[Closed] Checking a bitmap's alpha value

Mar 19, 2011 7:36 am

I want to loop thru a bitmap’s values until I come across the first instance of a non 0 alpha value.
How would I go about doing this, say for example in this context:

local myPSDlayer = bitmapLayerManager.LoadLayer aPSDfile 1 true

Something like:

for thePixels in myPSDlayer.pixelData do 
   	if thePixel.value != 0 then print "value>0"

Thanks!

3 Replies

lo1

Mar 19, 2011 7:36 am

you need to iterate over the pixels row by row using getpixels method. Get a row each time then iterate over each pixel of that row and check its .alpha property.

Panayot

Mar 19, 2011 7:36 am

If the case is just to test wheter the bitmap has alpha then this will save your time:

<bitmap>.[b]hasAlpha[/b]

TheGrak

Mar 19, 2011 7:36 am

@Lo – thanks! thats what i needed.
@Panayot – i have to check each pixels value, but that’s a handy code snippet.

  Here is what I ended up using:

--iterate over the pixels row by row using getpixels method. 
 for g = 0 to myBitmapHeight by 1 do --for the height of the bitmap
 (
      	local myPixelRow = getPixels myFullframebitmap [0,g] myBitmapWidth --get a row of pixels	
      	for j = 1 to myPixelRow.count do --for every row of pixels
      	(
      		if myPixelRow[j] != (color 0 0 0 0) then --if the pixel isn't completely transparent
      		(format "Opaque found at: [%,%]" g j)
      	 )
 )