educational

Image Manipulation Using PHP

Valentin Ciocea

I bet that many of you who develop websites have had this problem at least one time: how to resize, rotate and manipulate pics using PHP. I myself had this problem some time ago, and so I searched for the best solution. Among the options I found was a tool called ImageMagick.

ImageMagick is a standalone, command-line program that can be called with parameters to perform a requested change to either a single image, or to a set of images. ImageMagick is by far more complex than any other image processing tool I found, and although there may be other tools, I can recommend this one.

Since all of your image processing can be easily done by this tool, all you have to do is to install it on your Web server and then call it with the proper parameters. If you are using a Linux Web server, there are some configuration issues that you have to take care of, such as specifying full paths (paths from the root folder, not relative paths), and setting ‘umask’ to "0" in order to prevent changing file permissions in a way that will cause you problems in the future.

Here are some examples of how you can use ImageMagick:

• To Make Thumbnails:

<?
// Set the path to where the ImageMagick program is on your server
$path_imagemagick="/usr/X11R6/bin/";

// Set the path and filename to the picture
$path_picture="/www/sitename/pictures/picture1.jpg";

// Set the path and filename to where the thumb will be created
$path_thumb="/www/sitename/thumbs/thumb1.jpg";

// Set the largest dimension of the thumbnail (width for landscape and height for portraits)
$thumbnail_size=120;

// Set umask to 0 in order not to affect the file permissions during the next operation
umask(000);

// Execute the shell command that calls Image Magick with the proper parameters (as set above)
$ok=shell_exec($path_imagemagick."convert -size $thumbnail_size $path_picture -geometry $thumbnail_size $path_thumb");

// If shell_exec above returns 1 this mean that the operation was sucessful.
if ($ok)
{
echo "Thumbnail Created OK";
}

?>

• To Resize Images:
This is done the same way as above, except that the $path_thumb (which is the destination file) will have the same value as $path_picture – and this way the script will resize the original image, rather than create a new image.

• To Rotate Images:
To rotate an image, you must decide how much to rotate it (the number of degrees), and in which direction. Actually, all you have to know is the number of degrees you wish to rotate, since the direction is indicated by the plus and minus sign. So, +90 degrees means to rotate the pic counter clockwise for a quarter of circle (full circle is 360 degrees); -90 meens to rotate it clockwise for a quarter of circle:

<?
// Set the path to where the ImageMagick program is on your server
$path_imagemagick="/usr/X11R6/bin/";

// Set the path and filename to the picture
$path_picture="/www/sitename/pictures/picture1.jpg";

// Set the degrees with whom the picture will be rotated. Positive means counter clockwise and negative clockwise.
$degrees=-90;

// Set umask to 0 in order not to affect the file permissions with the next operation
umask(000);
$ok=shell_exec ($path_imagemagick."convert -rotate $degrees $path_picture $path_picture");

// If shell_exec above returns 1 this mean that the operation was sucessful.
if ($ok)
{
echo "Picture Rotated OK";
}

?>

• Apply A Watermark:

To do this, you will need to have an aditional image that will be used for the watermark.

<?
// Set the path to where the ImageMagick program is on your server
$path_imagemagick="/usr/X11R6/bin/";

// Set the path and filename to the picture
$path_picture="/www/sitename/pictures/picture1.jpg";

// Set the path and filename to the watermark picture
$path_watermark="/www/sitename/images/watermark.jpg";

// Set umask to 0 in order to not affect the file permissions during the next operation
umask(000);
$ok=shell_exec ($path_imagemagick."composite -watermark 15x70 -gravity SouthEast $path_watermark $path_picture
$path_picture");

// If shell_exec above returns 1 this mean that the operation was sucessful.
if ($ok)
{
echo "Picture Watermarked OK";
}

?>

As you can see, ImageMagick is a great tool for dynamically processing images using a PHP-enabled Web server. Try it for yourself, and see how easy automating your image manipulation tasks can be!

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