package draw9 import "image" // Compressed image file parameters.const (	NMATCH  = 3             /* shortest match possible */	NRUN    = (NMATCH + 31) /* longest match possible */	NMEM    = 1024          /* window size */	NDUMP   = 128           /* maximum length of dump */	NCBLOCK = 6000          /* size of compressed blocks */) /* * compressed data are sequences of byte codes. * if the first byte b has the 0x80 bit set, the next (b^0x80)+1 bytes * are data.  otherwise, it's two bytes specifying a previous string to repeat. */ func twiddlecompressed(buf []byte) {	i := 0	for i < len(buf) {		c := buf[i]		i++		if c >= 0x80 {			k := int(c) - 0x80 + 1			for j := 0; j < k && i < len(buf); j++ {				buf[i] ^= 0xFF				i++			}		} else {			i++		}	}} func compblocksize(r image.Rectangle, depth int) int {	bpl := BytesPerLine(r, depth)	bpl = 2 * bpl /* add plenty extra for blocking, etc. */	if bpl < NCBLOCK {		return NCBLOCK	}	return bpl}