Re: [Boost-users] [GIL] Problem trying to use scoped_channel_value with copy_and_convert_pixels

Subject: Re: [Boost-users] [GIL] Problem trying to use scoped_channel_value with copy_and_convert_pixels
From: Nate Crookston (nathan.crookston_at_[hidden])
Date: 2015-01-12 14:04:45

Hi Gabriel,

I've successfully done what you're trying to do I think.  I wrote about
some problems in the following thread:
https://groups.google.com/forum/#!topic/boost-list/4CqibxPFdUw.  In short,
I had to specialize a few other metafunctions.  I think we should add a
scoped_integral_channel_value type which has appropriate specializations
for people trying to do what you're doing.

I had to make the following change to compile with c++11 clang:

*diff --git a/include/boost/gil/channel_algorithm.hpp
b/include/boost/gil/channel_algorithm.hpp*

*index 1361219..1799470 100644*

*--- a/include/boost/gil/channel_algorithm.hpp*

*+++ b/include/boost/gil/channel_algorithm.hpp*

@@ -51,7 +51,7 @@ template <typename SrcChannelV, typename DstChannelV,
bool SrcLessThanDst, bool

 template <typename UnsignedIntegralChannel>

-struct unsigned_integral_max_value : public
mpl::integral_c<UnsignedIntegralChannel,-1> {};

+struct unsigned_integral_max_value : public
mpl::integral_c<UnsignedIntegralChannel,(1<<sizeof(Un

 template <>

 struct unsigned_integral_max_value<uint8_t> : public
mpl::integral_c<uint32_t,0xFF> {};

Then I added a couple specializations in your code:

#include <boost/gil/gil_all.hpp>

#include <cstdint>

using namespace std;

using namespace boost::gil;

namespace detail

{

    struct bits14_min { static std::uint16_t apply() { return 0;} };

    struct bits14_max { static std::uint16_t apply() { return 0x3FF;} };

}

typedef scoped_channel_value <std::uint16_t, ::detail::bits14_min,
::detail::bits14_max> bits14_t;

namespace boost { namespace gil { namespace detail {

  template <> struct unsigned_integral_max_value<bits14_t> : public
mpl::integral_c<uint32_t,0x3FF> {};

  template <> struct unsigned_integral_num_bits<bits14_t> : public
mpl::int_<14> {};

}}}

typedef pixel<bits14_t, gray_layout_t> Pixel1;

typedef image<Pixel1> Frame1;

int main()

{

  bits14_t x = channel_traits<bits14_t>::max_value();

  assert(x == 0x3ff);

  bits16 y = channel_convert<bits16>(x);

  assert(y == 0xffff);

  Frame1 image(

      Frame1::point_t(100, 100),

      Frame1::value_type((1 << 14)-1),

      0);

  gray16_image_t image2(image.dimensions());

  Frame1::view_t view1(view(image));

  gray16_image_t::view_t view2(view(image2));

  copy_and_convert_pixels(view1, view2);

  return 0;

}

On Thu, Jan 8, 2015 at 4:13 PM, Gabriel Marcano <gabemarcano_at_[hidden]>
wrote:

> I have been experimenting with Boost.GIL, and I have run into something
> that I'm not sure if it's a problem on my end or with Boost.GIL. In
> essence, I'm trying to make a grayscale image with channels limited to
> 14 bits. I am using scoped_channel_value to do this. The problem
> happens when I try to convert the 14 bit image to a 16 bit grayscale
> image I get compilation errors. I am including the code I am using
> below:
>
> //START CODE
>
>     #include <boost/gil/gil_all.hpp>
>     #include <cstdint>
>
>     using namespace std;
>     using namespace boost::gil;
>
>     namespace detail
>     {
>         struct bits14_min { static std::uint16_t apply() { return 0;} };
>         struct bits14_max
>            { static std::uint16_t apply() { return 0x3FF;} };
>     }
>
>     typedef scoped_channel_value
>         <std::uint16_t,
>             ::detail::bits14_min, ::detail::bits14_max> bits14_t;
>
>     typedef pixel<bits14_t, gray_layout_t> Pixel1;
>     typedef image<Pixel1> Frame1;
>
>     int main()
>     {
>         Frame1 image(
>             Frame1::point_t(100, 100),
>             Frame1::value_type((1 << 14)-1),
>             0);
>
>         gray16_image_t image2(image.dimensions());
>
>         Frame1::view_t view1(view(image));
>         gray16_image_t::view_t view2(view(image2));
>
>         copy_and_convert_pixels(view1, view2);
>
>         return 0;
>     }
>
> //END CODE
>
> The interesting thing is that the program compiles if change
>     typedef scoped_channel_value
>         <std::uint16_t,
>             ::detail::bits14_min, ::detail::bits14_max> bits14_t;
> to
>     typedef scoped_channel_value
>         <float,
>             ::detail::bits14_min, ::detail::bits14_max> bits14_t;
>
> I think the relevant error in the log is this:
>     /usr/include/boost/gil/channel_algorithm.hpp:54:8: error:
>         ‘struct boost::gil::scoped_channel_value<short unsigned
>         int, detail::bits14_min, detail::bits14_max>’ is not a
>         valid type for a template non-type parameter
>          struct unsigned_integral_max_value : public
>              mpl::integral_c<UnsignedIntegralChannel,-1> {};
>
> I am attaching the full compile log to this email. Thank you for any
> help with this matter!
>
> Sincerely,
>
> Gabriel E. Marcano
>
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