Richard Suchenwirth 2005-12-22 - The title says it all. Drawing lines in Tk is of course easiest in a canvas, but sometimes you might need to modify photo images, e.g. used for buttons or labels. The following function allows to draw a straight line (and, by repeated application, unfilled polygons) of selectable color (default: black) and width (default: 1).
proc photo'line {im x0 y0 x1 y1 args} {
array set "" {-color black -width 1}
array set "" $args
set dx [expr {$x1-$x0}]
set dy [expr {$y1-$y0}]
set dw [expr {$(-width)/2.}]
if {abs($dx)>abs($dy)} {
set d [expr {double($dy)/$dx}]
for {set x $x0} {$x<=$x1} {incr x} {
$im put $(-color) \
-to $x [expr {round($y0-$dw)}] \
[expr {$x+1}] [expr {round($y0+$dw)}]
set y0 [expr {$y0 + $d}]
}
} else {
set d [expr {double($dx)/$dy}]
for {set y $y0} {$y<=$y1} {incr y} {
$im put $(-color) \
-to [expr {round($x0-$dw)}] $y \
[expr {round($x0+$dw)}] [expr {$y+1}]
set x0 [expr {$x0 + $d}]
}
}
}#-- Testing:
package require Tk pack [canvas .c] set im [image create photo] $im put white -to 0 0 100 100 .c create image 5 5 -image $im -anchor nw photo'line $im 10 10 90 10 -color red -width 2 photo'line $im 10 10 90 90 -color green photo'line $im 10 10 10 90 -color blue -width 3