void ImposterCapture::_separateAlpha( GBitmap *imposterOut )
{
PROFILE_START(TSShapeInstance_snapshot_sb_separate);
// TODO: Remove all this when we get rid of the 'render on black/white'.
// now separate the color and alpha channels
GBitmap *bmp = new GBitmap;
bmp->allocateBitmap(mDim, mDim, false, GFXFormatR8G8B8A8);
U8 * wbmp = (U8*)mWhiteBmp->getBits(0);
U8 * bbmp = (U8*)mBlackBmp->getBits(0);
U8 * dst = (U8*)bmp->getBits(0);
const U32 pixCount = mDim * mDim;
// simpler, probably faster...
for ( U32 i=0; i < pixCount; i++ )
{
// Shape on black background is alpha * color, shape on white
// background is alpha * color + (1-alpha) * 255 we want 255 *
// alpha, or 255 - (white - black).
//
// JMQ: or more verbosely:
// cB = alpha * color + (0 * (1 - alpha))
// cB = alpha * color
// cW = alpha * color + (255 * (1 - alpha))
// cW = cB + (255 * (1 - alpha))
// solving for alpha
// cW - cB = 255 * (1 - alpha)
// (cW - cB)/255 = (1 - alpha)
// alpha = 1 - (cW - cB)/255
// since we want alpha*255, multiply through by 255
// alpha * 255 = 255 - cW - cB
U32 alpha = 255 - (wbmp[i*3+0] - bbmp[i*3+0]);
alpha += 255 - (wbmp[i*3+1] - bbmp[i*3+1]);
alpha += 255 - (wbmp[i*3+2] - bbmp[i*3+2]);
if ( alpha != 0 )
{
F32 floatAlpha = ((F32)alpha)/(3.0f*255.0f);
dst[i*4+0] = (U8)(bbmp[i*3+0] / floatAlpha);
dst[i*4+1] = (U8)(bbmp[i*3+1] / floatAlpha);
dst[i*4+2] = (U8)(bbmp[i*3+2] / floatAlpha);
// Before we assign the alpha we "fizzle" the value
// if its greater than 84. This causes the imposter
// to dissolve instead of popping into view.
alpha /= 3;
dst[i*4+3] = (U8)alpha;
}
else
{
dst[i*4+0] = dst[i*4+1] = dst[i*4+2] = dst[i*4+3] = 0;
}
}
PROFILE_END(); // TSShapeInstance_snapshot_sb_separate
PROFILE_START(TSShapeInstance_snapshot_sb_filter);
// We now run a special kernel filter over the image that
// averages color into the transparent areas. This should
// in essence give us a border around the edges of the
// imposter silhouette which fixes the artifacts around the
// alpha test billboards.
U8* dst2 = (U8*)imposterOut->getBits(0);
_colorAverageFilter( mDim, dst, dst2 );
if ( 0 )
{
FileStream fs;
if ( fs.open( "./imposterout.png", Torque::FS::File::Write ) )
imposterOut->writeBitmap( "png", fs );
fs.close();
if ( fs.open( "./temp.png", Torque::FS::File::Write ) )
bmp->writeBitmap( "png", fs );
fs.close();
}
PROFILE_END(); // TSShapeInstance_snapshot_sb_filter
delete bmp;
}
