image2wbmp() outputs or save a WBMP
version of the given image.
Parameters
image
An image resource, returned by one of the image creation functions,
such as imagecreatetruecolor().
filename
Path to the saved file. If not given, the raw image stream will be
output directly.
foreground
You can set the foreground color with this parameter by setting an
identifier obtained from imagecolorallocate().
The default foreground color is black.