[cairo] cairo+DevIL ?

John Ellson john.ellson at comcast.net
Sat Aug 18 05:06:54 PDT 2007

Vladimir Vukicevic wrote:
> John Ellson wrote:
>> In a January 2007 posting
>> <http://lists.cairographics.org/archives/cairo/2007-January/009198.html>
>> Vlad suggested that DevIL
>>     <http://openil.sourceforge.net/>
>> would make a good backend for rendering other bitmap formats (gif, 
>> jpeg, tga, ...) from cairo.
>> Is this still the best-practice recommendation?   Is there any sample 
>> code out there?
>> I've made an initial attempt to bind the two together.  The problem 
>> I'm having at the moment
>> is that the in-memory data formats seem to be incompatible:
>> Do I really have to byte-twiddle the image data just to transfer 
>> between these two fine libraries?
> I'm not sure if there is a single best-practice recommendation; I've 
> certainly had good experience using DevIL in the past, though I have 
> never used it with cairo.  It's interesting that DevIL only provides 
> IL_RGBA and IL_BGRA; the documentation annoyingly states that these 
> formats are "self explanatory", which they are not.  Maybe IL_BGRA 
> happens to be compatible, if they're talking about byte order?
>     - Vlad
Both IL_BGRA and IL_RGBA result in black images.   The size of my image 
is right.   I'm attempting
to transfer the image data using:

        surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,120,60);
        rc = ilTexImage(
                        cairo_image_surface_get_width(surface), // Width
                        cairo_image_surface_get_height(surface),// Height
                        1,                                      // Depth
                        4,                                      // Bpp
                        IL_BGRA,                                // Format
                        IL_UNSIGNED_BYTE,                       // Type
                        cairo_image_surface_get_data(surface)   // Data

I'm just assuming my problem is byte-order, the DevIL documentation 
isn't very clear, I'm going to have to dig deeper
into the code.


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