get the paintCompression of image
set the paintCompression to {png | jpeg | gif | rle}
set the paintCompression to "PNG"
if the paintCompression of image "Photo" is "pict" then warnUser
Use the paintCompression property to obtain the format of images, or to change the format used for new images.
Value:
The paintCompression is one of the following: "png", "jpeg", "gif", or "rle". By default, the global paintCompression property is set to "rle" in standalones and "png" in the development environment.
The paintCompression of an image is one of the following: "png", "jpeg", "gif", "rle", or "pict". By default, the paintCompression property of a newly created image is set to "rle" if it was created with the create command or by using a paint tool. If the image was created with the import command, its paintCompression is set to the format of the imported picture file.
For images, this property is read-only and cannot be set; you can set only the global paintCompression.
Comments:
When an image is changed with a paint tool, it is recompressed the next time you leave the card it's on. The format in which it is compressed is set by the global paintCompression property.
To change an image's compression format, first set the paintCompression to the desired value, then paint in the image. Then either go to another card and return, or close and re-open the stack.
Cross-platform note: On Mac OS and OS X systems, PICTfiles can be imported, and the paintCompression of the resulting image is set to pict. However, PICT images cannot be displayed on Unix or Windows systems unless they are converted to another format.
If an image's alphaData property contains any value other than 255 (opaque), it is automatically recompressed in PNG format to preserve the alpha channel data.
