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Imagick::filter — Description
$ImagickKernel
   [, int $CHANNEL = Imagick::CHANNEL_DEFAULT
  ] )Applies a custom convolution kernel to the image.
ImagickKernelAn instance of ImagickKernel that represents either a single kernel or a linked series of kernels.
CHANNEL
      Provide any channel constant that is valid for your channel mode. To apply to more than one channel, combine channel constants using bitwise operators. 缺省为Imagick::CHANNEL_DEFAULT. 
参考此 通道常数列表
     
Example #1 Imagick::filter()
<?php
function filter($imagePath) {
    $imagick = new \Imagick(realpath($imagePath));
    $matrix = [
        [-1, 0, -1],
        [0,  5,  0],
        [-1, 0, -1],
    ];
    
    $kernel = \ImagickKernel::fromMatrix($matrix);
    $strength = 0.5;    
    $kernel->scale($strength, \Imagick::NORMALIZE_KERNEL_VALUE);    
    $kernel->addUnityKernel(1 - $strength);
    $imagick->filter($kernel);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>