How to: 8-bit bitmap masks for soft edge creation

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Mon, 2005-08-22 12:40
sono
Joined: 2005-02-22
 Forum posts: 12
Hello!

According to Nokia's documentation, bitmap items can have two different
types of masks: a 1-bit masks (hard masks) and an 8-bit masks (soft masks). An 8-bit mask is a greyscale image and allows creation of soft edges (anti-aliasing), and semi-transparency.

Until now I have only used 1-bit greyscale (black) masks, that I painted in
the simplier way, by using BitBltMasked, this way:

Code:
CFbsBitmap* iBmp = new(ELeave)CFbsBitmap();
CFbsBitmap* iBmpMask = new(ELeave)CFbsBitmap();
User::LeaveIfError(iBmp->Load(pathToMbm, bmpindex));    //path to mbm and index to the bitmap
User::LeaveIfError(iBmpMask->Load(pathToMbm, maskindex));    //path to mbm and index to the 1-bit mask
//... creation of the screen gc
iOffGc->SetBrushStyle(CGraphicsContext::ENullBrush);
iOffGc->BitBltMasked(pointToDraw, iBmp, TRect(TPoint(0, 0), iBmp->SizeInPixels()), iBmpMask, ETrue);

How can I use the way to mask bitmaps with 8-bit greyscale masks too? Some of my "rounded-shape" bitmaps look notched using the 1-bit mask only (some of the light-coloured pixels are lost from the mask), and it's rather ugly (as seen in the below image).



I used them often in my grid-like menus in the way described in the picture below (bitblt with mask and coloured or white background). I could use rectangular bitmaps and alpha-blending on the non-white pixels (windows-style: icons view in windows explorer look) for the highlited ones, but it's a resource-eating process (and I have dozens of bitmaps in the same screen).

Can anybody please help me with a clue (advices, ways-to-do, documentation links) or a fragment of source code related to this subject?

Thanks in advance!
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