usage: cjpeg [switches] [inputfile]
Switches (names may be abbreviated):
  -quality N[,...]   Compression quality (0..100; 5-95 is useful range)
  -grayscale     Create monochrome JPEG file
  -rgb           Create RGB JPEG file
  -optimize      Optimize Huffman table (smaller file, but slow compression)
  -progressive   Create progressive JPEG file
  -scale M/N     Scale image by fraction M/N, eg, 1/2
  -targa         Input file is Targa format (usually not needed)
Switches for advanced users:
  -arithmetic    Use arithmetic coding
  -block N       DCT block size (1..16; default is 8)
  -rgb1          Create RGB JPEG file with reversible color transform
  -bgycc         Create big gamut YCC JPEG file
  -dct int       Use integer DCT method (default)
  -dct fast      Use fast integer DCT (less accurate)
  -dct float     Use floating-point DCT method
  -nosmooth      Don't use high-quality downsampling
  -restart N     Set restart interval in rows, or in blocks with B
  -smooth N      Smooth dithered input (N=1..100 is strength)
  -maxmemory N   Maximum memory to use (in kbytes)
  -outfile name  Specify name for output file
  -verbose  or  -debug   Emit debug output
Switches for wizards:
  -baseline      Force baseline quantization tables
  -qtables file  Use quantization tables given in file
  -qslots N[,...]    Set component quantization tables
  -sample HxV[,...]  Set component sampling factors