don't erase background in wxControl neither

[wxWidgets.git] / src / msw / dib.cpp

diff --git a/src/msw/dib.cpp b/src/msw/dib.cpp
index 2e0eeddd7be137e2494788e2dddb346f74c15c24..a76592f9b06a65be056fe0f6292bbb6cc2a2fb28 100644 (file)
--- a/src/msw/dib.cpp
+++ b/src/msw/dib.cpp
@@ -69,7 +69,7 @@ static inline WORD GetNumberOfColours(WORD bitsPerPixel)
 {
     // only 1, 4 and 8bpp bitmaps use palettes (well, they could be used with
     // 24bpp ones too but we don't support this as I think it's quite uncommon)
-    return bitsPerPixel <= 8 ? 1 << bitsPerPixel : 0;
+    return (WORD)(bitsPerPixel <= 8 ? 1 << bitsPerPixel : 0);
 }
 
 // wrapper around ::GetObject() for DIB sections
@@ -118,7 +118,7 @@ bool wxDIB::Create(int width, int height, int depth)
     info->bmiHeader.biHeight = height;
 
     info->bmiHeader.biPlanes = 1;
-    info->bmiHeader.biBitCount = depth;
+    info->bmiHeader.biBitCount = (WORD)depth;
     info->bmiHeader.biSizeImage = GetLineSize(width, depth)*height;
 
     m_handle = ::CreateDIBSection
@@ -151,10 +151,18 @@ bool wxDIB::Create(const wxBitmap& bmp)
 {
     wxCHECK_MSG( bmp.Ok(), false, _T("wxDIB::Create(): invalid bitmap") );
 
+    if ( !Create(GetHbitmapOf(bmp)) )
+        return false;
+
+    m_hasAlpha = bmp.HasAlpha();
+
+    return true;
+}
+
+bool wxDIB::Create(HBITMAP hbmp)
+{
     // this bitmap could already be a DIB section in which case we don't need
     // to convert it to DIB
-    HBITMAP hbmp = GetHbitmapOf(bmp);
-
     DIBSECTION ds;
     if ( GetDIBSection(hbmp, &ds) )
     {
@@ -172,18 +180,23 @@ bool wxDIB::Create(const wxBitmap& bmp)
     }
     else // no, it's a DDB -- convert it to DIB
     {
-        const int w = bmp.GetWidth();
-        const int h = bmp.GetHeight();
-        int d = bmp.GetDepth();
+        // prepare all the info we need
+        BITMAP bm;
+        if ( !::GetObject(hbmp, sizeof(bm), &bm) )
+        {
+            wxLogLastError(wxT("GetObject(bitmap)"));
+
+            return false;
+        }
+
+        int d = bm.bmBitsPixel;
         if ( d <= 0 )
             d = wxDisplayDepth();
 
-        if ( !Create(w, h, d) || !CopyFromDDB(hbmp) )
+        if ( !Create(bm.bmWidth, bm.bmHeight, d) || !CopyFromDDB(hbmp) )
             return false;
     }
 
-    m_hasAlpha = bmp.HasAlpha();
-
     return true;
 }
 
@@ -590,7 +603,7 @@ wxPalette *wxDIB::CreatePalette() const
 
     // initialize the palette header
     pPalette->palVersion = 0x300;  // magic number, not in docs but works
-    pPalette->palNumEntries = biClrUsed;
+    pPalette->palNumEntries = (WORD)biClrUsed;
 
     // and the colour table (it starts right after the end of the header)
     const RGBQUAD *pRGB = (RGBQUAD *)((char *)&ds.dsBmih + ds.dsBmih.biSize);
@@ -654,17 +667,30 @@ bool wxDIB::Create(const wxImage& image)
     {
         // copy one DIB line
         unsigned char *dst = dstLineStart;
-        for ( int x = 0; x < w; x++ )
+        if ( alpha )
         {
-            // also, the order of RGB is inversed for DIBs
-            *dst++ = src[2];
-            *dst++ = src[1];
-            *dst++ = src[0];
-
-            src += 3;
-
-            if ( alpha )
-                *dst++ = *alpha++;
+            for ( int x = 0; x < w; x++ )
+            {
+                // RGB order is reversed, and we need to premultiply
+                // all channels by alpha value for use with ::AlphaBlend.
+                const unsigned char a = *alpha++;
+                *dst++ = (unsigned char)((src[2] * a + 127) / 255);
+                *dst++ = (unsigned char)((src[1] * a + 127) / 255);
+                *dst++ = (unsigned char)((src[0] * a + 127) / 255);
+                *dst++ = a;
+                src += 3;
+            }
+        }
+        else // no alpha channel
+        {
+            for ( int x = 0; x < w; x++ )
+            {
+                // RGB order is reversed.
+                *dst++ = src[2];
+                *dst++ = src[1];
+                *dst++ = src[0];
+                src += 3;
+            }
         }
 
         // pass to the previous line in the image