Grayscale image

<?php  
  $image = imagecreatefromjpeg( "input.jpg" );
  imagefilter( $image, IMG_FILTER_GRAYSCALE, $args );
  imagejpeg( $image, 'output.jpg' );
  imagedestroy( $image );
?>

Use a filter to change an image to grayscale. There are other filters check the link below. Note: needs php 5.

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