From f1edf87d04129b6ade9ef1eacf49ab4109fe1b14 Mon Sep 17 00:00:00 2001
From: Igor Sysoev <igor@sysoev.ru>
Date: Tue, 15 Sep 2009 09:47:12 +0000
Subject: [PATCH] fix alpha-channel transparency in PNG

---
 src/http/modules/ngx_http_image_filter_module.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/http/modules/ngx_http_image_filter_module.c b/src/http/modules/ngx_http_image_filter_module.c
index 653cc791b..70b27310c 100644
--- a/src/http/modules/ngx_http_image_filter_module.c
+++ b/src/http/modules/ngx_http_image_filter_module.c
@@ -768,6 +768,11 @@ ngx_http_image_resize(ngx_http_request_t *r, ngx_http_image_filter_ctx_t *ctx)
             return NULL;
         }
 
+        if (colors == 0) {
+            gdImageSaveAlpha(dst, 1);
+            gdImageAlphaBlending(dst, 0);
+        }
+
         gdImageCopyResampled(dst, src, 0, 0, 0, 0, dx, dy, sx, sy);
 
         gdImageDestroy(src);
@@ -810,6 +815,11 @@ ngx_http_image_resize(ngx_http_request_t *r, ngx_http_image_filter_ctx_t *ctx)
                            "image crop: %d x %d @ %d x %d",
                            dx, dy, ox, oy);
 
+            if (colors == 0) {
+                gdImageSaveAlpha(dst, 1);
+                gdImageAlphaBlending(dst, 0);
+            }
+
             gdImageCopy(dst, src, 0, 0, ox, oy, dx - ox, dy - oy);
 
             gdImageDestroy(src);