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store bitmap data in premultiplied by alpha format in wxBitmap/wxDIB (patch 991172)

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29622 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2004-10-03 14:03:52 +00:00
parent 57c26f8210
commit e5d4ef7410
2 changed files with 33 additions and 49 deletions
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49
src/msw/bitmap.cpp
View File

@@ -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<wxBitmap, wxAlphaPixelFormat> 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 )

23
src/msw/dib.cpp
View File

@@ -667,17 +667,30 @@ bool wxDIB::Create(const wxImage& image)
{
// copy one DIB line
unsigned char *dst = dstLineStart;
if ( alpha )
{
for ( int x = 0; x < w; x++ )
{
// also, the order of RGB is inversed for DIBs
// 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;
if ( alpha )
*dst++ = *alpha++;
}
}
// pass to the previous line in the image