Drupal 7 Module Development

Working with Files and Images
The scale case uses image_scale(), which takes four arguments. The first two are
the target height and width of the new image. Since image_scale() preserves an
image's aspect ratio, you actually only need to provide one of these, and you can
leave the other one NULL, as we've done in the example. If you provide both values,
one of them may end up smaller than specified because of the calculations needed
to preserve the image's aspect ratio. The last argument specifies whether or not
image_scale() should upscale an image when you provide a height and/or width
that is larger than the original. This typically results in a lower quality pixilated
image, so we have specified FALSE.
Finally, the rotate case uses image_rotate(), which takes two arguments. The first
is the number of degrees the image should be rotated to, and the second specifies an
optional background color that should be used to fill in any space left behind by the
rotation. This color should be specified using the color's hex value. In this example,
we rotate 45 degrees and fill the background with purple.
Finally we need to save and display the resulting image:
$local_uri =drupal_tempnam('public://');
image_save($local_image, $local_uri);
}
return theme('image', array('path' => $local_uri));
We create a local filename using drupal_tempnam(), which just generates a random
filename we can use when given a path. It may seem tempting to use information like
the file's Twitpic ID or the operation to be performed in the file's name. However, in
this example, these items are passed in through the URL, and this cannot be trusted. It
is possible to create a security problem if you are not very careful using user-submitted
data in filenames, and thus it is best to avoid that, if at all possible.
We can now pass this path, along with our modified image object, to image_save(),
to save our image to the public filesystem. Once saved, it is a simple matter to call
the theme function for images, to generate the necessary HTML for our image to
be displayed. The following is an example of what you would see when requesting
twitpic/munge/7nyr2/rotate:
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