I'm sure you thought of it but for now could you use RGBA? Probably not, but what would an alignment of 4 refer to? Is it size in bytes or channels? Could you describe a use case? Regards, Christian On Thu, Dec 26, 2013 at 10:21 AM, TONGARI J wrote:

2013/12/26 TONGARI J

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Hi there,

The current gil::pixel design has a deficiency that you can't specify the align of pixel, for example, you can't have an RGBX pixel in GIL where X is padding.

An alternative is to introduce a dummy channel for X, but that doesn't seem to be a good idea as we don't want to mess up the color space.

So, maybe it'd be better to extend the current design, say, pixel, to something like pixel.

Then we can specify RGBX as pixel, or XRGB as pixel where minus means left justify.

Sorry, I mean RGBX as pixel; XRGB as pixel, apparently I'm confused by myself :p

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Ideas?

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Could you describe a use case?

I have to work with something like RGBQUAD which's layout is BGRX:

http://msdn.microsoft.com/en-us/library/windows/desktop/dd162938(v=vs.85).as...

QQ, the rgbReserved represents the alignment? Christian

2013/12/28 TONGARI J

2013/12/28 Christian Henning

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Could you describe a use case?

I have to work with something like RGBQUAD which's layout is BGRX:

http://msdn.microsoft.com/en-us/library/windows/desktop/dd162938(v=vs.85).as...

QQ, the rgbReserved represents the alignment?

At least it requires 4 bytes by that structure. Also note that Quartz 2D also has padded RGB: http://tinyurl.com/kdawwkl So I think GIL being a generic library is reasonable to fill such a requirement.

Now I have my pixel defined as:

template class pixel;

So RGBX becomes pixel.

I thought I could plug my custom pixel into GIL elegantly, but I was wrong :( Is GIL not for extending!? The design somewhat prevents the user from customizing their pixels. For example, gil::at_c for each existed pixel is defined by overloading, that's a big problem for extension, the custom types after come cannot just overload 'at_c' to work with GIL, since those color_base_algorithm can only see those 'at_c' which are already defined before, not after. As the result, you see the huge "gil_concept.hpp" with lots of forward declaration :/ Can this be improved, like what Fusion does? Thanks,

2013/12/29 Christian Henning

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For example, gil::at_c for each existed pixel is defined by overloading, that's a big problem for extension, the custom types after come cannot just overload 'at_c' to work with GIL, since those color_base_algorithm can only see those 'at_c' which are already defined before, not after. As the result, you see the huge "gil_concept.hpp" with lots of forward declaration :/

Can this be improved, like what Fusion does?

Would you provide some code to play around with?

May I introduce you to the mechanism Fusion used: https://github.com/boostorg/fusion/blob/master/include/boost/fusion/sequence... then the user would specialize boost::fusion::extension::at_impl for their own type. HTH

On Fri, Dec 27, 2013 at 1:05 PM, TONGARI J wrote:

2013/12/28 Christian Henning

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Could you describe a use case?

I have to work with something like RGBQUAD which's layout is BGRX:

http://msdn.microsoft.com/en-us/library/windows/desktop/dd162938(v=vs.85).as...

...

QQ, the rgbReserved represents the alignment?

At least it requires 4 bytes by that structure. Also note that Quartz 2D also has padded RGB: http://tinyurl.com/kdawwkl So I think GIL being a generic library is reasonable to fill such a requirement.

Now I have my pixel defined as:

template class pixel;

So RGBX becomes pixel.

So, pixel in memory looks like ( a letter representing a byte ): rgbxrgbxrgbx... pixel would be rgbxxrgbxxrgbxx... Is that correct? Do you already have some code which could be added to GIL? I would be willing to incorporate it and write tests and update documentation. I have added your proposal to my gil todo list but I'm afraid I don't have time right now. Christian