[cairo] Image surface : BGRA or ARGB ?

[Timothée Lecomte]

Hi

I have noticed a difference between the documentation and the actual
behaviour of cairo_image_surface_create_for_data().

The buffer is supposed to be in the format ARGB :

"CAIRO_FORMAT_ARGB32 	 each pixel is a 32-bit quantity, with alpha in the
upper 8 bits, then red, then green, then blue."

However, in practise, I found it to be BGRA.

Test case (cr is the actual context where you will want to draw on):

	unsigned char * image255;
	cairo_surface_t *image_surface;
	cairo_pattern_t *pattern;
	cairo_matrix_t matrix;

	/* cairo image buffer, in the format BGRABGRA... */
	image255 = (unsigned char*) malloc(4*sizeof(unsigned char));
	*(image255) = 1;
	*(image255 +1) = 0;
	*(image255 +2) = 1;
	*(image255 +3) = 0;

	image_surface = cairo_image_surface_create_for_data(image255,
CAIRO_FORMAT_RGB24, 1, 1, 4*1);

	double scale_x = 1./100;
	double scale_y = 1./100;

	pattern = cairo_pattern_create_for_surface( image_surface );
	cairo_pattern_set_filter(pattern,CAIRO_FILTER_FAST);
	cairo_matrix_init_scale(&matrix,scale_x,scale_y);
	cairo_pattern_set_matrix(pattern,&matrix);
	cairo_set_source(cr,pattern);
	cairo_paint(cr);
	cairo_pattern_destroy(pattern);
	cairo_surface_destroy(image_surface);
	free(image255);


Is the problem in my code, in cairo code or in the cairo doc ?
Should I post a bug report for it ?

Best regards,

Timothée