[ulis], 2003-12-07. A proc to blur an image.

(this page replace the Blurring one)

[http://perso.wanadoo.fr/maurice.ulis/tcl/blur1.png]
[http://perso.wanadoo.fr/maurice.ulis/tcl/blur2.png]
[http://perso.wanadoo.fr/maurice.ulis/tcl/blur3.png]

(Original photo: [to fill])

----

'''How it works'''
  
  It works by adding some neighbor pixels:
  
     0  1  2  3  4
    .--.--.--.--.--.
  0 |//|  |  |  |//|
    .--.--.--.--.--.
  1 |  |  |//|  |  |
    .--.--.--.--.--.
  2 |  |//|XX|//|  |
    .--.--.--.--.--.
  3 |  |  |//|  |  |
    .--.--.--.--.--.
  4 |//|  |  |  |//|
    .--.--.--.--.--.

    The color of the central pixel is computed from all marked pixels:
    
  p22 = (1 - coef) * p22 
        + coef/8 * (p00 + p04 + p12 + p21 + p23 + p32 + p40 + p44)  
    
----

'''The proc'''

  namespace eval ::blur \
  {
    namespace export blur

    package require Tk

    proc blur {image coef} \
    {
      # check coef
      if {$coef < 0.0 || $coef > 1.0} \
      { error "bad coef \"$coef\": should be in the range 0.0, 1.0" }
      if {$coef < 1.e-5} { return $image }
      set coef2 [expr {$coef / 8.0}]
      # get the old image content
      set width [image width $image]
      set height [image height $image]
      if {$width * $height == 0} { error "bad image" }
      set data [$image data]
      # create corresponding planes
      for {set y 0} {$y < $height} {incr y} \
      {
        set r:row {}
        set g:row {}
        set b:row {}
        for {set x 0} {$x < $width} {incr x} \
        {
          foreach {r g b} [winfo rgb . [lindex $data $y $x]] break
          foreach c {r g b} { lappend $c:row [expr [set $c] / 256] }
        }
        foreach c {r g b} { lappend $c:data [set $c:row] }
      }
      # blurring
      for {set y 0} {$y < $height} {incr y} \
      {
        set row2 {}
        for {set x 0} {$x < $width} {incr x} \
        {
          foreach c {r g b} \
          { 
            set c00 [lindex [set $c:data] [expr {$y - 2}] [expr {$x - 2}]]
            set c01 [lindex [set $c:data] [expr {$y - 1}] [expr {$x - 0}]]
            set c02 [lindex [set $c:data] [expr {$y - 2}] [expr {$x + 2}]]
            set c10 [lindex [set $c:data] [expr {$y + 0}] [expr {$x - 1}]]
            set c11 [lindex [set $c:data] [expr {$y + 0}] [expr {$x - 0}]]
            set c12 [lindex [set $c:data] [expr {$y + 0}] [expr {$x + 1}]]
            set c20 [lindex [set $c:data] [expr {$y + 2}] [expr {$x - 2}]]
            set c21 [lindex [set $c:data] [expr {$y + 1}] [expr {$x - 0}]]
            set c22 [lindex [set $c:data] [expr {$y + 2}] [expr {$x + 2}]]
            foreach v {c00 c01 c02 c10 c12 c20 c21 c22} { if {[set $v] == ""} { set $v 0.0 } }
            set cc [expr {int((1.0 - $coef) * $c11 + $coef2 * ($c00 + $c01 + $c02 + $c10 + $c12 + $c20 + $c21 + $c22))}]
            if {$cc < 0} { set cc 0 }
            if {$cc > 255} { set cc 255 }
            set $c $cc
          }
          lappend row2 [format #%02x%02x%02x $r $g $b]
        }
        lappend data2 $row2
      }
      # create the new image
      set image2 [image create photo]
      # fill the new image
      $image2 put $data2
      # return the new image
      return $image2
    }

  }

----

'''The demo'''

  # to download the image:
  # http://perso.wanadoo.fr/maurice.ulis/tcl/image3.png

  package require Img
  image create photo Photo -file image3.png
  namespace import ::blur::blur
  wm withdraw .
  set n 0
  foreach coef {0.0 0.5 1.0} \
  {
    set image [blur Photo $coef]
    toplevel .$n
    wm title .$n "blur $coef"
    canvas .$n.c -bd 0 -highlightt 0
    .$n.c create image 0 0 -anchor nw -image $image
    foreach {- - width height} [.$n.c bbox all] break
    .$n.c config -width $width -height $height
    pack .$n.c
    bind .$n.c <Destroy> exit 
    update
    incr n
  }

----

'''See also'''

   * [Crisping an image]
   * [Expanding an image]
   * [Image Processing with HSV]
   * [Photo image rotation]
   * [Shrinking an image]

----

[Category Graphics]
|
[Category Image Processing]
|
[Arts and crafts of Tcl-Tk programming]
|
[Category Example]