Takes an existing pixbuf and adds an alpha channel to it.
If the existing pixbuf already had an alpha channel, the channel values are copied from the original; otherwise, the alpha channel is initialized to 255 (full opacity).
If `substitute_color` is `TRUE`, then the color specified by the (`r`, `g`, `b`) arguments will be assigned zero opacity. That is, if you pass `(255, 255, 255)` for the substitute color, all white pixels will become fully transparent.
If `substitute_color` is `FALSE`, then the (`r`, `g`, `b`) arguments will be ignored.
| this |
A Pixbuf. |
| substitute_color |
Whether to set a color to zero opacity. |
| r |
Red value to substitute. |
| g |
Green value to substitute. |
| b |
Blue value to substitute. |
|
A newly-created pixbuf |