xti extensions

[wxWidgets.git] / src / common / imagpng.cpp

diff --git a/src/common/imagpng.cpp b/src/common/imagpng.cpp
index 66e917422ac619472ba14fdff90bba0a21471017..99db62ed93b5d66045e1a9479f7475e3652eef75 100644 (file)
--- a/src/common/imagpng.cpp
+++ b/src/common/imagpng.cpp
@@ -220,14 +220,13 @@ CheckTransparency(unsigned char **lines,
                   png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h,
                   size_t numColBytes)
 {
-    // we start from (x + 1, y)
-    x++;
-
     // suppose that a mask will suffice and check all the remaining alpha
     // values to see if it does
     for ( ; y < h; y++ )
     {
-        unsigned const char *ptr = lines[y] + x;
+        // each pixel is numColBytes+1 bytes, offset into the current line by
+        // the current x position
+        unsigned const char *ptr = lines[y] + (x * (numColBytes + 1));
 
         for ( png_uint_32 x2 = x; x2 < w; x2++ )
         {