From: Vadim Zeitlin Date: Sun, 3 Oct 2004 14:03:52 +0000 (+0000) Subject: store bitmap data in premultiplied by alpha format in wxBitmap/wxDIB (patch 991172) X-Git-Url: https://git.saurik.com/wxWidgets.git/commitdiff_plain/e5d4ef7410d597bdf6d426ceedc656dbefd69e90 store bitmap data in premultiplied by alpha format in wxBitmap/wxDIB (patch 991172) git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29622 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775 --- diff --git a/src/msw/bitmap.cpp b/src/msw/bitmap.cpp index e666d7a8d5..b80b7989d9 100644 --- a/src/msw/bitmap.cpp +++ b/src/msw/bitmap.cpp @@ -1025,11 +1025,13 @@ wxBitmap wxBitmap::GetSubBitmap( const wxRect& rect) const (rect.y+rect.height <= GetHeight()), wxNullBitmap, wxT("Invalid bitmap or bitmap region") ); - wxBitmap ret( rect.width, rect.height ); + wxBitmap ret( rect.width, rect.height, GetDepth() ); wxASSERT_MSG( ret.Ok(), wxT("GetSubBitmap error") ); #ifndef __WXMICROWIN__ - // TODO: copy alpha channel data if any + // handle alpha channel, if any + if (HasAlpha()) + ret.UseAlpha(); // copy bitmap data MemoryHDC dcSrc, @@ -1223,7 +1225,11 @@ void *wxBitmap::GetRawData(wxPixelDataBase& data, int bpp) data.m_height = h; // remember that DIBs are stored in top to bottom order! - const LONG bytesPerRow = ds.dsBm.bmWidthBytes; + // (We can't just use ds.dsBm.bmWidthBytes here, because it isn't always a + // multiple of 2, as required by the documentation. So we use the official + // formula, which we already use elsewhere.) + const LONG bytesPerRow = + wxDIB::GetLineSize(ds.dsBm.bmWidth, ds.dsBm.bmBitsPixel); data.m_stride = -bytesPerRow; char *bits = (char *)ds.dsBm.bmBits; @@ -1244,12 +1250,7 @@ void wxBitmap::UngetRawData(wxPixelDataBase& dataBase) if ( !Ok() ) return; - // the cast is ugly but we can't do without it and without making this - // function template (and hence inline) unfortunately - typedef wxPixelData PixelData; - PixelData& data = (PixelData &)dataBase; - - if ( !data ) + if ( !&dataBase ) { // invalid data, don't crash -- but don't assert neither as we're // called automatically from wxPixelDataBase dtor and so there is no @@ -1257,36 +1258,6 @@ void wxBitmap::UngetRawData(wxPixelDataBase& dataBase) return; } - if ( GetBitmapData()->m_hasAlpha ) - { - // AlphaBlend() wants to have premultiplied source alpha but - // wxRawBitmap API uses normal, not premultiplied, colours, so adjust - // them here now - PixelData::Iterator p(data); - - const int w = data.GetWidth(); - const int h = data.GetHeight(); - - for ( int y = 0; y < h; y++ ) - { - PixelData::Iterator rowStart = p; - - for ( int x = 0; x < w; x++ ) - { - const unsigned alpha = p.Alpha(); - - p.Red() = (p.Red() * alpha + 127) / 255; - p.Blue() = (p.Blue() * alpha + 127) / 255; - p.Green() = (p.Green() * alpha + 127) / 255; - - ++p; - } - - p = rowStart; - p.OffsetY(data, 1); - } - } - // if we're a DDB we need to convert DIB back to DDB now to make the // changes made via raw bitmap access effective if ( !GetBitmapData()->m_isDIB ) diff --git a/src/msw/dib.cpp b/src/msw/dib.cpp index a7eebe54f2..285fd9142e 100644 --- a/src/msw/dib.cpp +++ b/src/msw/dib.cpp @@ -667,17 +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++ = (src[2] * a + 127) / 255; + *dst++ = (src[1] * a + 127) / 255; + *dst++ = (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