Merge pull request #737 from libgd/bug/405

Fix #405, -1 aims to reset the transparent color; refactor a bit; add test to existing test for -1

1 files changed, 17 insertions, 9 deletions

diff --git a/src/gd.c b/src/gd.c
index 4c1c3b6..db96cc9 100644
--- a/src/gd.c
+++ b/src/gd.c
@@ -895,19 +895,27 @@ BGD_DECLARE(void) gdImageColorDeallocate (gdImagePtr im, int color)
  */
 BGD_DECLARE(void) gdImageColorTransparent (gdImagePtr im, int color)
 {
-	if (color < 0) {
+	// Reset ::transparent
+	if (color == -1) {
+		im->transparent = -1;
 		return;
 	}
 
-	if (!im->trueColor) {
-		if (color >= gdMaxColors) {
-			return;
-		}
-		if (im->transparent != -1) {
-			im->alpha[im->transparent] = gdAlphaOpaque;
-		}
-		im->alpha[color] = gdAlphaTransparent;
+	if (color < -1) {
+		return;
+	}
+
+	if (im->trueColor) {
+		im->transparent = color;
+		return;
+	}
+
+	// Palette Image
+	if (color >= gdMaxColors) {
+		return;
 	}
+	im->alpha[im->transparent] = gdAlphaOpaque;
+	im->alpha[color] = gdAlphaTransparent;
 	im->transparent = color;
 }