PixMap and AlphaChannel

BlitzMax Forums/BlitzMax Beginners Area/PixMap and AlphaChannel

GregBUG (Posted 2007) [#1]

Hi Guys!! i need to "scan" a pixmap and detect if a pixel is "on" or off i use ReadPixel(MyPixMap,x, y) that return RGBA integer ... now the problem is that how can i detect if a pixel is on (colored) or off (trasparent)? many thanks!

tonyg (Posted 2007) [#2]

Won't it have values between 0-255 to show how much alpha is on each pixel? E.g. 0 = Full Alpha, >0 and < 255 = 'some' alpha, 255 = No alpha? Graphics 640 , 480 Local image:TPixmap = LoadPixmap("maxsmall.png") For Local x = 0 To pixmapwidth(image)-1 For Local y=0 To pixmapheight(image)-1 torgb(ReadPixel(image,x,y)) Next Next Function torgb(argb:Int) Local a:Int =(argb Shr 24) '& $ff Local r:Int =(argb Shr 16) & $ff Local g:Int =(argb Shr 8) & $ff Local b:Int = argb & $ff Print ("a: " + a + " r: " + r + " g: " + g + " b: " + b) Print End Function The pixmap is small (10*10) in this case. <edited> to make clearer but not sure if I have.

GregBUG (Posted 2007) [#3]

tonyg thanks!!!