Code: Select all
Procedure DrawTransparentImage(DC, Bitmap, x, y, Width, Height, TransparentColor)
; First, create some DC's. These are our gateways To associated
; bitmaps in RAM
maskDC = CreateCompatibleDC_(DC)
tempDC = CreateCompatibleDC_(DC)
SourceDC = CreateCompatibleDC_(DC)
SelectObject_(SourceDC, Bitmap)
; Then, we need the bitmaps. Note that we create a monochrome
; bitmap here!
; This is a trick we use For creating a mask fast enough.
hMaskBmp = CreateBitmap_(Width, Height, 1, 1, 0)
hTempBmp = CreateCompatibleBitmap_(DC, Width, Height)
; Then we can assign the bitmaps to the DCs
;
hMaskBmp = SelectObject_(maskDC, hMaskBmp)
hTempBmp = SelectObject_(tempDC, hTempBmp)
; Now we can create a mask. First, we set the background color
; To the transparent color; then we copy the image into the
; monochrome bitmap.
; When we are done, we reset the background color of the
; original source.
TransparentColor= SetBkColor_(SourceDC, TransparentColor)
BitBlt_ (maskDC, 0, 0, Width, Height, SourceDC, 0, 0, #SRCCOPY)
SetBkColor_(SourceDC, TransparentColor)
; The first we do with the mask is To MergePaint it into the
; destination.
; This will punch a WHITE hole in the background exactly were
; we want the graphics To be painted in.
BitBlt_ (tempDC, 0, 0, Width, Height, maskDC, 0, 0, #SRCCOPY)
BitBlt_ (DC, x, y, Width, Height, tempDC, 0, 0, #MERGEPAINT)
; Now we delete the transparent part of our source image. To do
; this, we must invert the mask And MergePaint it into the
; source image. The transparent area will now appear as WHITE.
BitBlt_ (maskDC, 0, 0, Width, Height, maskDC, 0, 0, #NOTSRCCOPY)
BitBlt_ (tempDC, 0, 0, Width, Height, SourceDC, 0, 0, #SRCCOPY)
BitBlt_ (tempDC, 0, 0, Width, Height, maskDC, 0, 0, #MERGEPAINT)
; Both target And source are clean. All we have To do is To And
; them together!
BitBlt_ (DC, x, y, Width, Height, tempDC, 0, 0, #SRCAND)
; Now all we have To do is To clean up after us And free system
; resources..
DeleteObject_ (hMaskBmp)
DeleteObject_ (hTempBmp)
DeleteDC_ (maskDC)
DeleteDC_ (tempDC)
DeleteDC_ (SourceDC)
EndProcedure
