Pixmap paste with mask

This code has been declared by its author to be Public Domain code.

Pixmap paste with mask by tonyg

2006

The supplied Pixmap.paste method will use memcopy to copy
all the pixels from source to target. This means that pixels normally omitted using the mask colour are also copied. This function (which could do with a tidy up) will copy pixels from source to target omitting pixels whose colour matches the mask.

Graphics 640,480
image1:TImage=LoadImage("max.png")
image2:TImage=LoadImage("light.png")
While Not KeyHit(key_escape)
	Cls
	If MouseHit(1)
		argb:Int=intcolor(image2.mask_r,image2.mask_g,image2.mask_b)
		image1:TImage=drawbuffer(image1,image2,0,0,argb)
	EndIf
	DrawImage image1,0,0
	Flip
Wend
WaitKey()
Function drawbuffer:TImage(imagea:TImage,imageb:TImage,x:Int,y:Int,argb:Int)
  If x + ImageWidth(imageb) > ImageWidth(imagea) Or y + ImageHeight(imageb) > ImageHeight(imagea) RuntimeError("Imagea to big to fit in imageb")
'  start_func=MilliSecs()
  mypixmap2:TPixmap=LockImage(imageb)
  UnlockImage(imageb)
  mypixmap1:TPixmap=LockImage(imagea)
  Local mypixelptr2:Int Ptr = Int Ptr(mypixmap2.pixelptr(0,0))
  Local mypixelptr2backup:Int Ptr = mypixelptr2
  Local mypixelptr1:Int Ptr = Int Ptr(mypixmap1.pixelptr(x,y))
  Local mypixelptr1backup:Int Ptr = mypixelptr1
  For my_x=0 To ((mypixmap2.width)*(mypixmap2.height))
     If mypixelptr2[0] <> argb 
         If mypixelptr2[0] <> 0 mypixelptr1[0]=mypixelptr2[0]
 '             If mypixelptr2[0] <> 16777215 mypixelptr1[0]=mypixelptr2[0]
    EndIf
     mypixelptr1:+1
     mypixelptr2:+1
     If mypixelptr2 = mypixelptr2backup+(mypixmap2.pitch Shr 2)
         mypixelptr1 = mypixelptr1backup+(mypixmap1.pitch Shr 2)
         mypixelptr1backup=mypixelptr1
         mypixelptr2backup=mypixelptr2
     EndIf
  Next
  Return LoadImage(mypixmap1)
'  end_func=MilliSecs()
End Function
Function IntColor(R,G,B,A=255)
'returns argb value from red, green, blue.
     Return A Shl 24 | R Shl 16 | G Shl 8 | B Shl 0
End Function

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