By default, chrominance samples are created by sampling 2 by 2 blocks of luminance values; this can be changed with the -h and -v options. Output data are compressed with the PackBits compression scheme, by default; an alternate scheme can be selected with the -c option. By default, output data are compressed in strips with the number of rows in each strip selected so that the size of a strip is never more than 8 kilobytes; the -r option can be used to explicitly set the number of rows per strip.
|-c||Specify a compression scheme to use when writing image data: -c none for no compression, -c packbits for the PackBits compression algorithm (the default), -c jpeg for the JPEG compression algorithm, -c zip for the deflate compression algorithm, and -c lzw for Lempel-Ziv & Welch.|
|-h||Set the horizontal sampling dimension to one of: 1, 2 (default), or 4.|
|-r||Write data with a specified number of rows per strip; by default the number of rows/strip is selected so that each strip is approximately 8 kilobytes.|
|-v||Set the vertical sampling dimension to one of: 1, 2 (default), or 4.|