Draw scaled images using CImageList

Question

If you have images stored in a CImageList, is there an easy way to render them (with proper transparency) scaled to fit a given target rectangle? CImageList::DrawEx takes size information but I don't believe it does scaling, only cropping?

Answer 1

I guess you could render them to an offscreen bitmap, then StretchBlt() them to either your device or another offscreen bitmap, letting StretchBlt() do the scaling... Getting the transparency to carry over correctly will require some fiddling though, depending on your circumstances you may need to use AlphaBlend() instead.

My opinion is that most of the Win32 image handling code, and therefore by extension their MFC equivalents, like CImageList, CIcon, CImage, CBitmap, ... are inadequate for today's graphics needs. Especially handling per-pixel transparency hardly ever works consistently. I usually store my images in a CImage and use ::AlphaBlend() everywhere to get them to DC, or I use GetDIBits()/SetDIBits() and directly manipulate the RGBA entries (not very practical for doing scaling and similar operations, I admit). On the other hand I understand what it's like having to maintain code that uses these things already and wanting to update them to give them a bit of a modern look...