test/utils.c: Clip values to the [0, 255] interval

Unpremultiplying a superluminescent pixel can result in values greater
than 255.

diff --git a/test/utils.c b/test/utils.c
index cc0365a..c1bf6dc 100644 (file)
--- a/test/utils.c
+++ b/test/utils.c
@@ -358,9 +358,16 @@ a8r8g8b8_to_rgba_np (uint32_t *dst, uint32_t *src, int n_pixels)
 
        if (a != 0)
        {
-           r = (r * 255) / a;
-           g = (g * 255) / a;
-           b = (b * 255) / a;
+#define DIVIDE(c, a)                                                   \
+           do                                                          \
+           {                                                           \
+               int t = ((c) * 255) / a;                                \
+               (c) = t < 0? 0 : t > 255? 255 : t;                      \
+           } while (0)
+
+           DIVIDE (r, a);
+           DIVIDE (g, a);
+           DIVIDE (b, a);
        }
 
        *dst8++ = r;