(PECL imagick 2.0.0)
Imagick::sepiaToneImage — Sepia tones an image
$threshold
   )Applies a special effect to the image, similar to the effect achieved in a photo darkroom by sepia toning. Threshold ranges from 0 to QuantumRange and is a measure of the extent of the sepia toning. A threshold of 80 is a good starting point for a reasonable tone.
threshold
   Returns TRUE on success.
  
Throws ImagickException on error.
Example #1 Imagick::sepiaToneImage()
<?php
function sepiaToneImage($imagePath, $sepia) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->sepiaToneImage($sepia);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>