HJG I have some images on a canvas, and I want to get the color of the pixel under the cursor.
Right now, this works only for an image placed on the canvas at 0,0 :
package require Img
proc int x { expr int($x) }
proc ShowPixel {x y i} {
set c "- - -"
catch { set c [$::img1 get $x $y] }
wm title . "$x $y #$i : $c"
}
proc ShowColor {w x y} {
# idea: RS
set color ""
set id [$w find withtag current]
if {$id>0} {
set xx $x
set yy $y
foreach {x0 y0 x1 y1} [$w bbox $id] break
incr xx -$x0
incr yy -$x0
#wm title . "$x $y #$id : $x0 $y0 $x1 $y1 : $xx $yy"
#return
switch -- [$w type $id] {
image {set color [[$w itemcget $id -image] get $xx $yy]}
line - polygon - rectangle - oval {
set color [$w itemcget $id -fill]
}
}
wm title . "$x $y #$id $xx $yy = $color"
} else {
wm title . "$x $y"
}
#return $color
}
set fn gosmall.gif
set img1 [image create photo -file $fn]
pack [canvas .c]
.c create image 0 0 -image $img1 -anchor nw -tag Copy1
.c create image 80 80 -image $img1 -anchor nw -tag Copy2
.c create rect 125 25 145 45 -fill red
.c create oval 25 125 45 145 -fill green
.c create line 15 100 70 120 -fill blue
.c create poly 100 65 140 65 100 20 -fill cyan -outline black
#bind .c <Motion> { ShowPixel [int [%W canvasx %x]] [int [%W canvasy %y]] [%W find withtag current] }
bind .c <Motion> { ShowColor %W [int [%W canvasx %x]] [int [%W canvasy %y]] }Using proc ShowPixel, the RGB-values of the pixel under the cursor are shown only for the first copy of the image...
I can query the coordinates of an item/image on the canvas with bbox (to adjust coordinates within the image vs. the screen-coordinates given by the cursor), but how do I pass the item (as opposed to its id) to the proc ShowPixel ?
RS: Pass in the widget name. For images you can retrieve the name as -image attribute.
HJG: Ok - proc ShowColor now does mostly what I wanted, but gives an error "coordinates out of range" at the edge of the images.
And for rect / oval etc. it would be nice to also get the RGB-values...