Bitmap/Histogram: Difference between revisions

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* Replace each pixel of luminance lesser than the median to black, and others to white.

Use [[read ppm file | read]]/[[write ppm file]], and [[grayscale image]] solutions.

=={{header|Action!}}==

In the following solution the input file [https://gitlab.com/amarok8bit/action-rosetta-code/-/blob/master/source/lena30g.PPM lena30g.PPM] is loaded from H6 drive. Altirra emulator automatically converts CR/LF character from ASCII into 155 character in ATASCII charset used by Atari 8-bit computer when one from H6-H10 hard drive under DOS 2.5 is used.

<syntaxhighlight lang=~~Action~~!>INCLUDE "H6:LOADPPM5.ACT"

<syntaxhighlight lang="action!">INCLUDE "H6:LOADPPM5.ACT"

DEFINE HISTSIZE="256"

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[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Bitmap_Histogram.png Screenshot from Atari 8-bit computer]

=={{header|Ada}}==

Histogram of an image:

<syntaxhighlight lang=ada>type Pixel_Count is mod 2**64;

<syntaxhighlight lang="ada">type Pixel_Count is mod 2**64;

type Histogram is array (Luminance) of Pixel_Count;

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end Get_Histogram;</syntaxhighlight>

Median of a histogram:

<syntaxhighlight lang=ada>function Median (H : Histogram) return Luminance is

<syntaxhighlight lang="ada">function Median (H : Histogram) return Luminance is

From : Luminance := Luminance'First;

To : Luminance := Luminance'Last;

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end Median;</syntaxhighlight>

Conversion of an image to black and white art:

<syntaxhighlight lang=ada> F1, F2 : File_Type;

<syntaxhighlight lang="ada"> F1, F2 : File_Type;

begin

Open (F1, In_File, "city.ppm");

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end;

Close (F2);</syntaxhighlight>

=={{header|BBC BASIC}}==

[[Image:greyscale_bbc.jpg|right]]

[[Image:histogram_bbc.gif|right]]

<syntaxhighlight lang=bbcbasic> INSTALL @lib$+"SORTLIB"

<syntaxhighlight lang="bbcbasic"> INSTALL @lib$+"SORTLIB"

Sort% = FN_sortinit(0,0)

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SWAP ?^col%,?(^col%+2)

= col%</syntaxhighlight>

=={{header|C}}==

<syntaxhighlight lang=c>typedef unsigned int histogram_t;

<syntaxhighlight lang="c">typedef unsigned int histogram_t;

typedef histogram_t *histogram;

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luminance histogram_median(histogram h);</syntaxhighlight>

<syntaxhighlight lang=c>histogram get_histogram(grayimage im)

<syntaxhighlight lang="c">histogram get_histogram(grayimage im)

{

histogram t;

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<syntaxhighlight lang=c>luminance histogram_median(histogram h)

<syntaxhighlight lang="c">luminance histogram_median(histogram h)

{

luminance From, To;

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An example of usage is the following code.

<syntaxhighlight lang=c>#include <stdio.h>

<syntaxhighlight lang="c">#include <stdio.h>

#include <stdlib.h>

#include "imglib.h"

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Which reads from the file specified from the command line and outputs to the standard out the PPM B/W version of the input image. The input image can be of any format handled by ImageMagick (see [[Read image file through a pipe]])

=={{header|Common Lisp}}==

<syntaxhighlight lang=lisp>(defpackage #:histogram

<syntaxhighlight lang="lisp">(defpackage #:histogram

(:use #:cl

#:opticl))

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(bw-image (gray->black&white-image (color->gray-image image))))

(write-pbm-file "lenna-bw.pbm" bw-image)))</syntaxhighlight>

=={{header|D}}==

It uses the grayscale_image from the Grayscale image Task. The loaded frog image is from the Color quantization Task.

<syntaxhighlight lang=d>import grayscale_image;

<syntaxhighlight lang="d">import grayscale_image;

Color findSingleChannelMedian(Color)(in Image!Color img)

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.savePGM("quantum_frog_bin.pgm");

}</syntaxhighlight>

=={{header|FBSL}}==

FBSL volatiles and function call concatenation used heavily for brevity.

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'''24-bpp P.O.T.-size BMP solution:'''

[[File:FBSLHistogram.PNG|right]]

<syntaxhighlight lang=qbasic>#DEFINE WM_CLOSE 16

<syntaxhighlight lang="qbasic">#DEFINE WM_CLOSE 16

DIM colored = ".\LenaClr.bmp", grayscale = ".\LenaGry.bmp", blackwhite = ".\LenaBnw.bmp"

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FILEPUT(FILEOPEN(blackwhite, BINARY_NEW), FILEGET): FILECLOSE(FILEOPEN) ' save b/w image

END SUB</syntaxhighlight>

=={{header|Forth}}==

<syntaxhighlight lang=forth>: histogram ( array gmp -- )

<syntaxhighlight lang="forth">: histogram ( array gmp -- )

over 256 cells erase

dup bdim * over bdata + swap bdata

do 1 over i c@ cells + +! loop drop ;</syntaxhighlight>

=={{header|Fortran}}==

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'''Note''': ''luminance'' range is hard-encoded and is from 0 to 255. This could be enhanced.

<syntaxhighlight lang=fortran>module RCImageProcess

<syntaxhighlight lang="fortran">module RCImageProcess

use RCImageBasic

implicit none

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Example:

<syntaxhighlight lang=fortran>program BasicImageTests

<syntaxhighlight lang="fortran">program BasicImageTests

use RCImageBasic

use RCImageIO

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end program BasicImageTests</syntaxhighlight>

=={{header|Go}}==

Histogram and Threshold functions are be added to the Grmap type for this task:

<syntaxhighlight lang=go>package raster

<syntaxhighlight lang="go">package raster

import "math"

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}</syntaxhighlight>

Demonstration program computes the median:

<syntaxhighlight lang=go>package main

<syntaxhighlight lang="go">package main

// Files required to build supporting package raster are found in:

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}

}</syntaxhighlight>

=={{header|Haskell}}==

First, an implementation of a black-and-white instance of <tt>Color</tt>. For simplicty, we use ASCII PBM for output instead of the raw format.

<syntaxhighlight lang=haskell>module Bitmap.BW(module Bitmap.BW) where

<syntaxhighlight lang="haskell">module Bitmap.BW(module Bitmap.BW) where

import Bitmap

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Every instance of <tt>Color</tt> has a <tt>luminance</tt> method, so we don't need to convert an image to <tt>Gray</tt> to calculate its histogram.

<syntaxhighlight lang=haskell>import Bitmap

<syntaxhighlight lang="haskell">import Bitmap

import Bitmap.RGB

import Bitmap.BW

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then (n + 1, left + l, right, ls, rL)

else (n, left, right + r, lL, rs)</syntaxhighlight>

=={{header|J}}==

'''Solution:'''

Using <code>toGray</code> from [[Grayscale image#J|Grayscale image]].

<syntaxhighlight lang=j>getImgHist=: ([: /:~ ~. ,. #/.~)@,

<syntaxhighlight lang="j">getImgHist=: ([: /:~ ~. ,. #/.~)@,

medianHist=: {."1 {~ [: (+/\ I. -:@(+/)) {:"1

toBW=: 255 * medianHist@getImgHist < toGray</syntaxhighlight>

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Use [http://rosettacode.org/mw/images/b/b6/Lenna100.jpg Lenna100.jpg] for testing (read using the [[j:Addons/media/platimg|media/platimg]] addon and convert to ppm file).

<syntaxhighlight lang=j> require 'media/platimg'

<syntaxhighlight lang="j"> require 'media/platimg'

'Lenna100.ppm' writeppm~ 256#.inv readimg 'Lenna100.jpg'

786447</syntaxhighlight>

Read ppm file, convert to black and white and write to a new ppm file using <code>writeppm</code>, <code>readppm</code> and <code>toColor</code> from the [[read ppm file#J | read]]/[[write ppm file#J|write ppm file]], and [[grayscale image#J|grayscale image]] solutions.

<syntaxhighlight lang=j> 'Lenna100BW.ppm' writeppm~ toColor toBW readppm 'Lenna100.ppm'

<syntaxhighlight lang="j"> 'Lenna100BW.ppm' writeppm~ toColor toBW readppm 'Lenna100.ppm'

786447</syntaxhighlight>

=={{header|Java}}==

<syntaxhighlight lang=~~Java~~>import java.awt.image.BufferedImage;

<syntaxhighlight lang="java">import java.awt.image.BufferedImage;

import java.io.File;

import java.io.IOException;

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}

}</syntaxhighlight>

=={{header|Julia}}==

<syntaxhighlight lang=julia>using Images, FileIO

<syntaxhighlight lang="julia">using Images, FileIO

ima = load("data/lenna50.jpg")

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imb[imb .> medcol] = Gray(1.0)

save("data/lennaGray.jpg", imb)</syntaxhighlight>

=={{header|Kotlin}}==

Uses the image from the [[Percentage difference between images]] task as an example.

<syntaxhighlight lang=scala>// version 1.2.10

<syntaxhighlight lang="scala">// version 1.2.10

import java.io.File

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ImageIO.write(image, "jpg", bwFile)

}</syntaxhighlight>

=={{header|Lua}}==

This solution uses functions defined at:

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[[Basic bitmap storage#Lua]],

[[Grayscale image#Lua]].

<syntaxhighlight lang=lua>function Histogram( image )

<syntaxhighlight lang="lua">function Histogram( image )

local size_x, size_y = #image, #image[1]

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bitmap = ConvertToColorImage( gray_im )

Write_PPM( "outputimage.ppm", bitmap )</syntaxhighlight>

=={{header|Mathematica}}/{{header|Wolfram Language}}==

<syntaxhighlight lang=~~Mathematica~~>ImageLevels[img]</syntaxhighlight>

<syntaxhighlight lang="mathematica">ImageLevels[img]</syntaxhighlight>

=={{header|Nim}}==

<syntaxhighlight lang=~~Nim~~>import bitmap

<syntaxhighlight lang="nim">import bitmap

import grayscale_image

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# Save image as a PPM file.

image.writePPM("house_bw.ppm")</syntaxhighlight>

=={{header|OCaml}}==

<syntaxhighlight lang=ocaml>type histogram = int array

<syntaxhighlight lang="ocaml">type histogram = int array

let get_histogram ~img:gray_channel =

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;;</syntaxhighlight>

<syntaxhighlight lang=ocaml>let histogram_median (h : histogram) =

<syntaxhighlight lang="ocaml">let histogram_median (h : histogram) =

let from = 0 and to_ = 255 in

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main:

<syntaxhighlight lang=ocaml>let () =

<syntaxhighlight lang="ocaml">let () =

let img = read_ppm ~filename:"/tmp/foo.ppm" in

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output_ppm ~oc:stdout ~img:res;

;;</syntaxhighlight>

=={{header|Octave}}==

'''Using package''' [http://octave.sourceforge.net/image/index.html Image]

<syntaxhighlight lang=octave>function h = imagehistogram(imago)

<syntaxhighlight lang="octave">function h = imagehistogram(imago)

if ( isgray(imago) )

for j = 0:255

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ibw( img <= m ) = 0;

jpgwrite("lennamed.jpg", ibw, 100);</syntaxhighlight>

=={{header|Phix}}==

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]]. <br>

Uses demo\rosetta\lena.ppm, included in the distribution, results may be verified with demo\rosetta\viewppm.exw

<syntaxhighlight lang=~~Phix~~>-- demo\rosetta\Bitmap_Histogram.exw (runnable version)

<syntaxhighlight lang="phix">-- demo\rosetta\Bitmap_Histogram.exw (runnable version)

include ppm.e -- black, white, read_ppm(), write_ppm() (covers above requirements)

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img = to_bw(img)

write_ppm("LenaBW.ppm",img)</syntaxhighlight>

=={{header|PHP}}==

define('src_name', 'input.jpg'); // source image

define('dest_name', 'output.jpg'); // destination image

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</i>

</div>

=={{header|PicoLisp}}==

<syntaxhighlight lang=~~PicoLisp~~>(de histogram (Pgm)

<syntaxhighlight lang="picolisp">(de histogram (Pgm)

(let H (need 256 0)

(for L Pgm

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(inc (nth H (inc G))) ) )

H ) )</syntaxhighlight>

=={{header|PureBasic}}==

Also requires PureBasic solutions for [[Bitmap/Read_a_PPM_file#PureBasic|Read a PPM file]], [[Grayscale_image#PureBasic|Grayscale image]], and [[Bitmap/Write_a_PPM_file#PureBasic|Write a PPM file]].

<syntaxhighlight lang=~~PureBasic~~>Procedure getHistogram(image, Array histogram(1))

<syntaxhighlight lang="purebasic">Procedure getHistogram(image, Array histogram(1))

Protected w = ImageWidth(image) - 1

Protected h = ImageHeight(image) - 1

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SaveImageAsPPM(image, outputFile, 1)

EndIf</syntaxhighlight>

=={{header|Python}}==

Makes use of the Pillow library (PIL) you can install it using pip. The code is probably not the fastest or the image I used (1960x1960) is just too big.

<syntaxhighlight lang=python>from PIL import Image

<syntaxhighlight lang="python">from PIL import Image

# Open the image

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bw_image.show()

bm_image.show()</syntaxhighlight>

=={{header|Racket}}==

<syntaxhighlight lang=racket> #lang racket

<syntaxhighlight lang="racket"> #lang racket

(require racket/draw math/statistics racket/require

(filtered-in

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Sorry guys... I just give up on linking/displaying these images any other way!

=={{header|Raku}}==

(formerly Perl 6)

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Uses pieces from [[Bitmap#Raku| Bitmap]], [[Bitmap/Write_a_PPM_file#Raku| Write a PPM file]] and [[Grayscale_image#Raku| Grayscale image]] tasks. Included here to make a complete, runnable program.

<syntaxhighlight lang=raku line>class Pixel { has UInt ($.R, $.G, $.B) }

<syntaxhighlight lang="raku" line>class Pixel { has UInt ($.R, $.G, $.B) }

class Bitmap {

has UInt ($.width, $.height);

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See [https://github.com/thundergnat/rc/blob/master/img/Lenna.png Lenna], and [https://github.com/thundergnat/rc/blob/master/img/Lenna-bw.png Lenna-bw] images. (converted to .png as .ppm format is not widely supported).

=={{header|Ruby}}==

<syntaxhighlight lang=ruby>class Pixmap

<syntaxhighlight lang="ruby">class Pixmap

def histogram

histogram = Hash.new(0)

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Pixmap.open('file.ppm').save_as_blackandwhite('file_bw.ppm')</syntaxhighlight>

=={{header|Rust}}==

<syntaxhighlight lang=rust>extern crate image;

<syntaxhighlight lang="rust">extern crate image;

use image::{DynamicImage, GenericImageView, ImageBuffer, Rgba};

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}

</syntaxhighlight>

=={{header|Scala}}==