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Ingy döt Net 2013-04-10 16:19:29 -07:00
parent e5e8880e41
commit 518da4a923
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Task/Bitmap-Midpoint-circle-algorithm/Tcl/bitmap-midpoint-circle-algorithm.tcl Normal file
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package require Tcl 8.5
package require Tk
proc drawCircle {image colour point radius} {
lassign $point x0 y0
setPixel $image $colour [list $x0 [expr {$y0 + $radius}]]
setPixel $image $colour [list $x0 [expr {$y0 - $radius}]]
setPixel $image $colour [list [expr {$x0 + $radius}] $y0]
setPixel $image $colour [list [expr {$x0 - $radius}] $y0]
set f [expr {1 - $radius}]
set ddF_x 1
set ddF_y [expr {-2 * $radius}]
set x 0
set y $radius
while {$x < $y} {
assert {$ddF_x == 2 * $x + 1}
assert {$ddF_y == -2 * $y}
assert {$f == $x*$x + $y*$y - $radius*$radius + 2*$x - $y + 1}
if {$f >= 0} {
incr y -1
incr ddF_y 2
incr f $ddF_y
}
incr x
incr ddF_x 2
incr f $ddF_x
setPixel $image $colour [list [expr {$x0 + $x}] [expr {$y0 + $y}]]
setPixel $image $colour [list [expr {$x0 - $x}] [expr {$y0 + $y}]]
setPixel $image $colour [list [expr {$x0 + $x}] [expr {$y0 - $y}]]
setPixel $image $colour [list [expr {$x0 - $x}] [expr {$y0 - $y}]]
setPixel $image $colour [list [expr {$x0 + $y}] [expr {$y0 + $x}]]
setPixel $image $colour [list [expr {$x0 - $y}] [expr {$y0 + $x}]]
setPixel $image $colour [list [expr {$x0 + $y}] [expr {$y0 - $x}]]
setPixel $image $colour [list [expr {$x0 - $y}] [expr {$y0 - $x}]]
}
}
# create the image and display it
set img [newImage 200 100]
label .l -image $img
pack .l
fill $img black
drawCircle $img blue {100 50} 49