Replaces old color with new color in the context in the area bounded by the rectangle x1, y1, x2, y2.
This is quite useful for highlighting a selected item in a list, or changing a selected color(s) in a multi colored area.
Also see flood_spill for operating on the current context.
| this |
the context |
| x1 |
the left edge of the bounding rectangle |
| y1 |
the top edge of the bounding rectangle |
| x2 |
the right edge of the bounding rectangle |
| y2 |
the bottom edge of the bounding rectangle |
| old_c |
the color to be replaced |
| new_c |
the new color |