GPS: This code draws gradients that look like the image below.
[todo making screenshot, please don't edit yet.]
proc + {n1 n2} {
expr {$n1 + $n2}
}
proc - {n1 n2} {
expr {$n1 - $n2}
}
proc * {n1 n2} {
expr {$n1 * $n2}
}
proc / {n1 n2} {
expr {$n1 / $n2}
}
proc toInt {n} {
expr int($n)
}
proc drawGradient {win type col1Str col2Str} {
$win delete gradient
set width [winfo width $win]
set height [winfo height $win]
foreach {r1 g1 b1} [winfo rgb $win $col1Str] break
foreach {r2 g2 b2} [winfo rgb $win $col2Str] break
set rRange [- $r2.0 $r1]
set rRatio [/ $rRange $width]
set gRange [- $g2.0 $g1]
set gRatio [/ $gRange $width]
set bRange [- $b2.0 $b1]
set bRatio [/ $bRange $width]
if {$type == "x"} {
for {set x 0} {$x < $width} {incr x} {
set nR [toInt [+ $r1 [* $rRatio $x]]]
set nG [toInt [+ $g1 [* $gRatio $x]]]
set nB [toInt [+ $b1 [* $bRatio $x]]]
set col [format {%4.4x} $nR]
append col [format {%4.4x} $nG]
append col [format {%4.4x} $nB]
$win create line $x 0 $x $height -tags gradient -fill #${col}
}
} else {
for {set y 0} {$y < $height} {incr y} {
set nR [toInt [+ $r1 [* $rRatio $y]]]
set nG [toInt [+ $g1 [* $gRatio $y]]]
set nB [toInt [+ $b1 [* $bRatio $y]]]
set col [format {%4.4x} $nR]
append col [format {%4.4x} $nG]
append col [format {%4.4x} $nB]
$win create line 0 $y $width $y -tags gradient -fill #${col}
}
}
return $win
}
canvas .grad1
bind .grad1 <Configure> [list drawGradient .grad1 x red royalblue]
canvas .grad2
bind .grad2 <Configure> [list drawGradient .grad2 x yellow red]
pack .grad1 .grad2 -fill both -expand 1