Understanding Image Compression Type in PHP with the ImageMagick Package

The ImageMagick PHP function for getCompression returns an integer representing the value associated with the ImageMagick Compression constant.  You'll get numbers from 0 to 13, each representing a different particular type of compression.  If printed out, the ImageMagick constants for compression come out as...

imagick::COMPRESSION_UNDEFINED    0
imagick::COMPRESSION_NO    1
imagick::COMPRESSION_BZIP    2
imagick::COMPRESSION_DXT1    3
imagick::COMPRESSION_DXT3    4
imagick::COMPRESSION_DXT5    5
imagick::COMPRESSION_FAX    6
imagick::COMPRESSION_GROUP4    7
imagick::COMPRESSION_JPEG    8
imagick::COMPRESSION_JPEG2000    9
imagick::COMPRESSION_LOSSLESSJPEG    10
imagick::COMPRESSION_LZW    11
imagick::COMPRESSION_RLE    12
imagick::COMPRESSION_ZIP    13

Every time I have used this, whether on a jpeg image, a png image, a gif image, or a bmp image, it has always returned '0' as a value.  There's a good chance that this is simply a value that is set by means of get/set, as opposed to actually producing values for a given image.

Some sample code :

<?php

            // Author: holdoffhunger@gmail.com
   
        // Imagick Type
        // ---------------------------------------------

    $imagick_type = new Imagick();
   
        // Open File
        // ---------------------------------------------
       
    $file_to_grab = "image_workshop_directory/test.bmp";
   
    $file_handle_for_viewing_image_file = fopen($file_to_grab, 'a+');
   
        // Grab File
        // ---------------------------------------------

    $imagick_type->readImageFile($file_handle_for_viewing_image_file);
   
        // Get Quantum Range
        // ---------------------------------------------
       
    $imagick_type_compression = $imagick_type->getCompression();
   
        // Print Results
        // ---------------------------------------------

    print("<pre>");
    print($imagick_type_compression);
    print("</pre>");

?>

Official Function Page: http://www.php.net/manual/en/imagick.getcompression.php

// Note: All code appearing on the PHP Revolution blog by the blog owner is released under the Hacktivismo Enhanced-Source Software License Agreement (HESSLA), unless otherwise noted.  http://www.hacktivismo.com/about/hessla.php