PHP Australia Conference 2015

imagecolorallocate

(PHP 4, PHP 5)

imagecolorallocateAllocate a color for an image

Descrizione

int imagecolorallocate ( resource $image , int $red , int $green , int $blue )

Returns a color identifier representing the color composed of the given RGB components.

imagecolorallocate() must be called to create each color that is to be used in the image represented by image.

Nota:

The first call to imagecolorallocate() fills the background color in palette-based images - images created using imagecreate().

Elenco dei parametri

image

Una risorsa immagine, restituita da una delle funzioni di creazione immagine, come imagecreatetruecolor().

red

Valore della componente rossa.

green

Valore della componente verde.

blue

Valore della componente blu.

These parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.

Valori restituiti

A color identifier or FALSE if the allocation failed.

Avviso

Questa funzione può restituire il Booleano FALSE, ma può anche restituire un valore non-Booleano valutato come FALSE. Fare riferimento alla sezione Booleans per maggiori informazioni. Usare l'operatore === per controllare il valore restituito da questa funzione.

Log delle modifiche

Versione Descrizione
5.1.3 Returns FALSE if the allocation failed. Previously -1 was returned.

Esempi

Example #1 imagecolorallocate() example

<?php

$im 
imagecreate(100100);

// sets background to red
$background imagecolorallocate($im25500);

// sets some colors
$white imagecolorallocate($im255255255);
$black imagecolorallocate($im000);

// hexadecimal way
$white imagecolorallocate($im0xFF0xFF0xFF);
$black imagecolorallocate($im0x000x000x00);

?>

Vedere anche:

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User Contributed Notes 21 notes

up
10
Ludo
6 years ago
When working on an existant GIF images, if the number of different colours has reached the limits of the GIF format, imagecolorallocate will not use to the colour you ask her within the parameters, she will apply black !

That's a problem when generating images "on-the-fly" with many manipulations, from a GIF image.
To go round the problem, you have to convert the GIF image into a PNG one, and then you can work on the PNG and everything will be ok.

For example :
<?php
// first, convert into a PNG image
$handle = imagecreatefromgif('my_image.gif');
imagepng($handle, 'my_image.png');
imagedestroy($handle);

// then, you can work on it
$handle = imagecreatefrompng('my_image.png');
/*
* work on the image
*/
imagegif($handle);
?>
up
3
phillip dot gooch at gmail dot com
3 years ago
If you even in a situation where it's not allocating the color you want it could be because of your images color allocation table. GIF and 8-bit PNG images are very susceptible to this.

If your using an GIF and PNG try dropping a color from the table, should let you allocate another.
up
4
SW
8 years ago
This works! A Black-Image with vertical centered white Aliased Arial-Text and same left and right margin - used for Menu-Buttons.

<?php

 
function createImgText ($string="", $fontsize=0, $marginX=0, $imgH=0 , $fontfile="", $imgColorHex="", $txtColorHex=""){
    if(
$string!=""){
       
Header("Content-type: image/png");    
       
//
       
$spacing = 0;
         
$line = array("linespacing" => $spacing);
       
$box = @imageftbbox($fontsize,0,$fontfile,$string,$line)
        or die(
"ERROR");
       
$tw=$box[4]-$box[0]; //image width
       
$marginY = $imgH - (($imgH - $fontsize) / 2);
       
$imgWidth = $tw + (2*$marginX);
       
$im = ImageCreate($imgWidth, $imgH);
       
$int = hexdec($imgColorHex);
       
$arr = array("red" => 0xFF & ($int >> 0x10),
              
"green" => 0xFF & ($int >> 0x8),
              
"blue" => 0xFF & $int);
       
$black = ImageColorAllocate($im, $arr["red"], $arr["green"], $arr["blue"]);
       
$int = hexdec($txtColorHex);
       
$arr = array("red" => 0xFF & ($int >> 0x10),
              
"green" => 0xFF & ($int >> 0x8),
              
"blue" => 0xFF & $int);
       
$white = ImageColorAllocate($im, $arr["red"], $arr["green"], $arr["blue"]);
       
ImageFtText($im, $fontsize, 0, $marginX, $marginY, $white, $fontfile, $string, array());
       
ImagePng($im);
       
ImageDestroy($im);
    }else{
        echo
"ERROR!";
    }
}
createImgText ("Hello World", 9, 10, 18, "arial.ttf", "000000", "FFFFFF");
?>
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3
jahservant 13 at gmail dot com
4 years ago
Note that you can only assign 255 colors to any image palette.  If you try assigning more, imagecolorallocate() will fail.

If, for example, you are randomly allocating colors, it will be wise to check if you have used up all of the colors possible.  You can use imagecolorclosest() to get the closest assigned color:
<?php
    
//assign random rgb values
    
$c1 = mt_rand(50,200); //r(ed)
    
$c2 = mt_rand(50,200); //g(reen)
    
$c3 = mt_rand(50,200); //b(lue)
     //test if we have used up palette
    
if(imagecolorstotal($pic)>=255) {
         
//palette used up; pick closest assigned color
         
$color = imagecolorclosest($pic, $c1, $c2, $c3);
     } else {
         
//palette NOT used up; assign new color
         
$color = imagecolorallocate($pic, $c1, $c2, $c3);
     }
?>

Also, imagecolorallocate() will assign a new color EVERY time the function is called, even if the color already exists in the palette:
<?php
    
// [...]
    
imagecolorallocate($pic,125,125,125); //returns 5
    
imagecolorallocate($pic,125,125,125); //returns 6
    
imagecolorallocate($pic,125,125,125); //returns 7
     // [...]
    
imagecolorallocate($pic,125,125,125); //returns 23
    
imagecolorallocate($pic,125,125,125); //returns 25
     // [...]
     // etc...
?>

So here, imagecolorexact() is useful:
<?php
    
//see if color already exists
    
$color = imagecolorexact($pic, $c1, $c2, $c3);
     if(
$color==-1) {
         
//color does not exist; allocate a new one
         
$color = imagecolorallocate($pic, $c1, $c2, $c3);
     }
?>

And, for nerdy-ness sake, we can put the two ideas together:
<?php
    
//assign random rgb values
    
$c1 = mt_rand(50,200); //r(ed)
    
$c2 = mt_rand(50,200); //g(reen)
    
$c3 = mt_rand(50,200); //b(lue)
     //get color from palette
    
$color = imagecolorexact($pic, $c1, $c2, $c3);
     if(
$color==-1) {
         
//color does not exist...
          //test if we have used up palette
         
if(imagecolorstotal($pic)>=255) {
              
//palette used up; pick closest assigned color
              
$color = imagecolorclosest($pic, $c1, $c2, $c3);
          } else {
              
//palette NOT used up; assign new color
              
$color = imagecolorallocate($pic, $c1, $c2, $c3);
          }
     }
?>

Or as a function:
<?php
    
function createcolor($pic,$c1,$c2,$c3) {
         
//get color from palette
         
$color = imagecolorexact($pic, $c1, $c2, $c3);
          if(
$color==-1) {
              
//color does not exist...
               //test if we have used up palette
              
if(imagecolorstotal($pic)>=255) {
                   
//palette used up; pick closest assigned color
                   
$color = imagecolorclosest($pic, $c1, $c2, $c3);
               } else {
                   
//palette NOT used up; assign new color
                   
$color = imagecolorallocate($pic, $c1, $c2, $c3);
               }
          }
          return
$color;
     }

     for(
$i=0; $i<1000; $i++) { //1000 because it is significantly greater than 255
          //assign random rgb values
         
$c1 = mt_rand(50,200); //r(ed)
         
$c2 = mt_rand(50,200); //g(reen)
         
$c3 = mt_rand(50,200); //b(lue)
          //generate the color
         
$color = createcolor($pic,$c1,$c2,$c3);
         
//do something with color...
    
}
?>
up
1
William Barath
7 years ago
Lots of hsv2rgb commentary but no working example, so here's mine:

<?php // hsv2rgb example translated from ImageMagick C code
function hsv2rgb($h, $s, $v)
{
   
$s /= 256.0;
    if (
$s == 0.0) return array($v,$v,$v);
   
$h /= (256.0 / 6.0);
   
$i = floor($h);
   
$f = $h - $i;
   
$p = (integer)($v * (1.0 - $s));
   
$q = (integer)($v * (1.0 - $s * $f));
   
$t = (integer)($v * (1.0 - $s * (1.0 - $f)));
    switch(
$i) {
    case
0: return array($v,$t,$p);
    case
1: return array($q,$v,$p);
    case
2: return array($p,$v,$t);
    case
3: return array($p,$q,$v);
    case
4: return array($t,$p,$v);
    default: return array(
$v,$p,$q);
    }
}

$image = ImageCreateTrueColor(256,128);
for (
$y=0; $y<64; $y++) for($x=0; $x<256; $x++){
    list(
$r,$g,$b) = hsv2rgb($x | 7,255,($y*4) |7);
   
$color = ($r << 16 ) | ($g << 8) | $b;
   
imagesetpixel($image, $x, $y-4, $color);
}
for (
$y=64; $y<128; $y++) for($x=0; $x<256; $x++){
    list(
$r,$g,$b) = hsv2rgb($x|7,((127-$y)*4)|7,255);
   
$color = ($r << 16) | ($g << 8) | $b;
   
imagesetpixel($image, $x, $y-4, $color);
}
for (
$y=120; $y<128; $y++) for($x=0; $x<256; $x++){
   
$color = (($x |7) << 16) | (($x |7) << 8) | ($x |7);
   
imagesetpixel($image, $x, $y, $color);
}
header("Content-Type: image/png");
imagepng($image);
?>
up
1
picklecj at rose-hulman dot edu
7 years ago
Another solution to color limitation issues when creating gradients. This file takes width (px) and left and right colors (hex) and makes a gradient while only allocating 250 colors.

<?php
$leftR
= hexdec(substr($_GET["left"],0,2));
$leftG = hexdec(substr($_GET["left"],2,2));
$leftB = hexdec(substr($_GET["left"],4,2));
$rightR = hexdec(substr($_GET["right"],0,2));
$rightG = hexdec(substr($_GET["right"],2,2));
$rightB = hexdec(substr($_GET["right"],4,2));
$image=imagecreate($_GET["width"],1);
for(
$i=0;$i<250;$i++) {
   
$colorset[$i] = imagecolorallocate($image, $leftR + ($i*(($rightR-$leftR)/250)), $leftG + ($i*(($rightG-$leftG)/250)), $leftB + ($i*(($rightB-$leftB)/250)));
}
for(
$i=0;$i<($_GET["width"]);$i++) {
 
imagesetpixel ($image, $i, 0, $colorset[(int)($i/($_GET["width"]/250))] );
}
header("Content-type: image/png");
imagepng($image);
imagedestroy($image);
?>

example: gradient.php?width=640&left=000000&right=FF0000

Makes a 640px-wide image that fades from black to red.
up
1
tyberis
9 years ago
2 functions to convert from HSV colorspace (hue/saturation/brightness) to RGB (red/green/blue) colorspace and back.
<?php
// $c = array($red, $green, $blue)
// $red=[0..1], $green=[0..1], $blue=[0..1];
function rgb2hsv($c) {
list(
$r,$g,$b)=$c;
$v=max($r,$g,$b);
$t=min($r,$g,$b);
$s=($v==0)?0:($v-$t)/$v;
if (
$s==0)
 
$h=-1;
else {
 
$a=$v-$t;
 
$cr=($v-$r)/$a;
 
$cg=($v-$g)/$a;
 
$cb=($v-$b)/$a;
 
$h=($r==$v)?$cb-$cg:(($g==$v)?2+$cr-$cb:(($b==$v)?$h=4+$cg-$cr:0));
 
$h=60*$h;
 
$h=($h<0)?$h+360:$h;
}
return array(
$h,$s,$v);
}

// $c = array($hue, $saturation, $brightness)
// $hue=[0..360], $saturation=[0..1], $brightness=[0..1]
function hsv2rgb($c) {
list(
$h,$s,$v)=$c;
if (
$s==0)
  return array(
$v,$v,$v);
else {
 
$h=($h%=360)/60;
 
$i=floor($h);
 
$f=$h-$i;
 
$q[0]=$q[1]=$v*(1-$s);
 
$q[2]=$v*(1-$s*(1-$f));
 
$q[3]=$q[4]=$v;
 
$q[5]=$v*(1-$s*$f);
 
//return(array($q[($i+4)%5],$q[($i+2)%5],$q[$i%5]));
 
return(array($q[($i+4)%6],$q[($i+2)%6],$q[$i%6])); //[1]
}
}
?>

[1] - EDITOR NOTE: THIS IS A FIX FROM "hc at hob(removethis)soft dot net".
up
1
bisqwit at iki dot fi
12 years ago
Actually, you can't allocate more than 256 colours for an paletted image (ImageCreate).
Use ImageCreateTrueColor instead. For it to work, you need libgd version 2 support in php though.
up
0
behun at webconsult dot sk
8 years ago
Also, when you need more then 256 colors, use imagecreatetruecolor function. With this function you can use unlimited number of colors.
up
0
mlse
8 years ago
Another more general variation on the theme using the same naming conventions as the hexdec and dechex built-in functions ...

Prototype:

array hexrgb ( string hex_string )

Returns:

An associative array of the RGB components specified in hex_string.

hexrgb() example:

<?php
$rgb
= hexrgb("0xAABBCC");
print_r($rgb);
?>

Output is:

Array
(
  [red] => 170
  [green] => 187
  [blue] => 204
)

Implementation:

<?php
function hexrgb ($hexstr)
{
 
$int = hexdec($hexstr);

  return array(
"red" => 0xFF & ($int >> 0x10),
              
"green" => 0xFF & ($int >> 0x8),
              
"blue" => 0xFF & $int);
}
?>

The output of hexdec can then be passed to imagecolorallocate and manipulated as required.
up
0
Zigbigidorlu at hotmail dot com
8 years ago
Here's a very simple and very effective code to change a HEX color to RGB.

<?php
function HEX2RGB($color){
$color_array = array();
$hex_color = strtoupper($color);
for(
$i = 0; $i < 6; $i++){
 
$hex = substr($hex_color,$i,1);
  switch(
$hex){
   case
"A": $num = 10; break;
   case
"B": $num = 11; break;
   case
"C": $num = 12; break;
   case
"D": $num = 13; break;
   case
"E": $num = 14; break;
   case
"F": $num = 15; break;
   default:
$num = $hex; break;
  }
 
array_push($color_array,$num);
}
$R = (($color_array[0] * 16) + $color_array[1]);
$G = (($color_array[2] * 16) + $color_array[3]);
$B = (($color_array[4] * 16) + $color_array[5]);
return array(
$R,$G,$B);
unset(
$color_array,$hex,$R,$G,$B);
}
?>
up
0
mail at kailashnadh dot name
9 years ago
This nifty function will produce the negative of a given image!

<?php

/********************************

     Code by Kailash Nadh
     http://kailashnadh.name

     usage:
     img2neg("my_pic.jpg");

*********************************/

function img2neg($pic) {

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

   
$source=imagecreatefromjpeg($pic);    // Source
   
$width=imagesx($source);    $height=imagesy($source);

   
$im = imagecreatetruecolor($width, $height);    // Our negative img in the making

   
for($y=0; $y < $height; $y++) {
        for(
$x=0; $x < $width; $x++) {

       
$colors=imagecolorsforindex($source, imagecolorat($source, $x,$y));

           
// this is what makes the colors negative
           
$r=255-$colors['red'];
           
$g=255-$colors['green'];
           
$b=255-$colors['blue'];
           
$test=imagecolorallocate($im, $r,$g,$b);
           
imagesetpixel($im,$x, $y, $test);
        }
    }

   
imagejpeg($im);
   
imagedestroy($im);
}

?>
up
0
andreoli dot carlo at libero dot it
9 years ago
hsl to RGB
(not yet optimized but it function)

<?php
function hslToRgb ($h, $s, $l) {
    if (
$h>240 || $h<0) return array(0,0,0);
    if (
$s>240 || $s<0) return array(0,0,0);
    if (
$l>240 || $l<0) return array(0,0,0);    
    if (
$h<=40) {
       
$R=255;
       
$G=(int)($h/40*256);
       
$B=0;
    }
    elseif (
$h>40 && $h<=80) {
       
$R=(1-($h-40)/40)*256;
       
$G=255;
       
$B=0;
    }
    elseif (
$h>80 && $h<=120) {
       
$R=0;
       
$G=255;
       
$B=($h-80)/40*256;
    }
    elseif (
$h>120 && $h<=160) {
       
$R=0;
       
$G=(1-($h-120)/40)*256;
       
$B=255;
    }
    elseif (
$h>160 && $h<=200) {
       
$R=($h-160)/40*256;
       
$G=0;
       
$B=255;
    }
    elseif (
$h>200) {
       
$R=255;
       
$G=0;
       
$B=(1-($h-200)/40)*256;
    }
   
$R=$R+(240-$s)/240*(128-$R);
   
$G=$G+(240-$s)/240*(128-$G);
   
$B=$B+(240-$s)/240*(128-$B);
    if (
$l<120) {
       
$R=($R/120)*$l;
       
$G=($G/120)*$l;
       
$B=($B/120)*$l;
    }
    else {
       
$R=$l*((256-$R)/120)+2*$R-256;
       
$G=$l*((256-$G)/120)+2*$G-256;
       
$B=$l*((256-$B)/120)+2*$B-256;
    }
    if (
$R<0) $R=0;
    if (
$R>255) $R=255;
    if (
$G<0) $G=0;
    if (
$G>255) $G=255;
    if (
$B<0) $B=0;
    if (
$B>255) $B=255;
   
    return array((int)
$R,(int)$G,(int)$B);
}
?>
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0
mv at brazil dot com
9 years ago
<?php

/**
* Create a image bar using lib GD
* Ege. <img src="color_sample.php?color=FF0000" width="10 height="30">
*/

// Split the HTML color representation
$hexcolor = str_split($_GET["color"], 2);

// Convert HEX values to DECIMAL
$bincolor[0] = hexdec("0x{$hexcolor[0]}");
$bincolor[1] = hexdec("0x{$hexcolor[1]}");
$bincolor[2] = hexdec("0x{$hexcolor[2]}");

$im = ImageCreate(100, 100);
$colorallocate = ImageColorAllocate($im, $bincolor[0], $bincolor[1], $bincolor[2]);
ImageFilledRectangle($im, 0, 0, 100, 100, $colorallocate);
header('Content-Type: image/png');
ImagePNG($im);

?>
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0
Anonymous
9 years ago
When you are using truecolor images, you can also use bitwise operations to generate the color:
<?php
$color
= ($r << 16) | ($g << 8) | $b; // 2261213
?>
This is identical to the imagecolorallocate() function, in truecolor images!
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0
aaron at parecki dot com
9 years ago
This will let you tint an image to any specific color. The blacks of the source image become your specified color, and the whites remain white. Works best for colorizing greyscale images.

<?php

$r
= 224;
$g = 192;
$b = 0;
$source_file = "picture.jpg";

$im_src = ImageCreateFromJpeg($source_file);
$im_tint = ImageCreate(imagesx($im_src),imagesy($im_src));
for (
$c = 0; $c < 255; $c++) {
    
ImageColorAllocate($im_tint, max($r,$c), max($g,$c), max($b,$c));
}
ImageCopyMerge($im_tint,$im_src,0,0,0,0, imagesx($im_src), imagesy($im_src), 100);
ImageDestroy($im_src);

header("Content-type: image/jpeg");
imagejpeg($im_tint);

?>
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0
smoli at paranoya dot ch
10 years ago
Some of you maybe want to use HSV color model for drawing color selectors and circles:

<?php
 
function &colormap_hsv_to_rgb($h, $s, $v)
  {
   
$ret = new stdClass();

    if(
$s == 0)
    {
     
$ret->r = $v;
     
$ret->g = $v;
     
$ret->b = $v;

      return
$ret;
    }
    else
    {
     
$h = floatval($h) / 255.0;
     
$s = floatval($s) / 255.0;
     
$v = floatval($v) / 255.0;

     
$hue = $h;

      if(
$hue == 1.0)
       
$hue = 0.0;

     
$hue *= 6.0;

     
$i = intval($hue);
     
$f = $hue - floatval($i);
     
$w = $v * (1.0 - $s);
     
$q = $v * (1.0 - ($s * $f));
     
$t = $v * (1.0 - ($s * (1.0 - $f)));

      switch(
$i)
      {
         case
0: $ret->r = $v; $ret->g = $t; $ret->b = $w; break;
         case
1: $ret->r = $q; $ret->g = $v; $ret->b = $w; break;
         case
2: $ret->r = $w; $ret->g = $v; $ret->b = $t; break;
         case
3: $ret->r = $w; $ret->g = $q; $ret->b = $v; break;
         case
4: $ret->r = $t; $ret->g = $w; $ret->b = $v; break;
         case
5: $ret->r = $v; $ret->g = $w; $ret->b = $q; break;
      }
    }
   
   
$ret->r = intval($ret->r * 255.0);
   
$ret->g = intval($ret->g * 255.0);
   
$ret->b = intval($ret->b * 255.0);

    return
$ret;
  }
?>
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jernberg at fairytale dot se
10 years ago
this might help someone, how to allocate an color from an html color-definition:

<?php
$fg
= "#ff0080";

$red = 100;
$green = 100;
$blue = 100;
if(
eregi( "[#]?([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})", $fg, $ret ) )
{
   
$red = hexdec( $ret[1] );
   
$green = hexdec( $ret[2] );
   
$blue = hexdec( $ret[3] );
}

$text_color = ImageColorAllocate( $img1, $red, $green, $blue );
?>
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chris at drunkenpirates dot co dot uk
11 years ago
<?php

/*
An example combining the use of ImageColorAllocate, Imagesetpixel, Imagecopyresized and some basic Trig
*/

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

$height = 128;
$width = 128;

$imA = ImageCreate($width, $height);
$imB = ImageCreate($width*4, $height*4);
$bckA = ImageColorAllocate($imA, 0,0,0);
$bckB = ImageColorAllocate($imB, 0,0,0);

//GENERATE GRAY SCALE PALLETE

for($c=0;$c<256;$c++){
               
ImageColorAllocate($imA, $c, $c, $c);
                }

//PRODUCE DATA

$m=rand(0,10);
for(
$c=0;$c<128;$c++){
               
$s=  (sin( deg2rad($c*360*$m/128) )+1)*127;
               
$col_arr[$c]=$s;
                }
for(
$y=0;$y<$height;$y++){
        for(
$x=0;$x<$width;$x++){
               
$imgA[$x][$y]=$col_arr[$x];
                }
        }
for(
$y=0;$y<$height;$y++){
        for(
$x=0;$x<$width;$x++){
               
$imgB[$x][$y]=$col_arr[$y];
                }
        }

//SET PIXELS

for($y=0;$y<$height;$y++){
        for(
$x=0;$x<$width;$x++){
               
$imgC[$x][$y]=$imgA[$x][$y]+$imgB[$x][$y];
               
$s=$imgC[$x][$y]/2;
               
Imagesetpixel($imA,$x,$y,$s);
                }
        }

//RESIZE IMAGE FOR DISPLAY

Imagecopyresized ($imB, $imA, 0, 0, 0, 0, $width*4, $height*4, $width, $width);
ImagePNG($imB);
?>
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leif at harmsen dot net
11 years ago
I was unable to get any of the posted methods for converting colour to grayscale to work.  The problem appears to be the way gd creates images from jpeg inconsistently over various versions.  Eventually I wrote my own that works for me - this approach allocates the 256 color pallete first.  You can also play with separate $r, $g, $b variables before using imagecolorallocate in order to tone or tint the image.

<?php
$resource
= 'whatever.jpg';
$im_size = GetImageSize($resource);
$imageWidth = $im_size[0];
$imageHeight = $im_size[1];
$im = imageCreate($imageWidth,$imageHeight);
for (
$c = 0; $c < 256; $c++) {    
    
ImageColorAllocate($im, $c,$c,$c);
}
$im2 = ImageCreateFromJpeg($resource);
ImageCopyMerge($im,$im2,0,0,0,0, $imageWidth, $imageHeight, 100);
ImageDestroy($im2);
?>

go on using $im as your image, it is now grayscale ....
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jasper at pointless dot net
11 years ago
a patch to php 4.3.0 to add imagecolorallocatealpha is here:

http://pointless.net/~jasper/php-4.3.0-imagecolorallocatealpha.patch

cd php-4.3.0/ext/gd
patch < path/to/patch

and recompile and reinstall.
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