Re: [Image-SIG] I'm confused by alpha blending.

Thu, 30 Mar 2006 13:28:02 -0800

I found the problem, thanks to the code you posted.  My destination image was "RGBA", and I was viewing it in a web browser.  Most of the image had an opaque alpha channel, but where I had drawn the drop shadows, it had the shadow's alpha values, so the white of the browser was showing through.  This isn't the most intuitive way for alpha drawing to work.  I guess I could see it both ways: if the destination is opaque, it should stay opaque, or drawing pixels onto a destination takes all the values from the source.

In any case, changing my destination image from RGBA to RGB solved the problem.

Thanks.

--Ned.

Fredrik Lundh wrote: 
are you 100% sure that the source pixels are black ?
    

a quick way to find out is to do

    print shadow.convert("RGB").getcolors()

</F>



_______________________________________________
Image-SIG maillist  -  [email protected]
http://mail.python.org/mailman/listinfo/image-sig



  

-- 
Ned Batchelder, http://nedbatchelder.com

_______________________________________________
Image-SIG maillist  -  [email protected]
http://mail.python.org/mailman/listinfo/image-sig

Reply via email to