Re: [boost] [gil] IMC4 Pixel format

Subject: Re: [boost] [gil] IMC4 Pixel format
From: Harg Tholan (hargtholan_at_[hidden])
Date: 2013-03-14 11:43:43

Thanks Chris for your prompt response.

I can certainly create the YUV color space first, basing myself on those
examples from the toolbox.
Once that it is done, we are ready to define the pixel formats afore
mentioned... at least for the IMC4.

If you want to take a look already,
here<http://www.fourcc.org/images/imc2.gif>you have an example of how
an image with a sub-sampled pixel format would
look like in memory. The core idea is that different channels have
different resolution! he idea is that the value of the channel 'U' is the
same for the pixels @(0, 0) , @(0, 1), @(1, 0), @(1, 1). Same applies to
the value of the channel 'V', but for the channel 'Y', they can hold
different values.

So iterating through pixels, we have to iterate through channels at
different 'speed' for they don't have the same resolution.

Thanks a lot Chris for your valuable help!
H4rg

2013/3/14 Christian Henning <chhenning_at_[hidden]>

> Hi,
>
> thanks for you interest in boost::gil!
>
> On Thu, Mar 14, 2013 at 10:48 AM, Harg Tholan <hargtholan_at_[hidden]>
> wrote:
> > Hey,
> >
> > I've been trying to find a definition for the
> > IMC4<http://www.fourcc.org/yuv.php#IMC4>pixel format for GIL with no
> > success, not even anything similar (planar
> > pixel formats in which some of the channels are sub-sampled).
>
> There are some color spaces in the toolbox, like xyz, lab, hsl, hsv,
> etc. Not sure if any of those can help you out. The toolbox has been
> added to boost trunk and should be released either with the next
> release or the following one.
>
> Could you give me some insight in how a yuv pixel could be defined?
> Like what are the bit sizes for each channel, for instance.
>
> >
> > I've spent many hours already trying to figure out how could I create
> such
> > pixel format, and I am totally lost...
>
> I'm sorry to hear that. I'm here to help but I have to concede that
> I'm not an expert in your field. So it could mutually benefiting. ;-)
>
> >
> > The question is how can I specify that a pixel format is planar, and
> planes
> > have different sizes due to sub-sampling!....I guess I'll have to
> override
> > some operator[] operator++, operator-- Or to make a specialization of
> some
> > classes.
> >
> > But how and where? planar_pixel_iterator? channel_iterator?
> > I need some aid! please!
>
> Let's start at the beginning, like defining the pixel time. I can help
> and spell your code into gil code if necessary.
>
> Regards,
> Christian
>
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