Re: [Boost-users] [GIL] gray pixel iterator in generic algorithm

Subject: Re: [Boost-users] [GIL] gray pixel iterator in generic algorithm
From: Robert Lupton the Good (rhl_at_[hidden])
Date: 2010-12-23 09:22:08

Dear Lubomir,

This must be quite common (I have the same problem, wanting unscaled values, in astronomical images).  It was quite a lot of work to implement all the types I needed (short, int, float, double) as unscaled types that properly convert (i.e. don't,  1234 -> 1234.0).  I can share the code if you like, but I wrote it long ago when I was learning both gil and C++.  Should this be easy?

It would be really nice if gil supported unscaled types out of the box.

                                        R

> I'm performing quantitative analysis with a physically significant  
> gray scale.  So I don't expect to do any color conversion.
> 
> On Dec 22, 2010, at 2:23 PM, Lubomir Bourdev wrote:
> 
>> Hi Curtis,
>> 
>> GIL's default float type is not "float" but a special float wrapper  
>> to ensure that the range is 0..1
>> The built-in float has a range from -infinity to infinity and that  
>> does not work well when converting a value from another channel type.
>> If you want an image with a standard float you can create it like  
>> this (untested)
>> 
>> typedef pixel<float,gray_layout_t> gray_float_pixel_t;
>> typedef image<gray_float_pixel_t,false> gray_float_image_t;
>> typedef gray_float_image_t::view_t gray_float_view_t;