Function GetSubImageWithAlpha

libraries/lib-theme/ImageManipulation.cpp:354–414

Gets a rectangle from within another image, INCLUDING the alpha channel \bug in wxWidgets, wxImage::GetSubImage should do this itself.

/// Gets a rectangle from within another image, INCLUDING the alpha channel
/// \bug in wxWidgets, wxImage::GetSubImage should do this itself.
wxImage GetSubImageWithAlpha( const wxImage & Src,  const wxRect &rect )
{
   //First part of this code is lifted from wxImage::GetSubImage() source code.
   wxImage image;

   wxCHECK_MSG( Src.Ok(), image, wxT("invalid image") );

   wxCHECK_MSG( (rect.GetLeft()>=0) && (rect.GetTop()>=0) && (
      rect.GetRight()<=Src.GetWidth()) && (rect.GetBottom()<=Src.GetHeight()),
      image, wxT("invalid subimage size") );

   int subwidth=rect.GetWidth();
   const int subheight=rect.GetHeight();

   image.Create( subwidth, subheight, false );

   unsigned char *subdata = image.GetData(), *data=Src.GetData();

   wxCHECK_MSG( subdata, image, wxT("unable to create image") );

   // JKC: Quick hack - don't deal with masks - need to understand macro M_IMGDATA first.
//   if (Src.M_IMGDATA->m_hasMask)
//      image.SetMaskColour( Src.M_IMGDATA->m_maskRed, Src.M_IMGDATA->m_maskGreen, Src.M_IMGDATA->m_maskBlue );

   int subleft=3*rect.GetLeft();
   int width=3*Src.GetWidth();
   subwidth*=3;

   data+=rect.GetTop()*width+subleft;

   for (long j = 0; j < subheight; ++j)
   {
      memcpy( subdata, data, subwidth);
      subdata+=subwidth;
      data+=width;
   }

   image.InitAlpha();
   if( !Src.HasAlpha() )
      return image;
   // OK, so we've copied the RGB data.
   // Now do the Alpha channel.
   //wxASSERT( Src.HasAlpha() );

   subleft/=3;
   width/=3;
   subwidth/=3;

   data =Src.GetAlpha();
   subdata =image.GetAlpha();

   data+=rect.GetTop()*width+subleft;

   for (long j = 0; j < subheight; ++j)
   {
      memcpy( subdata, data, subwidth);
      subdata+=subwidth;
      data+=width;