PHP Unconference Europe 2015

imagecolorset

(PHP 4, PHP 5)

imagecolorsetSet the color for the specified palette index

Description

void imagecolorset ( resource $image , int $index , int $red , int $green , int $blue [, int $alpha = 0 ] )

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.

alpha

Value of alpha component.

Return Values

No value is returned.

Changelog

Version Description
5.4.0 The alpha parameter was added.

Examples

Example #1 imagecolorset() example

<?php
// Create a 300x100 image
$im imagecreate(300100);

// Set the background to be red
imagecolorallocate($im25500);

// Get the color index for the background
$bg imagecolorat($im00);

// Set the backgrund to be blue
imagecolorset($im$bg00255);

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

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

See Also

add a note add a note

User Contributed Notes 9 notes

up
1
olivier at moostik dot net
13 years ago
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;

}
up
0
Bartman
5 years ago
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']);
    }
}
?>
up
0
Thomas Mueller
6 years ago
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);
    }
}
?>
up
0
heavyraptor2 at hotmail dot com
6 years ago
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
up
0
admin at phpgfx dot com
7 years ago
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 );
    }
}

?>
up
0
moxleystratton.com
8 years ago
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);
    }
}
?>
up
0
dade dot c at email dot it
10 years ago
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);
}
up
0
m4551 at abasoft dot it
10 years ago
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);
    }
}
up
-1
info at devking dot com
12 years ago
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 );   
}
}
To Top