Bitmap/Read an image through a pipe

From Rosetta Code
Bitmap/Read an image through a pipe
You are encouraged to solve this task according to the task description, using any language you may know.

This task is the opposite of the PPM conversion through a pipe. In this task, using a delegate tool (like cjpeg, one of the netpbm package, or convert of the ImageMagick package) we read an image file and load it into the data storage type defined here. We can also use the code from Read ppm file, so that we can use PPM format like a (natural) bridge between the foreign image format and our simple data storage.


I use the magick command from ImageMagick. You need all the source files from Bitmap#ATS, Bitmap/Read_a_PPM_file#ATS, and Bitmap/Write_a_PPM_file#ATS. (You do not need the files from Grayscale_image#ATS.)

Because I wrote this program by modifying Bitmap/PPM_conversion_through_a_pipe#ATS, it both reads and writes the file by piping through the magick command of ImageMagick. The comments at the top of the earlier program thus apply doubly here.

(* I both read AND write the image through pipes connected to
   ImageMagick. One can also pass options and such but I won't go into
   the details. *)


patscc -std=gnu2x -g -O2 -DATS_MEMALLOC_LIBC \
  -o $fname($1) $1 \


#include "share/atspre_staload.hats"

staload "bitmap_task.sats"
staload "bitmap_read_ppm_task.sats"
staload "bitmap_write_ppm_task.sats"

staload _ = "bitmap_task.dats"
staload _ = "bitmap_read_ppm_task.dats"
staload _ = "bitmap_write_ppm_task.dats"

(* There is support for pipe-I/O in libats/libc, but I cannot (at
   least when in a hurry) figure out how it is supposed to be
   used. So, as elsewhere in the "raster graphics operations"
   category, what is not in the prelude itself I implement with the
   foreign function interfaces. :) Using FFI is a typical part of ATS
   programming, and one should get used to doing it.
   Anyway, here is some UNSAFE support for pipe-I/O. *)

typedef charstar = $extype"char *"
typedef FILEstar = $extype"FILE *"

fn {}
fileref_popen_unsafe (command : string,
                      mode    : string)
    : Option_vt FILEref =
    val p = $extfcall (ptr, "popen", $UNSAFE.cast{charstar} command,
                       $UNSAFE.cast{charstar} mode)
    if iseqz p then
      None_vt ()
      Some_vt ($UNSAFE.cast{FILEref} p)

fn {}
fileref_pclose_unsafe (f : FILEref)
    : int =              (* Returns the exit status of the command. *)
  $extfcall (int, "pclose", $UNSAFE.cast{FILEstar} f)


main0 (argc, argv) =
    val args = listize_argc_argv (argc, argv)
    val nargs = length args

    val inpf_name = if nargs < 2 then "-" else args[1]
    val command = string_append ("magick ", inpf_name, " ppm:-")
    val pipe_opt =
      (* Temporarily treating a strptr as a string, just to make a
         function call of this sort, is not actually unsafe. *)
      fileref_popen_unsafe ($UNSAFE.strptr2string command, "r")
    val () = free command
    case+ pipe_opt of
    | ~ None_vt () =>
        free args;
        println! ("For some reason, I failed to open a pipe ",
                  "for reading from magick.");
        exit 1
    | ~ Some_vt inpf =>
        val pix_opt = pixmap_read_ppm<rgb24> inpf
        ignoret (fileref_pclose_unsafe inpf);
        case+ pix_opt of
        | ~ None_vt () =>
            free args;
            println! ("For some reason, I failed to pipe the image ",
                      "from magick.");
            exit 1
        | ~ Some_vt @(pfgc1 | pix1) =>
            val outf_name = if nargs < 3 then "-" else args[2]
            val command = string_append ("magick ppm:- ", outf_name)
            val () = free args
            val pipe_opt =
              (* Temporarily treating a strptr as a string, just to
                 make a function call of this sort, is not actually
                 unsafe. *)
                ($UNSAFE.strptr2string command, "w")
            val () = free command
            case+ pipe_opt of
            | ~ None_vt () =>
                free (pfgc1 | pix1);
                println! ("For some reason, I failed to open a pipe ",
                          "for writing to magick.");
                exit 3
            | ~ Some_vt outf =>
                val success = pixmap_write_ppm<rgb24> (outf, pix1)
                ignoret (fileref_pclose_unsafe outf);
                free (pfgc1 | pix1);
                if ~success then
                    println! ("For some reason, I failed to pipe ",
                              "the image to magick.");
                    exit 2

Using SIPI test image 4.1.07:

$ myatscc bitmap_read_through_pipe_task.dats
$ ./bitmap_read_through_pipe_task 4.1.07.tiff > 4.1.07.ppm
$ file 4.1.07.ppm
4.1.07.ppm: Netpbm image data, size = 256 x 256, rawbits, pixmap
$ ./bitmap_read_through_pipe_task 4.1.07.tiff 4.1.07.jpg
$ file 4.1.07.jpg
4.1.07.jpg: JPEG image data, JFIF standard 1.01, aspect ratio, density 1x1, segment length 16, baseline, precision 8, 256x256, components 3

Notice that, when I did not specify an output file, I got a PPM (PPM being what was sent through the output pipe to magick). Both times, though, the input pipe converts a TIFF image to PPM, which then is read into the internal pixmap type.

Here is the JPEG that was outputted:

SIPI test image of jellybeans.


Works with: AutoHotkey_L

Uses StdoutTovar.ahk

ppm := Run("cmd.exe /c convert lena50.jpg ppm:-") 
                       ; pipe in from imagemagick
img := ppm_read("", ppm) ;   
x := img[4,4] ; get pixel(4,4)
y := img[24,24] ; get pixel(24,24)
msgbox % x.rgb() " " y.rgb()
ppm_read(filename, ppmo=0) ; only ppm6 files supported 
if !ppmo  ; if image not already in memory, read from filename
  fileread, ppmo, % filename 

  index := 1  
  pos := 1

  loop, parse, ppmo, `n, `r
    if (substr(A_LoopField, 1, 1) == "#")
 if !pos := regexmatch(ppmo, "\d+", pixel, pos)
    bitmap%A_Index% := pixel
    if (index == 4)
    pos := regexmatch(ppmo, "\s", x, pos)
    index ++
  type := bitmap1
  width := bitmap2
  height := bitmap3
  maxcolor := bitmap4
  bitmap := Bitmap(width, height, color(0,0,0))
  index := 1
  i := 1
  j := 1
 bits := pos 
loop % width * height 
      bitmap[i, j, "r"]  := numget(ppmo, 3 * A_Index + bits, "uchar")
      bitmap[i, j, "g"]  := numget(ppmo, 3 * A_Index + bits + 1, "uchar")
      bitmap[i, j, "b"]  := numget(ppmo, 3 * A_Index + bits + 2, "uchar")

      if (j == width)
	j := 1
	i += 1
 return bitmap  
#include bitmap_storage.ahk ; from
#include run.ahk ;


Works with: POSIX version .1-2001

Here I've used convert by ImageMagick. It is up to the program to understand the source file type; in this way, we can read theoretically any image format ImageMagick can handle. The get_ppm function defined in Read ppm file is used.

image read_image(const char *name);
#include "imglib.h"

#define MAXCMDBUF 100
image read_image(const char *name)
      FILE *pipe;
      char buf[MAXFULLCMDBUF];
      image im;
      FILE *test = fopen(name, "r");
      if ( test == NULL ) {
         fprintf(stderr, "cannot open file %s\n", name);
         return NULL;
      snprintf(buf, MAXFULLCMDBUF, "convert \"%s\" ppm:-", name);
      pipe = popen(buf, "r");
      if ( pipe != NULL )
           im = get_ppm(pipe);
           return im;
      return NULL;


This example uses convert to convert the test image for the flood fill task. It reads through the pipe as required for this task, then writes as a .ppm file convenient for the flood fill task.

package main

// Files required to build supporting package raster are found in:
// * Bitmap
// * Read a PPM file
// * Write a PPM file

import (

func main() {
    c := exec.Command("convert", "Unfilledcirc.png", "-depth", "1", "ppm:-")
    pipe, err := c.StdoutPipe()
    if err != nil {
    if err = c.Start(); err != nil {
    b, err := raster.ReadPpmFrom(pipe)
    if err != nil {
    if err = b.WritePpmFile("Unfilledcirc.ppm"); err != nil {


Works with: Julia version 0.6
using Images, FileIO

img = load("data/bitmapOutputTest.jpg")
save("data/bitmapOutputTest.ppm", img)


Works with: Ubuntu 16.04

The code for this is similar to that for the Bitmap/Read a PPM file task except that the .jpg file is converted via a pipe to .ppm format using the ImageMagick 'convert' tool and stored in a BasicBitmapStorage object. It is then converted to grayscale and saved back to disk as a .jpg file.

// Version 1.2.40

import java.awt.Color
import java.awt.Graphics
import java.awt.image.BufferedImage
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 =
        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 toGrayScale() {
        for (x in 0 until image.width) {
            for (y in 0 until image.height) {
                var rgb  = image.getRGB(x, y)
                val red   = (rgb shr 16) and 0xFF
                val green = (rgb shr  8) and 0xFF
                val blue  =  rgb and 0xFF
                val lumin = (0.2126 * red + 0.7152 * green + 0.0722 * blue).toInt()
                rgb = (lumin shl 16) or (lumin shl 8) or lumin
                image.setRGB(x, y, rgb)

fun PushbackInputStream.skipComment() {
    while (read().toChar() != '\n') {}

fun PushbackInputStream.skipComment(buffer: ByteArray) {
    var nl: Int
    while (true) {
        nl = buffer.indexOf(10) // look for newline at end of comment
        if (nl != -1) break
        read(buffer)  // read another buffer full if newline not yet found
    val len = buffer.size
    if (nl < len - 1) unread(buffer, nl + 1, len - nl - 1)

fun Byte.toUInt() = if (this < 0) 256 + this else this.toInt()

fun main(args: Array<String>) {
    // use file, output_piped.jpg, created in the
    // Bitmap/PPM conversion through a pipe task
    val pb = ProcessBuilder("convert", "output_piped.jpg", "ppm:-")
    val proc = pb.start()
    val pStdOut = proc.inputStream
    val pbis = PushbackInputStream(pStdOut, 80)
    pbis.use {
        with (it) {
            val h1 = read().toChar()
            val h2 = read().toChar()
            val h3 = read().toChar()
            if (h1 != 'P' || h2 != '6' || h3 != '\n') {
                println("Not a P6 PPM file")
            val sb = StringBuilder()
            while (true) {
                val r = read().toChar()
                if (r == '#') { skipComment(); continue }
                if (r == ' ') break  // read until space reached
            val width = sb.toString().toInt()
            while (true) {
                val r = read().toChar()
                if (r == '#') { skipComment(); continue }
                if (r == '\n') break  // read until new line reached
            val height = sb.toString().toInt()
            while (true) {
                val r = read().toChar()
                if (r == '#') { skipComment(); continue }
                if (r == '\n') break  // read until new line reached
            val maxCol = sb.toString().toInt()
            if (maxCol !in 0..255) {
                println("Maximum color value is outside the range 0..255")
            var buffer = ByteArray(80)
            // get rid of any more opening comments before reading data
            while (true) {
                if (buffer[0].toChar() == '#') {
                else {
            // read data
            val bbs = BasicBitmapStorage(width, height)
            buffer = ByteArray(width * 3)
            var y = 0
            while (y < height) {
                for (x in 0 until width) {
                    val c = Color(
                        buffer[x * 3].toUInt(),
                        buffer[x * 3 + 1].toUInt(),
                        buffer[x * 3 + 2].toUInt()
                    bbs.setPixel(x, y, c)
            // convert to grayscale and save to a file
            val grayFile = File("output_piped_gray.jpg")
            ImageIO.write(bbs.image, "jpg", grayFile)


Uses Bitmap class here, with an RGB tuple pixel representation, and the rudimentary PPM support here, and the Lenna image here.

First, the loadPPM() method is altered to allow passing an existing file handle:

function Bitmap:loadPPM(filename, fp)
  if not fp then fp =, "rb") end
  if not fp then return end
  local head, width, height, depth, tail = fp:read("*line", "*number", "*number", "*number", "*line")
  self.width, self.height = width, height
  for y = 1, self.height do
    for x = 1, self.width do
      self.pixels[y][x] = { string.byte(fp:read(1)), string.byte(fp:read(1)), string.byte(fp:read(1)) }

Then, for the actual "read-from-pipe" task, a Lua environment that supports io.popen() is required:

local bitmap = Bitmap(0,0)
fp = io.popen("magick Lenna100.jpg ppm:-", "rb")
bitmap:loadPPM(nil, fp)

bitmap:savePPM("Lenna100.ppm") -- just as "proof"

Mathematica/Wolfram Language

Based off the Julia program.



Using "jpegtopnm" from Netpbm suite. Input is a JPEG file and result (the PPM file) is sent to stdout. The procedure "readPPM" reads directly from the stream and build the image container.

import bitmap
import osproc
import ppm_read
import streams

# Launch Netpbm "jpegtopnm".
# Input is taken from "input.jpeg" and result sent to stdout.
let p = startProcess("jpegtopnm", args = ["input.jpeg"], options = {poUsePath})
let stream = FileStream(p.outputStream())
let image = stream.readPPM()
echo image.w, " ", image.h


The read_ppm function of the page read ppm file and used by the code below would need to be changed to take as parameter an input channel instead of the filename.

let read_image ~filename =
  if not(Sys.file_exists filename)
  then failwith(Printf.sprintf "the file %s does not exist" filename);
  let cmd = Printf.sprintf "convert \"%s\" ppm:-" filename in
  let ic, oc = Unix.open_process cmd in
  let img = read_ppm ~ic in


# 20211226 Perl programming solution

use strict;
use warnings;

use Imager;

my $raw;

open my $fh, '-|', 'cat Lenna50.jpg' or die;
binmode $fh;
while ( sysread $fh , my $chunk , 1024 ) { $raw .= $chunk }
close $fh;

my $enable = $Imager::formats{"jpeg"}; # some kind of tie ?

my $IO = Imager::io_new_buffer $raw or die;
my $im = Imager::File::JPEG::i_readjpeg_wiol $IO or die;

open my $fh2, '>', 'output.ppm' or die;
binmode $fh2;
my $IO2 = Imager::io_new_fd(fileno $fh2);
Imager::i_writeppm_wiol $im, $IO2 ;
close $fh2;
file output.ppm
output.ppm: Netpbm PPM "rawbits" image data, size = 512 x 512
magick identify output.ppm
output.ppm PPM 512x512 512x512+0+0 8-bit sRGB 786464B 0.000u 0:00.014


Uses the demo\rosetta\viewppm.exw utility to accomplish this task.
The returned data is raw binary, so you can either write it direct or chuck it through read_ppm/write_ppm.

-- demo\rosetta\Bitmap_Read_an_image_through_a_pipe.exw
without js -- file i/o, system_exec(), pipes[!!]
include builtins\pipeio.e
include ppm.e -- read_ppm(), write_ppm()

sequence pipes = repeat(0,3)
pipes[PIPOUT] = create_pipe(INHERIT_READ)

-- Create the child process, with replacement stdout. 
string cmd = sprintf("%s viewppm -load test.jpg",{get_interpreter(true)})
atom hProc = system_exec(cmd, 12, pipes),
     hPipe = pipes[PIPOUT][READ_PIPE]

string ppm = read_from_pipe(hPipe, hProc)
while true do
    object chunk = read_from_pipe(hPipe, hProc)
    if chunk=-1 then exit end if
    ppm &= chunk
end while

pipes = close_handles(pipes)

if 0 then
    sequence img = read_ppm(ppm,bText:=true)
    write_ppm("Lenapipe.ppm", img)
else -- or
    integer fn = open("Lenapipe.ppm","wb")
end if

{} = wait_key()


(setq *Ppm (ppmRead '("convert" "img.jpg" "ppm:-")))


Adapted from
Requires pillow-5.3.0 with Python 3.7.1 32-bit on Windows.
Sample ppm graphics files from

from PIL import Image

# boxes_1.jpg is the jpg version of boxes_1.ppm

im ="boxes_1.jpg")"boxes_1v2.ppm")

Does not need to pipe through a conversion utility because the Pillow module does the conversion.


(define (read-ppm port)
  (parameterize ([current-input-port port])
    (define magic (read-line))
    (match-define (list w h) (string-split (read-line) " "))
    (define width (string->number w))
    (define height (string->number h))
    (define maxcol (string->number (read-line)))
    (define bm (make-object bitmap% width height))
    (define dc (new bitmap-dc% [bitmap bm]))
    (send dc set-smoothing 'unsmoothed)
    (define (adjust v) (* 255 (/ v maxcol)))
    (for/list ([x width])
      (for/list ([y height])
        (define red (read-byte))
        (define green (read-byte))
        (define blue (read-byte))
        (define color (make-object color% (adjust red) (adjust green) (adjust blue)))
        (send dc set-pen color 1 'solid)
        (send dc draw-point x y)))

(define (image->bmp filename)
  (define command (format "convert ~a ppm:-" filename))
  (match-define (list in out pid err ctrl)  (process command))
  (define bmp (read-ppm in))
  (close-input-port in)
  (close-output-port out)

(image->bmp "input.jpg")


(formerly Perl 6)

Works with: Rakudo version 2017.09

Uses pieces from Bitmap and Read a PPM file tasks. Included here to make a complete, runnable program.

Uses imagemagick convert to pipe the image in.

class Pixel { has UInt ($.R, $.G, $.B) }
class Bitmap {
    has UInt ($.width, $.height);
    has Pixel;

role PPM {
    method P6 returns Blob {
	"P6\n{self.width} {self.height}\n255\n".encode('ascii')
	~ flat map { .R, .G, .B },

sub getline ( $proc ) {
    my $line = '#'; # skip comment when reading a .png
    $line = $proc.out.get while $line.substr(0,1) eq '#';

my $filename = './camelia.png';

my $proc = run 'convert', $filename, 'ppm:-', :enc('ISO-8859-1'), :out;

my $type = getline($proc);
my ($width, $height) = getline($proc).split: ' ';
my $depth = getline($proc);

my Bitmap $b = width => $width.Int, height => $height.Int) but PPM;

$ = $proc.out.slurp.ords.rotor(3).map:
  { => .[0], G => .[1], B => .[2]) };

'./camelia.ppm', :w).write: $b.P6;

See camelia image here.


Uses Raster graphics operations/Ruby.

# frozen_string_literal: true

require_relative 'raster_graphics'

class Pixmap
  def self.read_ppm(ios)
    format = ios.gets.chomp
    width, height =
    max_colour = ios.gets.chomp

    if !PIXMAP_FORMATS.include?(format) ||
       (width < 1) || (height < 1) ||
       (max_colour != '255')
      raise StandardError, "file '#{filename}' does not start with the expected header"
    ios.binmode if PIXMAP_BINARY_FORMATS.include?(format)

    bitmap = new(width, height)
    height.times do |y|
      width.times do |x|
        # read 3 bytes
        red, green, blue = case format
                           when 'P3' then ios.gets.chomp.split
                           when 'P6' then'C3')
        bitmap[x, y] =, green, blue)

    read_ppm(, 'r'))

  def self.open_from_jpeg(filename)
    read_ppm(IO.popen("convert jpg:#{filename} ppm:-", 'r'))

bitmap = Pixmap.open_from_jpeg('foto.jpg')'foto.ppm')


Works with: Tcl version 8.6
Library: Tk
package require Tk

proc magickalReadImage {bufferImage fileName} {
    set f [open |[list convert [file normalize $fileName] ppm:-] "rb"]
    try {
        $bufferImage put [read $f] -format ppm
    } finally {
        close $f


Library: DOME

As DOME doesn't have a method for calling an external process (ImageMagick in this case), we re-use the small plug-in ( we created in the 'PPM conversion through a pipe' task to add this functionality.

We can now use this plug-in in the following script which calls ImageMagick to convert the output_piped.jpg file to a ppm file so that we can load the latter, convert it to a gray scale image, display it and save it to a .jpg file.

import "graphics" for Canvas, ImageData, Color
import "dome" for Window, Process
import "io" for FileSystem
import "plugin" for Plugin


import "pipeconv" for PipeConv

class Bitmap {
    construct new(fileName, fileName2, fileName3, width, height) {
        Window.title = "Bitmap - read image via pipe"
        Window.resize(width, height)
        Canvas.resize(width, height)
        _w = width
        _h = height
        _fn3 = fileName3
        // convert .jpg file to .ppm via a pipe
        PipeConv.convert(fileName, fileName2)
        // load the .ppm file

    init() {
        // display gray scale image
        _bmp2.draw(0, 0)
        // save it to file

    loadPPMFile(fileName) {
        var ppm = FileSystem.load(fileName)
        var count = ppm.count //ensure file is fully loaded before proceeding 
        if (ppm[0..1] != "P6") {
            System.print("The loaded file is not a P6 file.")
        var lines = ppm.split("\n")
        if (Num.fromString(lines[2]) > 255) {
            System.print("The maximum color value can't exceed 255.")
        var wh = lines[1].split(" ")
        var w = Num.fromString(wh[0])
        var h = Num.fromString(wh[1])
        _bmp = ImageData.create(fileName, w, h)
        var bytes = ppm.bytes
        var i = bytes.count - 3 * w * h
        for (y in 0...h) {
            for (x in 0...w) {
                var r = bytes[i]
                var g = bytes[i+1]
                var b = bytes[i+2]
                var c = Color.rgb(r, g, b)
                pset(x, y, c)
                i = i + 3

    toGrayScale() {
        _bmp2 = ImageData.create("gray scale", _bmp.width, _bmp.height)
        for (x in 0..._bmp.width) {
            for (y in 0..._bmp.height) {
                var c1 = _bmp.pget(x, y)
                var lumin = (0.2126 * c1.r + 0.7152 * c1.g + 0.0722 * c1.b).floor
                var c2 = Color.rgb(lumin, lumin,lumin, c1.a)
                _bmp2.pset(x, y, c2)

    pset(x, y, col) { _bmp.pset(x, y, col) }

    pget(x, y) { _bmp.pget(x, y) }

    update() {}

    draw(alpha) {}

var Game ="output_piped.jpg", "output_piped.ppm", "output_piped_gs.jpg", 350, 350)


Translation of: C

Uses the PPM class from

Using the convert utility by ImageMagick:

p:=System.popen(0'|convert "fractalTree.jpg" ppm:-|,"r");
img:=PPM.readPPM(p); p.close();