2892,7 @@ gdImagePtr gdImageRotate270 (gdImagePtr src, int ignoretransparent)
 				}
 			}
 		}
+		dst->alphaBlendingFlag = old_blendmode;
 	}
 
 	return dst;

ext/gd/tests/bug39366.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Bug #39366 (imagerotate does not respect alpha with angles>45)
+--SKIPIF--
+<?php 
+	if (!extension_loaded('gd')) die("skip gd extension not available\n"); 
+	if (!GD_BUNDLED) die('skip external GD libraries always fail');
+?>
+--FILE--
+<?php
+
+$im = imagecreatetruecolor(10,10);
+imagealphablending($im, 0);
+imagefilledrectangle($im, 0,0, 8,8, 0x32FF0000);
+$rotate = imagerotate($im, 180, 0);
+imagecolortransparent($rotate,0);
+imagesavealpha($rotate, true);
+$c = imagecolorat($rotate,5,5);
+printf("%X\n", $c);
+?>
+--EXPECTF--
+32FF0000