imagecolorset()

(PHP 4, PHP 5, PHP 7)

给指定调色板索引设定颜色

说明

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

本函数将调色板中指定的索引设定为指定的颜色。对于在调色板图像中创建类似区域填充（flood-fill）的效果很有用，免去了真的去填充的开销。

参见imagecolorat()。

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);
  }
}

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);
  }
}
?>

If you are creating a palette image from scratch you have to use imagecolorallocate() for each index before you can use imagecolorset() on it.

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);
  }
}
?>

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

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);
}

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;
 
 }

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']);
  }
}?>

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 );
  }
}
?>

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 );  
 }
}