Tk Source Code

In library/palette.tcl the comment to the procedure ::tk::Darken claims, that colors can be brightened (tinted versus white), "50 means darken by 50%, 110 means brighten by 10%". However, [::tk::Darken #ff0000 150] again yields #ff0000.

Either the comment with respect to brightening should be removed. Or, the code should be changed along the following lines:

# ::tk::Darken --
# Given a color name, computes a new color value that darkens (or
# brightens) the given color by a given percent.
#
# Arguments:
# color -	Name of starting color.
# percent -	Integer telling how much to brighten or darken as a
#		percent: 50 means darken by 50%, 110 means brighten
#		by 10%.

proc ::tk::Darken {color percent} {
    if {percent < 0} {
	return "black"
    } elseif {percent > 200} {
	return "white"
    } elseif {percent <= 100} {
	foreach {red green blue} [winfo rgb . $color] {
	    set red [expr {($red/256)*$percent/100}]
	    set green [expr {($green/256)*$percent/100}]
	    set blue [expr {($blue/256)*$percent/100}]
	}
    } elseif {percent > 100} {
	foreach {red green blue} [winfo rgb . $color] {
	    set red [expr {255 - ((65535-$red)/256)*(200-$percent)/100}]
	    set green [expr {255 - ((65535-$green)/256)*(200-$percent)/100}]
	    set blue [expr {255 - ((65535-$blue)/256)*(200-$percent)/100}]
	}
    }
    return [format "#%02x%02x%02x" $red $green $blue]
}