[ITK] [ITK-users] read palette image as scalar image + palette, instead of RGB image

[Dženan Zukić]

Hi Yann,

this would be a good addition to ITK, please submit a patch to Gerrit. I
think it is more logical to keep it in itkBPMImageIO, itkTiffImageIO, and
itkPNGImageIO instead of adding it to itkImageFileReader because not all
formats support color palette. Whoever needs this functionality could
access it through ImageIO.

Regards,
Dženan

On Wed, Jan 25, 2017 at 8:52 AM, Lowekamp, Bradley (NIH/NLM/LHC) [C] <
blowekamp at mail.nih.gov> wrote:

> This sounds like a great addition.
>
> I would not implement the method in ImageFileReader yet. It should be
> easily enough to add it later.
>
> Are you planning of exposing the palette after loading? The
> MetaDataDictionary could be used for this. But we don’t have any palette
> data structure or established conventions yet.
>
> I look forward to seeing your patch.
> Brad
>
> On Jan 24, 2017, at 10:06 AM, asertyuio via Insight-users <
> insight-users at itk.org> wrote:
>
> Hi Dženan,
>
> Thanks, you gave me the right direction!
>
> I have adapted itkBPMImageIO, itkTiffImageIO, and itkPNGImageIO so that
> the user have the choice to expand the color palette or not, and retrive a
> vector of RGBPixel corresponding to this palette. I will try to submit
> these changes to gerrit.
>
> I'm not quite sure whether I should push a bit more so that this choice
> could be set directly in itkImageReader. Do you have any advice ?
>
> Thanks for your answer,
>
> Yann
>
> Le 16/01/2017 à 15:50, Dženan Zukić a écrit :
>
> Hi Yann,
>
> the relevant part of code for PNG format is in itkPNGImageIO.cxx,
> approximately lines 365-395 (link
> <https://github.com/InsightSoftwareConsortium/ITK/blob/578d3660e71022680d3abf313ad8b84ce2a7dd66/Modules/IO/PNG/src/itkPNGImageIO.cxx#L365-L393>).
> You will need to modify that. If you modify it in a way so it can be useful
> for others, please submit your patch to code review
> <https://itk.org/Wiki/ITK/Git/Develop>.
>
> To get access to the specialized functions of the PNG reader, you would
> instantiate it directly:
> itk::PNGImageIO::Pointer imageIO = ...
> std::vector<RGBPixel> colorTable = imageIO->GetColorTable(); //call a
> function you added to PNG reader
>
> Hope this helps,
> Dženan
>
> On Sun, Jan 15, 2017 at 11:07 AM, asertyuio via Insight-users <
> <insight-users at itk.org>insight-users at itk.org> wrote:
>
>> Hi all,
>>
>> I want to read a palette image as a scalar image with its indexes + a
>> vector of RGB, corresponding to the image palette. The format of the image
>> is TIFF, but can be png or gif as well.
>>
>> When I'm reading such palette image, the itk::ImageIOBase, as
>> implemented here
>> <https://itk.org/ITKExamples/src/IO/ImageBase/ReadUnknownImageType/Documentation.html>,
>> tels me that the image has a RGB pixel type.
>>
>> itk::ImageIOBase::Pointer imageIO =
>>     itk::ImageIOFactory::CreateImageIO(
>>         fileName, itk::ImageIOFactory::ReadMode);
>>
>> Is it possible to know, *through ITK*, whether the image is actually a
>> palette image, *i.e.* scalar image along with a color palette, and read
>> this image as a scalar image + palette ? I need have access to the index,
>> as stored in the file as well as the color palette used in the file.
>>
>> For now, my only solution is to use freeImagePlus to identify and read
>> this type of image. I haven't found any function in the class ImageIOBase
>> that could relate to that.
>>
>> Any help would be appreciated, thanks a lot ! Yann
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