X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/fd90675b89c7f0b8fb9c6749f8314a26e23b1b95..f645356813e0479e74db69e15e915384922001ea:/src/msw/dib.cpp?ds=sidebyside

diff --git a/src/msw/dib.cpp b/src/msw/dib.cpp
index 23ed673d49..14a44e2339 100644
--- a/src/msw/dib.cpp
+++ b/src/msw/dib.cpp
@@ -688,12 +688,14 @@ bool wxDIB::Create(const wxImage& image, PixelFormat pf)
         unsigned char *dst = dstLineStart;
         if ( alpha )
         {
+            int x;
+
             switch ( pf )
             {
                 case PixelFormat_PreMultiplied:
                     // Pre-multiply pixel values so that the DIB could be used
                     // with ::AlphaBlend().
-                    for ( int x = 0; x < w; x++ )
+                    for ( x = 0; x < w; x++ )
                     {
                         const unsigned char a = *alpha++;
                         *dst++ = (unsigned char)((src[2] * a + 127) / 255);
@@ -706,7 +708,7 @@ bool wxDIB::Create(const wxImage& image, PixelFormat pf)
 
                 case PixelFormat_NotPreMultiplied:
                     // Just copy pixel data without changing it.
-                    for ( int x = 0; x < w; x++ )
+                    for ( x = 0; x < w; x++ )
                     {
                         *dst++ = src[2];
                         *dst++ = src[1];
@@ -758,7 +760,14 @@ wxImage wxDIB::ConvertToImage() const
     }
 
     const int bpp = GetDepth();
+
+    // Remember if we have any "real" transparency, i.e. either any partially
+    // transparent pixels or not all pixels are fully opaque or fully
+    // transparent.
     bool hasAlpha = false;
+    bool hasOpaque = false;
+    bool hasTransparent = false;
+
     if ( bpp == 32 )
     {
         // 32 bit bitmaps may be either 0RGB or ARGB and we don't know in
@@ -791,13 +800,30 @@ wxImage wxDIB::ConvertToImage() const
                 // premultiplication done in Create() above
                 const unsigned char a = *src;
                 *alpha++ = a;
+
+                // Check what kind of alpha do we have.
+                switch ( a )
+                {
+                    case 0:
+                        hasTransparent = true;
+                        break;
+
+                    default:
+                        // Anything in between means we have real transparency
+                        // and must use alpha channel.
+                        hasAlpha = true;
+                        break;
+
+                    case 255:
+                        hasOpaque = true;
+                        break;
+                }
+
                 if ( a > 0 )
                 {
                     dst[0] = (dst[0] * 255) / a;
                     dst[1] = (dst[1] * 255) / a;
                     dst[2] = (dst[2] * 255) / a;
-
-                    hasAlpha = true;
                 }
 
                 src++;
@@ -815,6 +841,9 @@ wxImage wxDIB::ConvertToImage() const
         srcLineStart += srcBytesPerLine;
     }
 
+    if ( hasOpaque && hasTransparent )
+        hasAlpha = true;
+
     if ( !hasAlpha && image.HasAlpha() )
         image.ClearAlpha();