Merge 3a3ee7f into ef4a0b2

python-pillow · Jan 9, 2020 · f25cd1b · f25cd1b
2 parents ef4a0b2 + 3a3ee7f
commit f25cd1b
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Showing 3 changed files with 22 additions and 5 deletions.
diff --git a/Tests/images/dxt5-colorblock-alpha-issue-4142.dds b/Tests/images/dxt5-colorblock-alpha-issue-4142.dds
diff --git a/Tests/test_file_dds.py b/Tests/test_file_dds.py
@@ -149,6 +149,23 @@ def short_file():
 
         self.assertRaises(IOError, short_file)
 
+    def test_dxt5_colorblock_alpha_issue_4142(self):
+        """ Check that colorblocks that would count as black/transparent in DXT1 are decoded properly """
+
+        with Image.open("Tests/images/dxt5-colorblock-alpha-issue-4142.dds") as im:
+            px = im.getpixel((0, 0))
+            print(px)
+            self.assertFalse(px[0] == 0)
+            self.assertFalse(px[1] == 0)
+            self.assertFalse(px[2] == 0)
+
+            px = im.getpixel((1, 0))
+            print(px)
+            self.assertFalse(px[0] == 0)
+            self.assertFalse(px[1] == 0)
+            self.assertFalse(px[2] == 0)
+
+
     def test_unimplemented_pixel_format(self):
         self.assertRaises(
             NotImplementedError,

diff --git a/src/libImaging/BcnDecode.c b/src/libImaging/BcnDecode.c
@@ -69,7 +69,7 @@ static rgba decode_565(UINT16 x) {
 	return c;
 }
 
-static void decode_bc1_color(rgba *dst, const UINT8 *src) {
+static void decode_bc1_color(rgba *dst, const UINT8 *src, int separate_alpha) {
 	bc1_color col;
 	rgba p[4];
 	int n, cw;
@@ -84,7 +84,7 @@ static void decode_bc1_color(rgba *dst, const UINT8 *src) {
 	r1 = p[1].r;
 	g1 = p[1].g;
 	b1 = p[1].b;
-	if (col.c0 > col.c1) {
+	if (col.c0 > col.c1 || separate_alpha) {
 		p[2].r = (2*r0 + 1*r1) / 3;
 		p[2].g = (2*g0 + 1*g1) / 3;
 		p[2].b = (2*b0 + 1*b1) / 3;
@@ -148,12 +148,12 @@ static void decode_bc3_alpha(char *dst, const UINT8 *src, int stride, int o) {
 }
 
 static void decode_bc1_block(rgba *col, const UINT8* src) {
-	decode_bc1_color(col, src);
+	decode_bc1_color(col, src, 0);
 }
 
 static void decode_bc2_block(rgba *col, const UINT8* src) {
 	int n, bitI, byI, av;
-	decode_bc1_color(col, src + 8);
+	decode_bc1_color(col, src + 8, 1);
 	for (n = 0; n < 16; n++) {
 		bitI = n * 4;
 		byI = bitI >> 3;
@@ -164,7 +164,7 @@ static void decode_bc2_block(rgba *col, const UINT8* src) {
 }
 
 static void decode_bc3_block(rgba *col, const UINT8* src) {
-	decode_bc1_color(col, src + 8);
+	decode_bc1_color(col, src + 8, 1);
 	decode_bc3_alpha((char *)col, src, sizeof(col[0]), 3);
 }