An image or imagelist to be used as the watermark. The watermark must be grayscale and should be substantially smaller than the receiver. The recovery time is proportional to the size of the watermark.
The starting position within the receiver at which the watermark will be hidden. When you retrieve the watermark from the file, you must supply this value, along with the width and height of the watermark, in the size optional parameter to the read method.
Hides a digital watermark in the receiver. You can retrieve the watermark by reading the file with the stegano: prefix, thereby proving the authenticity of the file.
The watermarked image must be saved in a lossless RGB format such as MIFF, or PNG. You cannot save a watermarked image in a lossy format such as JPEG or a pseudocolor format such as GIF. Once written, the file must not be modified or processed in any way.