SGI Freeware 1999 August

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Text File | 1999-01-26 | 13.2 KB | 265 lines

DDDDJJJJPPPPEEEEGGGG((((1111)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22222222 AAAAuuuugggguuuusssstttt 1111999999997777)))) DDDDJJJJPPPPEEEEGGGG((((1111)))) NNNNAAAAMMMMEEEE djpeg - decompress a JPEG file to an image file SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS ddddjjjjppppeeeegggg [ _o_p_t_i_o_n_s ] [ _f_i_l_e_n_a_m_e ] DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN ddddjjjjppppeeeegggg decompresses the named JPEG file, or the standard input if no file is named, and produces an image file on the standard output. PBMPLUS (PPM/PGM), BMP, GIF, Targa, or RLE (Utah Raster Toolkit) output format can be selected. (RLE is supported only if the URT library is available.) OOOOPPPPTTTTIIIIOOOONNNNSSSS All switch names may be abbreviated; for example, ----ggggrrrraaaayyyyssssccccaaaalllleeee may be written ----ggggrrrraaaayyyy or ----ggggrrrr. Most of the "basic" switches can be abbreviated to as little as one letter. Upper and lower case are equivalent (thus ----BBBBMMMMPPPP is the same as ----bbbbmmmmpppp). British spellings are also accepted (e.g., ----ggggrrrreeeeyyyyssssccccaaaalllleeee), though for brevity these are not mentioned below. The basic switches are: ----ccccoooolllloooorrrrssss _N Reduce image to at most N colors. This reduces the number of colors used in the output image, so that it can be displayed on a colormapped display or stored in a colormapped file format. For example, if you have an 8-bit display, you'd need to reduce to 256 or fewer colors. ----qqqquuuuaaaannnnttttiiiizzzzeeee _N Same as ----ccccoooolllloooorrrrssss. ----ccccoooolllloooorrrrssss is the recommended name, ----qqqquuuuaaaannnnttttiiiizzzzeeee is provided only for backwards compatibility. ----ffffaaaasssstttt Select recommended processing options for fast, low quality output. (The default options are chosen for highest quality output.) Currently, this is equivalent to ----ddddcccctttt ffffaaaasssstttt ----nnnnoooossssmmmmooooooootttthhhh ----oooonnnneeeeppppaaaassssssss ----ddddiiiitttthhhheeeerrrr oooorrrrddddeeeerrrreeeedddd. ----ggggrrrraaaayyyyssssccccaaaalllleeee Force gray-scale output even if JPEG file is color. Useful for viewing on monochrome displays; also, ddddjjjjppppeeeegggg runs noticeably faster in this mode. ----ssssccccaaaalllleeee _M/_N Scale the output image by a factor M/N. Currently the scale factor must be 1/1, 1/2, 1/4, or 1/8. Scaling is handy if the image is larger than your screen; also, ddddjjjjppppeeeegggg runs much faster when scaling down the output. Page 1 (printed 12/16/98) DDDDJJJJPPPPEEEEGGGG((((1111)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22222222 AAAAuuuugggguuuusssstttt 1111999999997777)))) DDDDJJJJPPPPEEEEGGGG((((1111)))) ----bbbbmmmmpppp Select BMP output format (Windows flavor). 8-bit colormapped format is emitted if ----ccccoooolllloooorrrrssss or ----ggggrrrraaaayyyyssssccccaaaalllleeee is specified, or if the JPEG file is gray-scale; otherwise, 24-bit full-color format is emitted. ----ggggiiiiffff Select GIF output format. Since GIF does not support more than 256 colors, ----ccccoooolllloooorrrrssss 222255556666 is assumed (unless you specify a smaller number of colors). ----oooossss2222 Select BMP output format (OS/2 1.x flavor). 8-bit colormapped format is emitted if ----ccccoooolllloooorrrrssss or ----ggggrrrraaaayyyyssssccccaaaalllleeee is specified, or if the JPEG file is gray-scale; otherwise, 24-bit full-color format is emitted. ----ppppnnnnmmmm Select PBMPLUS (PPM/PGM) output format (this is the default format). PGM is emitted if the JPEG file is gray-scale or if ----ggggrrrraaaayyyyssssccccaaaalllleeee is specified; otherwise PPM is emitted. ----rrrrlllleeee Select RLE output format. (Requires URT library.) ----ttttaaaarrrrggggaaaa Select Targa output format. Gray-scale format is emitted if the JPEG file is gray-scale or if ----ggggrrrraaaayyyyssssccccaaaalllleeee is specified; otherwise, colormapped format is emitted if ----ccccoooolllloooorrrrssss is specified; otherwise, 24-bit full-color format is emitted. Switches for advanced users: ----ddddcccctttt iiiinnnntttt Use integer DCT method (default). ----ddddcccctttt ffffaaaasssstttt Use fast integer DCT (less accurate). ----ddddcccctttt ffffllllooooaaaatttt Use floating-point DCT method. The float method is very slightly more accurate than the int method, but is much slower unless your machine has very fast floating-point hardware. Also note that results of the floating-point method may vary slightly across machines, while the integer methods should give the same results everywhere. The fast integer method is much less accurate than the other two. ----ddddiiiitttthhhheeeerrrr ffffssss Use Floyd-Steinberg dithering in color quantization. ----ddddiiiitttthhhheeeerrrr oooorrrrddddeeeerrrreeeedddd Use ordered dithering in color quantization. Page 2 (printed 12/16/98) DDDDJJJJPPPPEEEEGGGG((((1111)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22222222 AAAAuuuugggguuuusssstttt 1111999999997777)))) DDDDJJJJPPPPEEEEGGGG((((1111)))) ----ddddiiiitttthhhheeeerrrr nnnnoooonnnneeee Do not use dithering in color quantization. By default, Floyd-Steinberg dithering is applied when quantizing colors; this is slow but usually produces the best results. Ordered dither is a compromise between speed and quality; no dithering is fast but usually looks awful. Note that these switches have no effect unless color quantization is being done. Ordered dither is only available in ----oooonnnneeeeppppaaaassssssss mode. ----mmmmaaaapppp _f_i_l_e Quantize to the colors used in the specified image file. This is useful for producing multiple files with identical color maps, or for forcing a predefined set of colors to be used. The _f_i_l_e must be a GIF or PPM file. This option overrides ----ccccoooolllloooorrrrssss and ----oooonnnneeeeppppaaaassssssss. ----nnnnoooossssmmmmooooooootttthhhh Use a faster, lower-quality upsampling routine. ----oooonnnneeeeppppaaaassssssss Use one-pass instead of two-pass color quantization. The one-pass method is faster and needs less memory, but it produces a lower-quality image. ----oooonnnneeeeppppaaaassssssss is ignored unless you also say ----ccccoooolllloooorrrrssss _N. Also, the one- pass method is always used for gray-scale output (the two-pass method is no improvement then). ----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy _N Set limit for amount of memory to use in processing large images. Value is in thousands of bytes, or millions of bytes if "M" is attached to the number. For example, ----mmmmaaaaxxxx 4444mmmm selects 4000000 bytes. If more space is needed, temporary files will be used. ----oooouuuuttttffffiiiilllleeee _n_a_m_e Send output image to the named file, not to standard output. ----vvvveeeerrrrbbbboooosssseeee Enable debug printout. More ----vvvv's give more output. Also, version information is printed at startup. ----ddddeeeebbbbuuuugggg Same as ----vvvveeeerrrrbbbboooosssseeee. EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS This example decompresses the JPEG file foo.jpg, quantizes it to 256 colors, and saves the output in 8-bit BMP format in foo.bmp: ddddjjjjppppeeeegggg ----ccccoooolllloooorrrrssss 222255556666 ----bbbbmmmmpppp _f_o_o._j_p_g >>>> _f_o_o._b_m_p Page 3 (printed 12/16/98) DDDDJJJJPPPPEEEEGGGG((((1111)))) UUUUNNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((22222222 AAAAuuuugggguuuusssstttt 1111999999997777)))) DDDDJJJJPPPPEEEEGGGG((((1111)))) HHHHIIIINNNNTTTTSSSS To get a quick preview of an image, use the ----ggggrrrraaaayyyyssssccccaaaalllleeee and/or ----ssssccccaaaalllleeee switches. ----ggggrrrraaaayyyyssssccccaaaalllleeee ----ssssccccaaaalllleeee 1111////8888 is the fastest case. Several options are available that trade off image quality to gain speed. ----ffffaaaasssstttt turns on the recommended settings. ----ddddcccctttt ffffaaaasssstttt and/or ----nnnnoooossssmmmmooooooootttthhhh gain speed at a small sacrifice in quality. When producing a color-quantized image, ----oooonnnneeeeppppaaaassssssss ----ddddiiiitttthhhheeeerrrr oooorrrrddddeeeerrrreeeedddd is fast but much lower quality than the default behavior. ----ddddiiiitttthhhheeeerrrr nnnnoooonnnneeee may give acceptable results in two-pass mode, but is seldom tolerable in one- pass mode. If you are fortunate enough to have very fast floating point hardware, ----ddddcccctttt ffffllllooooaaaatttt may be even faster than ----ddddcccctttt ffffaaaasssstttt. But on most machines ----ddddcccctttt ffffllllooooaaaatttt is slower than ----ddddcccctttt iiiinnnntttt; in this case it is not worth using, because its theoretical accuracy advantage is too small to be significant in practice. EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT JJJJPPPPEEEEGGGGMMMMEEEEMMMM If this environment variable is set, its value is the default memory limit. The value is specified as described for the ----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy switch. JJJJPPPPEEEEGGGGMMMMEEEEMMMM overrides the default value specified when the program was compiled, and itself is overridden by an explicit ----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy. SSSSEEEEEEEE AAAALLLLSSSSOOOO ccccjjjjppppeeeegggg(1), jjjjppppeeeeggggttttrrrraaaannnn(1), rrrrddddjjjjppppggggccccoooommmm(1), wwwwrrrrjjjjppppggggccccoooommmm(1) ppppppppmmmm(5), ppppggggmmmm(5) Wallace, Gregory K. "The JPEG Still Picture Compression Standard", Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44. AAAAUUUUTTTTHHHHOOOORRRR Independent JPEG Group BBBBUUUUGGGGSSSS Arithmetic coding is not supported for legal reasons. To avoid the Unisys LZW patent, ddddjjjjppppeeeegggg produces uncompressed GIF files. These are larger than they should be, but are readable by standard GIF decoders. Still not as fast as we'd like. Page 4 (printed 12/16/98)