GTKD Cairo get pixel color

[Basile B. via Digitalmars-d-learn]

On Friday, 1 January 2016 at 22:00:04 UTC, TheDGuy wrote:
> On Friday, 1 January 2016 at 19:32:40 UTC, Basile B. wrote:
>> On Wednesday, 30 December 2015 at 23:20:23 UTC, Basile B. 
>> wrote:
>>> On Wednesday, 30 December 2015 at 20:44:44 UTC, TheDGuy wrote:
>>>> Hello,
>>>>
>>>> is there any way to get the pixel color of a single pixel by 
>>>> x and y coordinates of a context?
>>>
>>> render to a png back buffer.
>>>
>>> see cairo_image_surface_create_for_data
>>>
>>> then you'll be able to access the data and, at the same time, 
>>> to blit your buffer to screen.
>>
>>
>> Actually I was thinking to a user defined buffer type:
>>
>> struct SurfaceBuffer
>> {
>>     void* data; // used as param to create the surface
>>     Rgba[] opIndex(size_t index);
>>     Rgba[][] scanline();
>> }
>>
>> that you would pass as data in 
>> cairo_image_surface_create_for_data().
>>
>> But gtk certainly has pitcure classes with the typical 
>> scanline method and that you could use in 
>> cairo_image_surface_create_for_data.
>
> Ahm, i am not quite sure if you and [Mike Wey] talk about the 
> same thing. And i posted the error message in my last post when 
> i try to call "cairo_image_surface_create_for_data". I still 
> don't know where i am able to call the function?

I've not followed the conversation since last time, but you can 
have a look at this:

https://github.com/BBasile/kheops/blob/master/src/kheops/bitmap.d#L143

this is how I do with Cairo only (even x11 is not implied since 
it's just a bitmap).
Then I can access pixels (for example to make shadows or blurs 
etc.) and do vectorial drawings as well with a context for the 
bitmap surface.