Last updated: Fri, 27 Nov 2009

imagecolorset

(PHP 4, PHP 5)

imagecolorset — Set the color for the specified palette index

Description

void imagecolorset ( resource $image , int $index , int $red , int $green , int $blue )

This sets the specified index in the palette to the specified color. This is useful for creating flood-fill-like effects in palleted images without the overhead of performing the actual flood-fill.

Parameters

image: An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
index: An index in the palette.
red: Value of red component.
green: Value of green component.
blue: Value of blue component.

Return Values

No value is returned.

Examples

Example #1 imagecolorset() example


<?php
// Create a 300x100 image
$im = imagecreate(300, 100);

// Set the background to be red
imagecolorallocate($im, 255, 0, 0);

// Get the color index for the background
$bg = imagecolorat($im, 0, 0);

// Set the backgrund to be blue
imagecolorset($im, $bg, 0, 0, 255);

// Output the image to the browser
//header('Content-type: image/png');

imagepng($im);
imagedestroy($im);
?>


I had the same problem as heavyraptor2 so i made this function...

<?php

function imagecolorize($im,$endcolor){

    //funcion takes image and turns black into $endcolor, white to white and

    //everything in between in corresponding gradient

    //$endcolor should be 6 char html color



    //make sure it has usable palette

    if (imageistruecolor($im)) {

        imagetruecolortopalette($im, false, 256);

    }



    //first make it gray to be sure of even results (thanks moxleystratton.com)

    //comment this loop if you want the output based on, for example, 

    //the red channel (for this take a look at the $gray-var in the last loop)

    for ($c = 0; $c < imagecolorstotal($im); $c++) {

        $col = imagecolorsforindex($im, $c);

        $gray = round(0.299 * $col['red'] + 0.587 * $col['green'] + 0.114 * $col['blue']);

        imagecolorset($im, $c, $gray, $gray, $gray);

    }



    //determine end-colors in hexdec

    $EndcolorRGB['r'] = hexdec( substr($endcolor, 0, 2));

    $EndcolorRGB['g'] = hexdec( substr($endcolor, 2, 2));

    $EndcolorRGB['b'] = hexdec( substr($endcolor, 4, 2));



    //determine gradient-delta's

    $stepR = (255-$EndcolorRGB['r'])/255.0;

    $stepG = (255-$EndcolorRGB['g'])/255.0;

    $stepB = (255-$EndcolorRGB['b'])/255.0;



    //aColor contains the 256 gradations between endcolor(i=0) and white(i=255)

    $aColor = array();

    for ($i = 0; $i<=255; $i++){

        $aColor[$i]['r'] = $EndcolorRGB['r'] + ($i*$stepR);

        $aColor[$i]['g'] = $EndcolorRGB['g'] + ($i*$stepG);

        $aColor[$i]['b'] = $EndcolorRGB['b'] + ($i*$stepB);

    }



    //for every color-index we now replace $gray-values for $aColor

    for ($c = 0; $c < imagecolorstotal($im); $c++){

        $currentColorRGB = imagecolorsforindex($im, $c);

        $gray = $currentColorRGB['red'];//image is grayscale, so red,green and blue

        // should be equal. We use this number as key of aColor

        imagecolorset($im,$c,(int)$aColor[$gray]['r'], (int)$aColor[$gray]['g'], (int)$aColor[$gray]['b']);

    }

}?>

Thomas Mueller
23-Apr-2008 05:42


Here is a function to colorize a picture gradient style.



All you have to do is to pass an img-object and an array of colors.



e.g.



$arr = array('#000000', '#990000', '#00FFFF', '#FFFFDD');

colorize ($img, $arr);



<?php

function colorize($imgdata, $palette)

{

    imageTrueColorToPalette($imgdata,false,0xFF);

    $l = count($palette)-1;

    $i = imagecolorstotal($imgdata);

    while ($i--)

    {

        list($r,$g,$b) = array_values(imageColorsForIndex($imgdata,$i));

        

        $grayscale = ($r*.3 + $g*.59 +$b*.11) / 0xFF;

        

        $pos = $l*$grayscale;

        

        $perc = $pos-floor($pos);

        

        $tbase = str_replace("#", '', $palette[$pos]);

        $baseR = hexdec(substr($tbase,0,2));

        $baseG = hexdec(substr($tbase,2,2));

        $baseB = hexdec(substr($tbase,4,2));

        

        $tmix = str_replace("#", '', $palette[$pos+1]);

        $mixR = hexdec(substr($tmix,0,2));

        $mixG = hexdec(substr($tmix,2,2));

        $mixB = hexdec(substr($tmix,4,2));

        

        $resR = $baseR+($mixR-$baseR)*$perc;

        $resG = $baseG+($mixG-$baseG)*$perc;

        $resB = $baseB+($mixB-$baseB)*$perc;

        

        imagecolorset($imgdata, $i, $resR, $resG, $resB);

    }

}

?>

heavyraptor2 at hotmail dot com
20-Feb-2008 09:08


I've been looking for a simple function which "colorizes" an image, without any success ... it looks like a lot of people mean something different with "colorizing" an image, because actually colorzing means multiplying the old color's grayscale with the new color. So a white pixel would become 100% of the colorize-to-color and a black pixel would stay black (I know I can't explain well ... I hope you understood, otherwise take a look at the example below the functions' code).



<?php

function image_colorize(&$img,$rgb) {

  imageTrueColorToPalette($img,true,256);

  $numColors = imageColorsTotal($img);



  for ($x = 0; $x < $numColors; $x++) {

    list($r,$g,$b) = array_values(imageColorsForIndex($img,$x));



    // calculate grayscale in percent

    $grayscale = ($r + $g + $b) / 3 / 0xff;



    imageColorSet($img,$x,

      $grayscale * $rgb[0],

      $grayscale * $rgb[1],

      $grayscale * $rgb[2]

    );

  }



  return true;

}

?>



Example of usage:

<?php

$color = array(0xff,0xaa,0x2a); // color to convert to

$url = 'http://sundog.net/images/uploads/1_google_logo.jpg';

$img = imageCreateFromJpeg($url);



image_colorize($img,$color);



header('Content-type: image/gif');

imageGif($img);

exit;

?>



Enjoy

admin at phpgfx dot com
25-Aug-2007 06:37


Here is a function to turn an image into pure black and white



<?php



function imagepurebw( $img, $amount = 383 ) {

    $total = imagecolorstotal( $img );

    for ( $i = 0; $i < $total; $i++ ) {

        $index = imagecolorsforindex( $img, $i );

        array_pop( $index );

        $color = ( array_sum( $index ) > $amount ) ? 255 : 0;

        imagecolorset( $img, $i, $color, $color, $color );

    }

}



?>

moxleystratton.com
04-Oct-2006 10:59


If you want to convert a Color image to Grayscale without creating a blotchy image, use this color calculation:

<?php

function imagetograyscale($im)

{

    if (imageistruecolor($im)) {

        imagetruecolortopalette($im, false, 256);

    }



    for ($c = 0; $c < imagecolorstotal($im); $c++) {

        $col = imagecolorsforindex($im, $c);

        $gray = round(0.299 * $col['red'] + 0.587 * $col['green'] + 0.114 * $col['blue']);

        imagecolorset($im, $c, $gray, $gray, $gray);

    }

}

?>

dade dot c at email dot it
02-Oct-2004 08:47


this is helpful if you would like to implement a color theme system in your website... try it out

Davide Candiloro Italy



function colorize ($pngpath, $r, $g, $b) 

/*

REQUIRES: $pngpath to be a valid path of a greyscale PNG-8 image with 64 colors palette

          $r, $g, $b to be integers in the range 0..255

EFFECTS: returns the png image colorized with the color represented by $r, $g, $b.

*/

{

    header("Content-type: image/png");

    $im = imagecreatefrompng("images/table.png");



    imagetruecolortopalette($im, FALSE, 256); 

   

      for ($c = 0; $c < 64; $c++){ /*64 is the number of colors in the PNG-8 palette*/

        $col = imagecolorsforindex($im, $c);           

        imagecolorset ( $im, $c, $r*$col['red']/256, $g*$col['green']/256, $b*$col['blue']/256); /*replaces original greyscale palette with a colorized one*/

     }



    imagepng($im);

    imagedestroy($im);

}

m4551 at abasoft dot it
23-Apr-2004 04:19


here's a function to greyscale an image even from a truecolor source (jpeg or png).



slightly poor quality, but very fast...



function imagegreyscale(&$img, $dither=1) {    

    if (!($t = imagecolorstotal($img))) {

        $t = 256;

        imagetruecolortopalette($img, $dither, $t);    

    }

    for ($c = 0; $c < $t; $c++) {    

        $col = imagecolorsforindex($img, $c);

        $min = min($col['red'],$col['green'],$col['blue']);

        $max = max($col['red'],$col['green'],$col['blue']);

        $i = ($max+$min)/2;

        imagecolorset($img, $c, $i, $i, $i);

    }

}

info at devking dot com
08-Aug-2002 09:20


here's a simple function to greyscale an image...



function imagecolorgrey( &$img ) {

 for( $i=0; $i<imagecolorstotal( $img ); $i++ ) {

  $c = ImageColorsForIndex( $img, $i );

  $t = ($c["red"]+$c["green"]+$c["blue"])/3;

  imagecolorset( $img, $i, $t, $t, $t );    

 }

}

olivier at moostik dot net
12-Jul-2001 12:49


This function change colors of an image with ranges 0>100 for each primary color:





int ImageSelectiveColor (int im, int red, int green, int blue)





im is image pointer


red, green and blue are ranges 0->100





function ImageSelectiveColor($im,$red,$green,$blue)


 {


  for($i=0;$i<imagecolorstotal($im);$i++)


   {


    $col=ImageColorsForIndex($im,$i);


    $red_set=$red/100*$col['red'];


    $green_set=$green/100*$col['green'];


    $blue_set=$blue/100*$col['blue'];


    if($red_set>255)$red_set=255;


    if($green_set>255)$green_set=255;


    if($blue_set>255)$blue_set=255;


    imagecolorset($im,$i,$red_set,$green_set,$blue_set);


    


   }


  return $im;


 


 }

add a note

imagecolorsforindex

imagecolorresolvealpha