Re: Reading RGBA pixel values from image on disk
Re: Reading RGBA pixel values from image on disk
- Subject: Re: Reading RGBA pixel values from image on disk
- From: Kyle Sluder <email@hidden>
- Date: Thu, 10 Mar 2011 11:00:43 -0800
On Thu, Mar 10, 2011 at 10:47 AM, Leonardo <email@hidden> wrote:
> I forgot: if I save the TIF from Photoshop marking the check-box "Save
> Transparency", on my App I can quite read the alpha channel, and the RGB
> values are not pre-multiplied. That's fine.
> Anyway, without the "Save Transparency", on my App I get the RGB values
> pre-multiplied and the alpha values are all 1.0, so I can't calculate the
> original RGB values. The weird point is that if I re-open this TIF file with
> Photoshop, the half-a-transparent pixels are well visible. So the alpha
> information has been properly stored within the TIF file, somewhere. I would
> like to know where.
Probably in a custom Photoshop chunk.
TIFF isn't a very well-standardized format. Photoshop sticks a ton of
stuff in custom chunks.
You should probably consider giving up on TIFF and moving to PNG.
--Kyle Sluder
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