[cairo] OPERATOR_SRC and no input
Stefan Krause
Stefan.Krause at gmx.at
Sun Jan 9 04:33:25 PST 2005
When I'm rendering a path that doesn't fill its bounding box completely
the image and xrender backend produces different output than the glitz
backend, e.g:
// fill background with white color
cairo_set_rgb_color (cr, 1.0, 1.0, 1.0);
cairo_set_alpha (cr, 1.0);
cairo_set_operator (cr, CAIRO_OPERATOR_SRC);
cairo_rectangle (cr, 0, 0, w, h);
cairo_fill (cr);
// now paint my path
cairo_set_operator (cr, CAIRO_OPERATOR_SRC);
cairo_set_alpha (cr, 1.0);
cairo_set_rgb_color (cr, 1.0, 0.0, 1.0);
cairo_move_to (cr, 100, 0);
cairo_line_to (cr, 200, 100);
cairo_line_to (cr, 100, 200);
cairo_line_to (cr, 0, 100);
cairo_close_path(cr);
cairo_fill(cr);
This will fill a path in a purple color and lets the background shine
through for the glitz backend. For the image and xrender backend the
bounding box of the path is filled black. I'd say glitz interpretation
of "no input" is correct, but you'll certainly know the Porter and Duff
rules better than I do.
Yours,
Stefan
More information about the cairo
mailing list