Fix bug with non-paletted transparent PNGs

Adapted from a fix by YAMAMOTO Mitsuharu (Bug#37153#77).
* src/image.c (png_load_body): Fix bug with non-paletted
transparent images.

1 files changed, 9 insertions, 8 deletions

diff --git a/src/image.c b/src/image.c
index 18495612e98..fe7bd90b051 100644
--- a/src/image.c
+++ b/src/image.c
@@ -6598,15 +6598,16 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
 # ifdef PNG_tRNS_SUPPORTED
   png_bytep trans_alpha;
   int num_trans;
-  if (png_get_tRNS (png_ptr, info_ptr, &trans_alpha, &num_trans, NULL)
-      && trans_alpha)
+  if (png_get_tRNS (png_ptr, info_ptr, &trans_alpha, &num_trans, NULL))
     {
-      int i;
-      for (i = 0; i < num_trans; i++)
-        if (0 < trans_alpha[i] && trans_alpha[i] < 255)
-          break;
-      if (! (i < num_trans))
-        transparent_p = true;
+      transparent_p = true;
+      if (trans_alpha)
+        for (int i = 0; i < num_trans; i++)
+          if (0 < trans_alpha[i] && trans_alpha[i] < 255)
+            {
+              transparent_p = false;
+              break;
+            }
     }
 # endif