Use this option to specify the width and height of raw images whose dimensions are unknown such as GRAY, RGB, or CMYK. In addition to width and height, use this option to skip any header information in the image (e.g. `640x512+256`).

The format of the size option:

        <width>{%}x<height>{%}{+offset}{!}

For Photo CD images, choose from these sizes:

       192x128
       384x256
       768x512
       1536x1024
       3072x2048

Finally, use this option to choose a particular resolution layer of a JBIG or JPEG image (e.g `768x512`).