(PHP 4 >= 4.0.7, PHP 5)
imagegd — Output GD image to browser or file
Outputs a GD image to the given filename .
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
The path to save the file to. If not set or NULL, the raw image stream will be outputted directly.
如果成功則回傳 TRUE,失敗則回傳 FALSE。
Note: The GD format is commonly used to allow fast loading of parts of images. Note that the GD format is only usable in GD-compatible applications.