Re: [Boost-users] [Gil] TIFF file with mixed 8/16 bit channel depths

Subject: Re: [Boost-users] [Gil] TIFF file with mixed 8/16 bit channel depths
From: Christian Henning (chhenning_at_[hidden])
Date: 2011-11-03 10:56:16

Hi Corinna,

could you tell me the image type you're passing into read_image?

Regards,
Christian

On Thu, Nov 3, 2011 at 10:53 AM, Corinna Kinchin <crin_at_[hidden]> wrote:
> Hello,
>
> I'm using
>
>        boost::gil::read_image(in, img, tiff_tag());
>
> as part of a process to extract raw image data from a TIFF file,
> and it works beautifully for cmyka TIFF files containing either
> 5 x 8-bit channels, or 5 x 16-bit channels. But it seems using
> this technique mangles image data contained in a (photoshop
> generated) TIFF file which contains CMYK channels with both 8
> and 16 bit depths (mixed).
>
> Here is an extract from the ImageMagick 'identify -verbose'
> output on such a file:
>
>  Depth: 8/16-bit
>
>  Channel depth:
>  cyan: 16-bit
>  magenta: 16-bit
>  yellow: 16-bit
>  black: 8-bit
>  alpha: 8-bit
>
> It seems that read_image treats the TIFF file as if it contains
> 5 x 8-bit channels (the TIFFTAG_BITSPERSAMPLE property and
> hence the _bits_per_sample info value for the TIFF file is set to 8),
> so the CMY channel image data isn't read in correctly ... at least
> that's my best guess.
>
> Does anyone out there know whether boost::gil can be made to support
> 8/16bit TIFF files - eg if there's an extension (or hack ;) which
> could do the trick? Or any other options (eg other libraries) which
> could be worth investigation?
>
> Many thanks for reading this far, and if you have any remotely relevent
> ideas it would be great to hear them ...
>
> All the best,
>
> Corinna ...
>
>  Corinna Kinchin                 email: ckinchin_at_[hidden]
>  Datazone Ltd.                   Tel:   [phone]
>  Palm Gate, Greenane,            Fax:   [phone]
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>
>  Datazone - makers of `Miramo', the automated publishing tool
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