{ "content": [ { "type": "text", "text": "# pnmcolormap (info)\n\n## NAME\n\npnmcolormap - create quantization color map for a portable anymap\n\n## SYNOPSIS\n\npnmcolormap [-center|-meancolor|-meanpixel] [-spreadbrightness|-spread-\nluminosity] [-sort] [-square] ncolors|all [pnmfile]\nAll options can be abbreviated to their shortest unique prefix. You\nmay use two hyphens instead of one to designate an option. You may use\neither white space or an equals sign between an option name and its\nvalue.\n\n## DESCRIPTION\n\nReads a PNM image as input. Chooses ncolors colors to best represent\nthe image, maps the existing colors to the new ones, and writes a PNM\ncolor map defining them as output.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **PARAMETERS** (7 subsections)\n- **QUANTIZATION METHOD**\n- **REFERENCES**\n- **SEE ALSO**\n- **AUTHOR**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n" } ], "structuredContent": { "command": "pnmcolormap", "section": "", "mode": "info", "summary": "pnmcolormap - create quantization color map for a portable anymap", "synopsis": "pnmcolormap [-center|-meancolor|-meanpixel] [-spreadbrightness|-spread-\nluminosity] [-sort] [-square] ncolors|all [pnmfile]\nAll options can be abbreviated to their shortest unique prefix. You\nmay use two hyphens instead of one to designate an option. You may use\neither white space or an equals sign between an option name and its\nvalue.", "tldr_summary": null, "tldr_examples": [], "tldr_source": null, "flags": [], "examples": [], "see_also": [ { "name": "pnmremap", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/pnmremap/1/json" }, { "name": "pnmquant", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/pnmquant/1/json" }, { "name": "ppmquantall", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ppmquantall/1/json" }, { "name": "pnmdepth", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/pnmdepth/1/json" }, { "name": "ppmdither", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ppmdither/1/json" }, { "name": "ppmquant", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ppmquant/1/json" }, { "name": "ppm", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/ppm/5/json" } ], "section_outline": [ { "name": "NAME", "lines": 2, "subsections": [] }, { "name": "SYNOPSIS", "lines": 8, "subsections": [] }, { "name": "DESCRIPTION", "lines": 26, "subsections": [] }, { "name": "PARAMETERS", "lines": 13, "subsections": [ { "name": "-square", "lines": 7 }, { "name": "-verbose", "lines": 3 }, { "name": "-center", "lines": 1 }, { "name": "-meancolor", "lines": 1 }, { "name": "-meanpixel", "lines": 1 }, { "name": "-spreadbrightness", "lines": 1 }, { "name": "-spreadluminosity", "lines": 3 } ] }, { "name": "QUANTIZATION METHOD", "lines": 33, "subsections": [] }, { "name": "REFERENCES", "lines": 3, "subsections": [] }, { "name": "SEE ALSO", "lines": 3, "subsections": [] }, { "name": "AUTHOR", "lines": 4, "subsections": [] } ], "sections": { "NAME": { "content": "pnmcolormap - create quantization color map for a portable anymap\n", "subsections": [] }, "SYNOPSIS": { "content": "pnmcolormap [-center|-meancolor|-meanpixel] [-spreadbrightness|-spread-\nluminosity] [-sort] [-square] ncolors|all [pnmfile]\n\nAll options can be abbreviated to their shortest unique prefix. You\nmay use two hyphens instead of one to designate an option. You may use\neither white space or an equals sign between an option name and its\nvalue.\n", "subsections": [] }, "DESCRIPTION": { "content": "Reads a PNM image as input. Chooses ncolors colors to best represent\nthe image, maps the existing colors to the new ones, and writes a PNM\ncolor map defining them as output.\n\nYou can use this map as input to pnmremap on the same input image to\nquantize the colors in that image, I.e. produce a similar image with\nfewer colors. pnmquant does both the pnmcolormap and pnmremap steps\nfor you.\n\nA PNM colormap is a PNM image of any dimensions that contains at least\none pixel of each color in the set of colors it represents.\n\nThe quantization method is Heckbert's \"median cut\". See the section\nQUANTIZATION METHOD.\n\nIf the input image is a PPM, the output image is a PPM. If the input\nimage is a PBM or PGM, the output colormap is a PGM. Note that a col-\normap of a PBM image is not very interesting.\n\nThe colormap generally has the same maxval as the input image, but pnm-\ncolormap may reduce it if there are too many colors in the input, as\npart of its quantization algorithm.\n\nIf you want to create a colormap without basing it on the colors in an\ninput image, see ppmcolors.\n", "subsections": [] }, "PARAMETERS": { "content": "The single parameter, which is required, is the number of colors you\nwant in the output colormap. pnmcolormap may produce a color map with\nslightly fewer colors than that. You may specify all to get a colormap\nof every color in the input image (no quantization).\n\nOPTIONS\n\n-sort This option causes the output colormap to be sorted by the red\ncomponent intensity, then the green, then the blue in ascending\norder. This is an insertion sort, so it is not very fast on\nlarge colormaps. Sorting is useful because it allows you to\ncompare two sets of colors.\n", "subsections": [ { "name": "-square", "content": "By default, pnmcolormap produces as the color map a PPM image\nwith one row and one column for each color in the colormap.\nThis option causes pnmcolormap instead to produce a PPM image\nthat is within one row or column of being square, with multiple\npixels of the same color as necessary to create a number of pix-\nels which is a perfect square.\n" }, { "name": "-verbose", "content": "This option causes pnmcolormap to display messages to Standard\nError about the quantization.\n" }, { "name": "-center", "content": "" }, { "name": "-meancolor", "content": "" }, { "name": "-meanpixel", "content": "" }, { "name": "-spreadbrightness", "content": "" }, { "name": "-spreadluminosity", "content": "These options control the quantization algorithm. See QUANTIZA-\nTION METHOD below.\n" } ] }, "QUANTIZATION METHOD": { "content": "A quantization method is a way to choose which colors, being fewer in\nnumber than in the input, you want in the output. pnmcolormap uses\nHeckbert's \"median cut\" quantization method.\n\nThis method involves separating all the colors into \"boxes,\" each hold-\ning colors that represent about the same number of pixels. You start\nwith one box and split boxes in two until the number of boxes is the\nsame as the number of colors you want in the output, and choose one\ncolor to represent each box.\n\nWhen you split a box, you do it so that all the colors in one sub-box\nare \"greater\" than all the colors in the other. \"Greater,\" for a par-\nticular box, means it is brighter in the color component (red, green,\nblue) which has the largest spread in that box. pnmcolormap gives you\ntwo ways to define \"largest spread.\": 1) largest spread of brightness;\n2) largest spread of contribution to the luminosity of the color. E.g.\nred is weighted much more than blue. Select among these with the\n-spreadbrightness and -spreadluminosity options. The default is\n-spreadbrightness.\n\npnmcut provides three ways of choosing a color to represent a box: 1)\nthe center color - the color halfway between the greatest and least\ncolors in the box, using the above definition of \"greater\"; 2) the mean\nof the colors (each component averaged separately by brightness) in the\nbox; 3) the mean weighted by the number of pixels of a color in the im-\nage.\n\nNote that in all three methods, there may be colors in the output which\ndo not appear in the input at all.\n\nSelect among these with the -center, -meancolor, and -meanpixel op-\ntions. The default is -center.\n", "subsections": [] }, "REFERENCES": { "content": "\"Color Image Quantization for Frame Buffer Display\" by Paul Heckbert,\nSIGGRAPH '82 Proceedings, page 297.\n", "subsections": [] }, "SEE ALSO": { "content": "pnmremap(1), pnmquant(1), ppmquantall(1), pnmdepth(1), ppmdither(1),\nppmquant(1), ppm(5)\n", "subsections": [] }, "AUTHOR": { "content": "Copyright (C) 1989, 1991 by Jef Poskanzer. Copyright (C) 2001 by Bryan\nHenderson.\n\n12 December 2001 pnmcolormap(1)", "subsections": [] } } } }