Replaces old color with new color in the current 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.
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 |