Imagick::setImageColorspace()

(PECL imagick 2.0.0)

Sets the image colorspace

说明

Imagick::setImageColorspace(int $colorspace): bool

Sets the image colorspace. This method should be used when creating new images. To change the colorspace of an existing image, you should use Imagick::transformImageColorspace().

参数

$colorspace

One of the COLORSPACE constants

返回值

成功时返回TRUE。

错误／异常

错误时抛出 ImagickException。

When converting from CMYK to RGB using this function, the image can become inverted. To fix this, use a workaround (don't forget to download the .icc files online): 
<?php 
// don't use this (it inverts the image) 
//  $img->setImageColorspace (imagick::COLORSPACE_RGB); 
if ($img->getImageColorspace() == Imagick::COLORSPACE_CMYK) { 
  $profiles = $img->getImageProfiles('*', false); 
  // we're only interested if ICC profile(s) exist 
  $has_icc_profile = (array_search('icc', $profiles) !== false); 
  // if it doesnt have a CMYK ICC profile, we add one 
  if ($has_icc_profile === false) { 
    $icc_cmyk = file_get_contents(dirname(__FILE__).'/USWebUncoated.icc'); 
    $img->profileImage('icc', $icc_cmyk); 
    unset($icc_cmyk); 
  } 
  // then we add an RGB profile 
  $icc_rgb = file_get_contents(dirname(__FILE__).'/sRGB_v4_ICC_preference.icc'); 
  $img->profileImage('icc', $icc_rgb); 
  unset($icc_rgb); 
} 
$img->stripImage (); // this will drop down the size of the image dramatically (removes all profiles) 
?>

FYI, here is the breakdown for (int $colorspace):
Constants:
0 - UndefinedColorspace  
1 - RGBColorspace  
2 - GRAYColorspace  
3 - TransparentColorspace  
4 - OHTAColorspace  
5 - LABColorspace  
6 - XYZColorspace  
7 - YCbCrColorspace  
8 - YCCColorspace  
9 - YIQColorspace  
10 - YPbPrColorspace  
11 - YUVColorspace  
12 - CMYKColorspace  
13 - sRGBColorspace  
14 - HSBColorspace  
15 - HSLColorspace  
16 - HWBColorspace

Simlest way converting from CMYK to RGB:
<?php
if ($jpeg->getImageColorspace() == \Imagick::COLORSPACE_CMYK) {
  $jpeg->transformimagecolorspace(\Imagick::COLORSPACE_SRGB);
}
?>
It is pretty work in current stable Image Magick (6.9.0-4).

These are the basic steps to convert an image from RGB to CMYK:
$image = new Imagick();
$image->readImage(rgb.jpg);
$image->setImageColorSpace(Imagick::COLORSPACE_CMYK);
$image->profileImage('icc', file_get_contents(/path/CoatedFOGRA27.icc'));
$image->negateImage(FALSE, imagick::COLOR_CYAN);
$image->negateImage(FALSE, imagick::COLOR_MAGENTA);
$image->negateImage(FALSE, imagick::COLOR_YELLOW);
$image->negateImage(FALSE, imagick::COLOR_BLACK);
$image->writeImage(cmyk.rgb);

I have a better solution for solving inverted colors on php 5.3.x than posted. All the other solutions I found darkens the image or messes with the colors.
See below (note: my imagick object is $jpeg)
$range = $jpeg->getQuantumRange();
      $php_vs_arr = preg_split("/\./", phpversion());
      $php_vs = $php_vs_arr[0] . '.' . $php_vs_arr[1];
      if ($jpeg->getImageColorspace() == Imagick::COLORSPACE_CMYK) {
          
        //make sure cmyk color-space is set correctly
        $jpeg->setImageColorspace(12);
          
        // then we add an RGB profile
        $icc_rgb = file_get_contents(FRAMEWORK_PATH . DS . 'color' . DS . 'AdobeRGB1998.icc');
        $jpeg->profileImage('icc', $icc_rgb);
        unset($icc_rgb);
          
        //set color space to rgb
        $jpeg->setImageColorspace(13);
      
        //fix gamma, hue, saturation, brightness
        if($php_vs < 5.3) {
          //ADJUST GAMMA BY 20% for 5.2.x
          $jpeg->levelImage(0, 2.0, $range['quantumRangeString']);
        } else {
          //php 5.3 hack FOR INVERTED COLORS
          $jpeg->negateImage(false, Imagick::CHANNEL_ALL);
        }
          
      }
      $jpeg->stripImage();
      //end convert to RGB=========================|

This is how to Monochrome a jpg [on Windows].. since I couldn't find it anywhere else.
<?php
header("Content-type: image/jpeg");
$IMagick = new IMagick('c:\\testing\\fruit.jpg');
$IMagick->setImageColorSpace(Imagick::COLORSPACE_GRAY);
echo $IMagick;
?>

If your getting strange/bad color rendering from a PDF, after trying the colorspace constants noted by jdstraughan, try other values outside that range.
In one case for me only $image->setImageColorSpace(22) provided useful color. I have found posts elsewhere using values up to 255.

These are the basic steps to convert an image from RGB to CMYK:
$image = new Imagick();
$image->readImage(rgb.jpg);
$image->setImageColorSpace(Imagick::COLORSPACE_CMYK);
$image->profileImage('icc', file_get_contents(/path/CoatedFOGRA27.icc'));
$image->negateImage(FALSE, imagick::COLOR_CYAN);
$image->negateImage(FALSE, imagick::COLOR_MAGENTA);
$image->negateImage(FALSE, imagick::COLOR_YELLOW);
$image->negateImage(FALSE, imagick::COLOR_BLACK);
$image->writeImage(cmyk.rgb);
For more information: 
http://www.cesarebordi.it/imagemagick-php-convertire-rgb-to-cmyk-web-developer/