Custom Image Formats

If you want to support a custom image format, you have to declare a "file mapper" class for each format. It's role is to map images to files and vice versa. The class has to conform to a few simple rules.

Naming the class

You have to name the class properly: wiImageFileMapper_FORMAT. So, if you want to support tga files, you have to name the class wiImageFileMapper_TGA. WideImage will automatically create and use the mapper.

Methods

In order for the mapper to work, a few methods must be defined properly; a parameterless constructor, load method and save method.

load()

Signature: load($uri)
Parameters:
- $uri string - URI (file or URL) of an image
Return value: null or a valid GD image resource, like one created with imagecreate()∞ or imagecreatetruecolor()∞.

save()

Signature: save($handle, $uri = null [, custom parameters])
Parameters:
- $handle resource - a GD image resource
- $uri string/null - target file. Null for no file (mapper must output image directly).
- custom parameters - whatever you define
Return value: none.

Example of a File Mapper

class wiImageFileMapper_PCX

{

  function load($uri)

  {

  $data = file_get_contents($uri);

  // determine width & height from the file header

  $handle = imagecreatetruecolor($width, $height);

  // read pixels from the file data and write them to $handle

  return $handle;

  }

  // define some custom parameters with default values

  function save($handle, $uri = null, $quality = 100, $interlaced = false)

  {

  if ($uri == null)

  {

    // output image

  }

  else

  {

    // write to file

    $fp = fopen($uri, 'w');

    // write to file

    fclose($fp);

  }

  }

}

And now let's use it: