Median filter: Difference between revisions
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→{{header|Wren}}: Changed to Wren S/H
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Line 4:
''(to test the function below, you can use these [[Read_ppm_file|input]] and [[Write_ppm_file|output]] solutions)''
=={{header|Action!}}==
{{libheader|Action! Bitmap tools}}
{{libheader|Action! Tool Kit}}
<syntaxhighlight lang="action!">INCLUDE "H6:LOADPPM5.ACT"
INCLUDE "D2:SORT.ACT" ;from the Action! Tool Kit
DEFINE HISTSIZE="256"
PROC PutBigPixel(INT x,y BYTE col)
IF x>=0 AND x<=79 AND y>=0 AND y<=47 THEN
y==LSH 2
col==RSH 4
IF col<0 THEN col=0
ELSEIF col>15 THEN col=15 FI
Color=col
Plot(x,y)
DrawTo(x,y+3)
FI
RETURN
PROC DrawImage(GrayImage POINTER image INT x,y)
INT i,j
BYTE c
FOR j=0 TO image.gh-1
DO
FOR i=0 TO image.gw-1
DO
c=GetGrayPixel(image,i,j)
PutBigPixel(x+i,y+j,c)
OD
OD
RETURN
INT FUNC Clamp(INT x,min,max)
IF x<min THEN
RETURN (min)
ELSEIF x>max THEN
RETURN (max)
FI
RETURN (x)
BYTE FUNC Median(BYTE ARRAY a BYTE len)
SortB(a,len,0)
len==RSH 1
RETURN (a(len))
PROC Median3x3(GrayImage POINTER src,dst)
INT x,y,i,j,ii,jj,index,sum
BYTE ARRAY arr(9)
BYTE c
FOR j=0 TO src.gh-1
DO
FOR i=0 TO src.gw-1
DO
sum=0 index=0
FOR jj=-1 TO 1
DO
y=Clamp(j+jj,0,src.gh-1)
FOR ii=-1 TO 1
DO
x=Clamp(i+ii,0,src.gw-1)
c=GetGrayPixel(src,x,y)
arr(index)=c
index==+1
OD
OD
c=Median(arr,9)
SetGrayPixel(dst,i,j,c)
OD
OD
RETURN
PROC Main()
BYTE CH=$02FC ;Internal hardware value for last key pressed
BYTE ARRAY dataIn(900),dataOut(900)
GrayImage in,out
INT size=[30],x,y
Put(125) PutE() ;clear the screen
InitGrayImage(in,size,size,dataIn)
InitGrayImage(out,size,size,dataOut)
PrintE("Loading source image...")
LoadPPM5(in,"H6:LENA30G.PPM")
PrintE("Median filter...")
Median3x3(in,out)
Graphics(9)
x=(40-size)/2
y=(48-size)/2
DrawImage(in,x,y)
DrawImage(out,x+40,y)
DO UNTIL CH#$FF OD
CH=$FF
RETURN</syntaxhighlight>
{{out}}
[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Median_filter.png Screenshot from Atari 8-bit computer]
=={{header|Ada}}==
<
type Extended_Luminance is range 0..10_000_000;
type VRGB is record
Line 65 ⟶ 166:
end loop;
return Result;
end Median;</
The implementation works with an arbitrary window width. The window is specified by its radius ''R''>0. The resulting width is 2''R''+1. The filter uses the original pixels of the image from the median of the window sorted according to the luminance. The image edges are extrapolated using the nearest pixel on the border. Sorting uses binary search. (For practical use, note that median filter is extremely slow.)
The following sample code illustrates use:
<
begin
Open (F1, In_File, "city.ppm");
Line 75 ⟶ 176:
Put_PPM (F2, Median (Get_PPM (F1), 1)); -- Window 3x3
Close (F1);
Close (F2);</
=={{header|BBC BASIC}}==
Line 82 ⟶ 183:
[[Image:greyscale_bbc.jpg|right]]
[[Image:median_bbc.jpg|right]]
<
Sort% = FN_sortinit(0,0)
Line 122 ⟶ 223:
REPEAT
WAIT 1
UNTIL FALSE</
=={{header|C}}==
O(n) filter with histogram.
<
#include <stdlib.h>
#include <fcntl.h>
Line 296 ⟶ 397:
return 0;
}</
=={{header|D}}==
Line 306 ⟶ 407:
Currently this code works only on greyscale images.
<
Image!Color medianFilter(uint radius=10, Color)(in Image!Color img)
pure nothrow @safe if (radius > 0) in {
assert(img.nx >= radius && img.ny >= radius);
} body {
alias Hist = uint[256];
static ubyte median(uint no)(in ref Hist cumulative)
pure nothrow @safe @nogc {
size_t localSum = 0;
foreach (immutable
if (v) {
localSum += v;
Line 327 ⟶ 431:
foreach (immutable y; 0 .. img.ny)
foreach (immutable x; 0 .. img.nx)
if (x < radius || x > img.nx - radius - 1 ||
y < radius || y > img.ny - radius - 1)
result[x, y] = img[x, y];
Line 373 ⟶ 477:
}
version (median_filter_main)
void main() { // Demo.
loadPGM!Gray(null, "lena.pgm").
.savePGM("lena_median_r10.pgm");
}</syntaxhighlight>
Compile with -version=median_filter_main to run the demo.
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
[[File:DelphiMedianFilter.png|frame|none]]
<syntaxhighlight lang="Delphi">
{-------------------------------------------------------------------------------}
type THistogram = record
Bins: array [0..255] of integer;
Colors: array [0..255] of TRGBTriple;
end;
procedure MedianFilter(Src,Dest: TBitmap; WindowX, WindowY: integer);
var x, y, X1, Y1, med, md, dl, delta_l, WX2, WY2: integer;
var I, MedSum, XStart,XEnd, YStart,YEnd, MedInx: integer;
var middle: integer;
var Histogram: THistogram;
var u: byte;
var Color: TRGBTriple;
var SrcRows,DestRows: TRGBTripleRowArray;
begin
WindowX:=WindowX * 2 -1;
WindowY:=WindowY * 2 -1;
Src.PixelFormat:=pf24Bit;
Dest.PixelFormat:=pf24Bit;
Dest.Width:=Src.Width;
Dest.Height:=Src.Height;
SetLength(SrcRows,Src.Height);
SetLength(DestRows,Dest.Height);
{Capture scan lines of both source and destiantion bitmaps}
for Y:=0 to Src.Height-1 do SrcRows[Y]:=Src.ScanLine[Y];
for Y:=0 to Dest.Height-1 do DestRows[Y]:=Dest.ScanLine[Y];
WX2 := WindowX div 2;
WY2 := WindowY div 2;
middle := (WindowX * WindowY-1) div 2;
for y := 0 to SRC.Height-1 do
begin
{ Determine the histogram and median for the first element of each row}
YStart:=Y - WY2;
YEnd:=Y + WY2;
{ histogram reset }
for I := 0 to 255 do Histogram.Bins[I] := 0;
{recalculation of the histogram for the start element row=y, col=0 }
for Y1 := YStart to YEnd do
for X1 := -WX2 to WX2 do
begin
{It is the first pixel on the row, so don't worry about right edge}
if (Y1>=0) and (Y1<SRC.Height) and (X1>=0) then Color:=SrcRows[Y1][X1] else Color:=MakeRBGTriple(0,0,0); // Color:=SrcRows[y][0];
U:=RGBToGray(Color);
inc(Histogram.Bins[U]);
Histogram.Colors[U]:=Color;
end;
{ now determine the median }
MedSum := 0;
for MedInx := 0 to 255 do
begin
inc(MedSum,Histogram.Bins[MedInx]);
if MedSum > middle then break;
end;
med := MedInx;
delta_l := MedSum - Histogram.Bins[MedInx];
DestRows[Y][0]:=Histogram.Colors[MedInx];
{ Loop through each column in this row}
for x := 1 to Src.Width-1 do
begin
XStart := x-wx2-1;
XEnd := x+wx2;
{ go to next column }
for Y1 := YStart to YEnd do
begin
if (XStart >= 0) and (Y1 >= 0) and (Y1 < SRC.Height) then Color:=SrcRows[Y1][XStart] else Color:=MakeRBGTriple(0,0,0); // Color:=SrcRows[Y][X];
U:=RGBToGray(Color);
if Histogram.Bins[u]>0 then dec(Histogram.Bins[u]);
if u < med then dec(delta_l);
if (XEnd < Src.Width) and (Y1 >= 0) and (Y1 < SRC.Height) then Color:=SrcRows[Y1][XEnd] else Color:=MakeRBGTriple(0,0,0); // Color:=SrcRows[Y][X];
U:=RGBToGray(Color);
inc(Histogram.Bins[u]);
Histogram.Colors[U]:=Color;
if u < med then inc(delta_l);
end;
{ update new median }
dl := delta_l;
md := med;
if dl > middle then
begin
while dl > middle do
begin
dec(md);
if Histogram.Bins[md] > 0 then
dec(dl,Histogram.Bins[md]);
end;
end
else
begin
while dl + Histogram.Bins[md] <= middle do
begin
if Histogram.Bins[md] > 0 then inc(dl,Histogram.Bins[md]);
inc(md);
end;
end;
delta_l := dl;
med := md;
DestRows[Y][X]:= Histogram.Colors[med];
end; { x loop}
end; { y loop}
end;
</syntaxhighlight>
{{out}}
<pre>
Elapsed Time: 110.287 ms.
</pre>
=={{header|GDL}}==
GDL has no inbuilt median filter function, which is native in IDL. This example is based on pseudocode here: http://en.wikipedia.org/wiki/Median_filter#2D_median_filter_pseudo_code, however, it works with 1D arrays only. It does not process boundaries.
<syntaxhighlight lang="gdl">
FUNCTION MEDIANF,ARRAY,WINDOW
RET=fltarr(N_ELEMENTS(ARRAY),1)
Line 399 ⟶ 637:
RETURN, RET
END
</syntaxhighlight>
Usage:
<
=={{header|Go}}==
Implemented with existing GetPx/SetPx functions at Grayscale image task. It could be sped up by putting code in the raster package, but if you're concerned about speed, you should implement one of the O(n) algorithms available.
<
// Files required to build supporting package raster are found in:
Line 493 ⟶ 732:
m := n / 2
return (kc[m-1] + kc[m]) / 2
}</
=={{header|J}}==
Line 500 ⟶ 739:
The following verbs are used to work with bitmaps:
<syntaxhighlight lang="j">
makeRGB=: 0&$: : (($,)~ ,&3)
toGray=: <. @: (+/) @: (0.2126 0.7152 0.0722 & *)"1
</syntaxhighlight>
We'll determine the window as a square zone around each pixel, with the given pixel in the center of the zone. Such a window always have odd height and width. We'll say the window radius is 0 if the window contain only the given pixel - in this case the resulting picture will be identical to the input. The radius is 1 if the window is 3x3 pixels, with given pixel in the center. Radius is 2 if the window is 5x5 pixels, with given pixel in the center, etc.
Line 509 ⟶ 748:
To get all pixels in the window, first calculate coordinates - or indexes - of those pixels. For the pixels on the edges of the input bitmap, include only those indexes which correspond to actually existing pixels - no negative indexes and no indexes outside of the bitmap boundaries.
<syntaxhighlight lang="j">
median_filter =: dyad define
win =. y -~ i. >: +: y
Line 519 ⟶ 758:
medians =. ({~ <. @ -: @ {. @ $) @ ({~ /: @: toGray) @ (,/) @ > sets
)
</syntaxhighlight>
Example:
<syntaxhighlight lang="j">
] bmp =. ?. 256 + makeRGB 4 5
34 39 168
Line 571 ⟶ 810:
142 156 125
116 139 217
</syntaxhighlight>
=={{header|
The class in the [[Bitmap]] task is reused for this task with an additional method to filter the image using the Wikipedia pseudo-code.
The program is tested with the left half of the sample image file, Medianfilterp.png, in the Wikipedia article.
<syntaxhighlight lang="java">
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.File;
import java.io.IOException;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import javax.imageio.ImageIO;
public final class MedianFilter {
public static void main(String[] aArgs) {
try {
BufferedImage image = ImageIO.read( new File("beforeFilter.png") );
BasicBitmapStorage bitmap = new BasicBitmapStorage(image.getWidth(null), image.getHeight(null));
for ( int y = 0; y < image.getHeight(null); y++ ) {
for ( int x = 0; x < image.getWidth(null); x++ ) {
bitmap.setPixel(x, y, new Color(image.getRGB(x, y), true));
}
}
bitmap.medianFilter(3, 3);
File fileAfterFilter = new File("afterFilter.png");
ImageIO.write((RenderedImage) bitmap.getImage(), "png", fileAfterFilter);
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
final class BasicBitmapStorage {
public BasicBitmapStorage(int aWidth, int aHeight) {
image = new BufferedImage(aWidth, aHeight, BufferedImage.TYPE_INT_RGB);
}
public void fill(Color aColor) {
Graphics graphics = image.getGraphics();
graphics.setColor(aColor);
graphics.fillRect(0, 0, image.getWidth(), image.getHeight());
}
public Color getPixel(int aX, int aY) {
return new Color(image.getRGB(aX, aY));
}
public void setPixel(int aX, int aY, Color aColor) {
image.setRGB(aX, aY, aColor.getRGB());
}
public Image getImage() {
return image;
}
public void medianFilter(int aWindowWidth, int aWindowHeight) {
List<Color> window = Stream.generate( () -> Color.BLACK )
.limit(aWindowWidth * aWindowHeight).collect(Collectors.toList());
final int edgeX = aWindowWidth / 2;
final int edgeY = aWindowHeight / 2;
Comparator<Color> luminanceComparator = (one, two) -> Double.compare(luminance(one), luminance(two));
for ( int x = edgeX; x < image.getWidth() - edgeX; x++ ) {
for ( int y = edgeY; y < image.getHeight() - edgeY; y++ ) {
int i = 0;
for ( int fx = 0; fx < aWindowWidth; fx++ ) {
for ( int fy = 0; fy < aWindowHeight; fy++ ) {
window.set(i, getPixel(x + fx - edgeX, y + fy - edgeY));
i += 1;
}
}
Collections.sort(window, luminanceComparator);
setPixel(x, y, window.get(aWindowWidth * aWindowHeight / 2));
}
}
}
private double luminance(Color aColor) {
return 0.2126 * aColor.getRed() + 0.7152 * aColor.getGreen() + 0.0722 * aColor.getBlue();
}
private final BufferedImage image;
}
</syntaxhighlight>
{{ out }}
[[Media:beforeFilter.png]] & [[Media:afterFilter.png]]
=={{header|Julia}}==
{{works with|Julia|0.6}}
<syntaxhighlight lang="julia">using Images, ImageFiltering, FileIO
Base.isless(a::RGB{T}, b::RGB{T}) where T =
red(a) < red(b) || green(a) < green(b) || blue(a) < blue(b)
Base.middle(x::RGB) = x
img = load("data/lenna100.jpg")
mapwindow(median!, img, (3, 3))</syntaxhighlight>
=={{header|Kotlin}}==
We reuse the class in the [[Bitmap]] task for this and add a member function to filter the image as per the Wikipedia pseudo-code. The colors in the Window array are sorted by their luminance.
To test the function we use the left half of the sample image file (Medianfilterp.png) in the Wikipedia article and see if we can get close to the right half.
<syntaxhighlight lang="scala">// Version 1.2.41
import java.awt.Color
import java.awt.Graphics
import java.awt.image.BufferedImage
import java.io.File
import javax.imageio.ImageIO
class BasicBitmapStorage(width: Int, height: Int) {
val image = BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR)
fun fill(c: Color) {
val g = image.graphics
g.color = c
g.fillRect(0, 0, image.width, image.height)
}
fun setPixel(x: Int, y: Int, c: Color) = image.setRGB(x, y, c.getRGB())
fun getPixel(x: Int, y: Int) = Color(image.getRGB(x, y))
fun medianFilter(windowWidth: Int, windowHeight: Int) {
val window = Array(windowWidth * windowHeight) { Color.black }
val edgeX = windowWidth / 2
val edgeY = windowHeight / 2
val compareByLuminance = {
c: Color -> 0.2126 * c.red + 0.7152 * c.green + 0.0722 * c.blue
}
for (x in edgeX until image.width - edgeX) {
for (y in edgeY until image.height - edgeY) {
var i = 0
for (fx in 0 until windowWidth) {
for (fy in 0 until windowHeight) {
window[i] = getPixel(x + fx - edgeX, y + fy - edgeY)
i++
}
}
window.sortBy(compareByLuminance)
setPixel(x, y, window[windowWidth * windowHeight / 2])
}
}
}
}
fun main(args: Array<String>) {
val img = ImageIO.read(File("Medianfilterp.png"))
val bbs = BasicBitmapStorage(img.width / 2, img.height)
with (bbs) {
for (y in 0 until img.height) {
for (x in 0 until img.width / 2) {
setPixel(x, y, Color(img.getRGB(x, y)))
}
}
medianFilter(3, 3)
val mfFile = File("Medianfilterp2.png")
ImageIO.write(image, "png", mfFile)
}
}</syntaxhighlight>
{{output}}
<pre>
Similar to right-half of Wikipedia image - color definition and brightness seem better but remaining distortion more evident.
</pre>
=={{header|Mathematica}}/{{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">MedianFilter[img,n]</syntaxhighlight>
=={{header|Nim}}==
{{trans|Kotlin}}
{{libheader|imageman}}
{{libheader|stb_image-Nim}}
<br>
Compile with command <code>nim c -d:imagemanlibpng=false -d:imagemanlibjpeg=false median_filter.nim</code> to
constrain "imageman" to use the library "stb_image" to open the PNG file. It seems that "imageman" internal
procedure has some difficulties to open PNG files using a palette.
<syntaxhighlight lang="nim">import algorithm
import imageman
func luminance(color: ColorRGBF64): float =
0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b
proc applyMedianFilter(img: var Image; windowWidth, windowHeight: Positive) =
var window = newSeq[ColorRGBF64](windowWidth * windowHeight)
let edgeX = windowWidth div 2
let edgeY = windowHeight div 2
for x in edgeX..<(img.width - edgeX):
for y in edgeY..<(img.height - edgeY):
var i = 0
for fx in 0..<windowWidth:
for fy in 0..<windowHeight:
window[i] = img[x + fx - edgeX, y + fy - edgeY]
inc i
window = window.sortedByIt(luminance(it))
img[x, y] = window[windowWidth * windowHeight div 2]
when isMainModule:
let fullImage = loadImage[ColorRGBF64]("Medianfilterp.png")
# Extract left part of the image.
var image = fullImage[0..<(fullImage.width div 2), 0..<fullImage.height]
image.applyMedianFilter(3, 3)
savePNG(image, "Medianfilterp_3x3.png")</syntaxhighlight>
=={{header|OCaml}}==
<
( (r1 + r2),
(g1 + g2),
Line 645 ⟶ 1,097:
done;
done;
(res)</
an alternate version of the function <tt>median_value</tt> using arrays instead of lists:
<
let samples = (radius*2+1) * (radius*2+1) in
let sample = Array.make samples (0,0,0) in
Line 667 ⟶ 1,119:
then sample.(mid+1)
else (color_div (color_add sample.(mid)
sample.(mid+1)) 2)</
=={{header|Perl}}==
<syntaxhighlight lang="perl">use strict 'vars';
use warnings;
use PDL;
use PDL::Image2D;
my $image = rpic 'plasma.png';
my $smoothed = med2d $image, ones(3,3), {Boundary => Truncate};
wpic $smoothed, 'plasma_median.png';</syntaxhighlight>
Compare offsite images: [https://github.com/SqrtNegInf/Rosettacode-Perl5-Smoke/blob/master/ref/plasma.png plasma.png] vs.
[https://github.com/SqrtNegInf/Rosettacode-Perl5-Smoke/blob/master/ref/plasma_median.png plasma_median.png]
=={{header|Phix}}==
{{trans|Go}}
Requires read_ppm() from [[Bitmap/Read_a_PPM_file#Phix|Read_a_PPM_file]], write_ppm() from [[Bitmap/Write_a_PPM_file#Phix|Write_a_PPM_file]],
which are both now part of demo\rosetta\ppm.e. Results may be verified with demo\rosetta\viewppm.exw
<syntaxhighlight lang="phix">-- demo\rosetta\Bitmap_Median_filter.exw
include ppm.e
constant neigh = {{-1,-1},{0,-1},{1,-1},
{-1, 0},{0, 0},{1, 0},
{-1, 1},{0, 1},{1, 1}}
--constant neigh = {{-2,-2},{-1,-2},{0,-2},{1,-2},{2,-2},
-- {-2,-1},{-1,-1},{0,-1},{1,-1},{2,-1},
-- {-2, 0},{-1, 0},{0, 0},{1, 0},{2, 0},
-- {-2, 1},{-1, 1},{0, 1},{1, 1},{2, 1},
-- {-2, 2},{-1, 2},{0, 2},{1, 2},{2, 2}}
sequence kn = repeat(0,length(neigh))
function median(sequence image)
integer h = length(image),
w = length(image[1])
for i=1 to length(image) do
for j=1 to length(image[i]) do
integer n = 0, c, p, x, y
for k=1 to length(neigh) do
x = i+neigh[k][1]
y = j+neigh[k][2]
if x>=1 and x<=h
and y>=1 and y<=w then
n += 1
c = image[x,j]
p = n
while p>1 do
if c>kn[p-1] then exit end if
kn[p] = kn[p-1]
p -= 1
end while
kn[p] = c
end if
end for
if and_bits(n,1) then
c = kn[(n+1)/2]
else
c = floor((kn[n/2]+kn[n/2+1])/2)
end if
image[i,j] = c
end for
end for
return image
end function
sequence img = read_ppm("Lena.ppm")
img = median(img)
write_ppm("LenaMedian.ppm",img)</syntaxhighlight>
=={{header|PicoLisp}}==
<
(let Len (inc (* 2 Radius))
(make
Line 700 ⟶ 1,221:
X ) )
(inc Radius) ) ) )
(map pop X) ) ) ) ) ) ) )</
Test using 'ppmRead' from [[Bitmap/Read a PPM file#PicoLisp]] and 'ppmWrite'
from [[Bitmap/Write a PPM file#PicoLisp]]:
Line 709 ⟶ 1,230:
{{libheader|PIL}}
<
im = Image.open('image.ppm')
median = im.filter(ImageFilter.MedianFilter(3))
median.save('image2.ppm')</
=={{header|Racket}}==
Due to the use of flomaps the solution below works for all types of images.
<syntaxhighlight lang="racket">
#lang racket
(require images/flomap math)
(define lena <<paste image of Lena here>> )
(define bm (send lena get-bitmap))
(define fm (bitmap->flomap bm))
(flomap->bitmap
(build-flomap
4 (send bm get-width) (send bm get-height)
(λ (k x y)
(define (f x y) (flomap-ref fm k x y))
(median < (list (f (- x 1) (- y 1))
(f (- x 1) y)
(f (- x 1) (+ y 1))
(f x (- y 1))
(f x y)
(f x (+ y 1))
(f (+ x 1) (- y 1))
(f (+ x 1) y)
(f (+ x 1) (+ y 1)))))))
</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
Clone of Perl 5, for now.
<syntaxhighlight lang="raku" line>use PDL:from<Perl5>;
use PDL::Image2D:from<Perl5>;
my $image = rpic 'plasma.png';
my $smoothed = med2d($image, ones(3,3), {Boundary => 'Truncate'});
wpic $smoothed, 'plasma_median.png';</syntaxhighlight>
Compare offsite images: [https://github.com/SqrtNegInf/Rosettacode-Perl6-Smoke/blob/master/ref/plasma-perl6.png plasma.png] vs.
[https://github.com/SqrtNegInf/Rosettacode-Perl6-Smoke/blob/master/ref/plasma_median.png plasma_median.png]
=={{header|Ruby}}==
{{trans|Tcl}}
<
def median_filter(radius=3)
radius += 1 if radius.even?
Line 783 ⟶ 1,342:
bitmap = Pixmap.open('file')
filtered = bitmap.median_filter</
=={{header|Tcl}}==
{{works with|Tcl|8.5}}
{{libheader|Tk}}
<
# Set the color of a pixel
Line 834 ⟶ 1,393:
update
pack [labelframe .dst -text Median] -side left
pack [label .dst.l -image [medianFilter teapot]]</
=={{header|Wren}}==
{{libheader|DOME}}
This follows the Wikipedia pseudo-code for the median filter, sorting the colors by their luminance, and displays the 'before' and 'after' images side by side on the canvas. Results are as expected though remaining corruption seems more prominent than on Wikipedia image.
<syntaxhighlight lang="wren">import "graphics" for Canvas, ImageData, Color
import "dome" for Window
class MedianFilter {
construct new(filename, filename2, windowWidth, windowHeight) {
Window.title = "Median filter"
var image = ImageData.loadFromFile(filename)
Window.resize(image.width, image.height)
Canvas.resize(image.width, image.height)
_ww = windowWidth
_wh = windowHeight
// split off the left half
_image = ImageData.create(filename2, image.width/2, image.height)
_name = filename2
for (x in 0...image.width/2) {
for (y in 0...image.height) _image.pset(x, y, image.pget(x, y))
}
// display it on the left before filtering
_image.draw(0, 0)
}
luminance(c) { 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b }
medianFilter(windowWidth, windowHeight) {
var window = List.filled(windowWidth * windowHeight, Color.black)
var edgeX = (windowWidth / 2).floor
var edgeY = (windowHeight / 2).floor
var comparer = Fn.new { |a, b| luminance(a) < luminance(b) }
for (x in edgeX..._image.width - edgeX) {
for (y in edgeY..._image.height - edgeY) {
var i = 0
for (fx in 0...windowWidth) {
for (fy in 0...windowHeight) {
window[i] = _image.pget(x + fx - edgeX, y + fy - edgeY)
i = i + 1
}
}
window.sort(comparer)
_image.pset(x, y, window[((windowWidth * windowHeight)/2).floor])
}
}
}
init() {
medianFilter(_ww, _wh)
// display it on the right after filtering
_image.draw(_image.width, 0)
// save it to a file
_image.saveToFile(_name)
}
update() {}
draw(alpha) {}
}
var Game = MedianFilter.new("Medianfilterp.png", "Medianfilterp2.png", 3, 3)</syntaxhighlight>
=={{header|zkl}}==
Uses Image Magick and the PPM class from http://rosettacode.org/wiki/Bitmap/Bresenham%27s_line_algorithm#zkl
<syntaxhighlight lang="zkl">fcn medianFilter(img){ //-->new image
var [const] window=[-2..2].walk(), edge=(window.len()/2); // 5x5 window
MX,MY,new := img.w,img.h,PPM(MX,MY);
pixel,pixels:=List(),List();
foreach x,y in ([edge..MX-edge-1],[edge..MY-edge-1]){
pixels.clear();
foreach ox,oy in (window,window){ // construct sorted list as pixels are read.
pixels.merge(pixel.clear(img[x+ox, y+oy])); // merge sort two lists
}
new[x,y]=pixels[4]; // median value
}
new
}</syntaxhighlight>
<syntaxhighlight lang="zkl">filtered:=medianFilter(PPM.readJPGFile("lena.jpg"));
filtered.writeJPGFile("lenaMedianFiltered.zkl.jpg");</syntaxhighlight>
See the [http://www.zenkinetic.com/Images/RosettaCode/lenaMedianFiltered.zkl.jpg filtered image]
and the [http://www.zenkinetic.com/Images/RosettaCode/lena.jpg orginal].
{{omit from|PARI/GP}}
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