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: Leonardo <email@hidden>
- Date: Thu, 10 Mar 2011 18:25:18 +0100
- Thread-topic: Reading RGBA pixel values from image on disk
Hi Quincey,
if I re-open the same TIF file with Photoshop, I can quite see the
half-a-transparent pixels. So, it seems that the alpha information has been
properly saved within the TIF file. I would like to know how to manage a
file like this and retrieve the transparency (alpha) of those pixels.
I can send you this TIF file, if you agree. It's only 42KB.
Regards
-- Leonardo
> Da: Quincey Morris <email@hidden>
> Data: Thu, 10 Mar 2011 09:13:54 -0800
> A: Leonardo <email@hidden>
> Cc: <email@hidden>
> Oggetto: Re: Reading RGBA pixel values from image on disk
>
> On Mar 10, 2011, at 07:18, Leonardo wrote:
>
>> But if I save the same image with Photoshop as TIF, I get an "alpha
>> premultiplied" bitmap format and a bitsPerPixel = 24. But worst of all, all
>> the alpha values are 1.0, while some of them is for sure 0.5. So I can't
>> even calculate the original non multiplied RGB values.
>
> Well, what's your evidence that Photoshop didn't save the file as RGB (rather
> than RGBA or ARGB), since bitsPerPixel==24 suggests that it did?
>
>
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