{
    "mode": "man",
    "parameter": "ppmchange",
    "section": "1",
    "url": "https://www.chedong.com/phpMan.php/man/ppmchange/1/json",
    "generated": "2026-06-03T00:29:57Z",
    "synopsis": "ppmchange [ -closeness closenesspercent ] [ -remainder remaindercolor ] [ oldcolor newcolor\n] ...  [ppmfile]",
    "sections": {
        "NAME": {
            "content": "ppmchange - change all pixels of one color to another in a portable pixmap\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "ppmchange [ -closeness closenesspercent ] [ -remainder remaindercolor ] [ oldcolor newcolor\n] ...  [ppmfile]\n\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "Reads a portable pixmap as input.  Changes all pixels of oldcolor to newcolor.  You may spec‐\nify  up  to 256 oldcolor/newcolor pairs on the command line.  ppmchange leaves all colors not\nmentioned unchanged, unless you specify the -remainder option, in which  case  they  are  all\nchanged to the single specified color.\n\nYou  can specify that colors similar, but not identical, to the ones you specify get replaced\nby specifying a \"closeness\" factor.\n\n\nThe colors can be specified in five ways:\n\no      A name, assuming that a pointer to an X11-style color names file was compiled in.\n\no      An X11-style hexadecimal specifier: rgb:r/g/b, where r g and b are each 1- to  4-digit\nhexadecimal numbers.\n\no      An X11-style decimal specifier: rgbi:r/g/b, where r g and b are floating point numbers\nbetween 0 and 1.\n\no      For backwards compatibility,  an  old-X11-style  hexadecimal  number:  #rgb,  #rrggbb,\n#rrrgggbbb, or #rrrrggggbbbb.\n\no      For  backwards compatibility, a triplet of numbers separated by commas: r,g,b, where r\ng and b are floating point numbers between 0 and 1.  (This style was added before  MIT\ncame up with the similar rgbi style.)\n\nIf a pixel matches two different oldcolors, ppmchange replaces it with the newcolor of\nthe leftmost specified one.\n\n\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-closeness",
                    "content": "closeness is an integer per centage indicating how close to the color you specified  a\npixel must be to get replaced.  By default, it is 0, which means the pixel must be the\nexact color you specified.\n\nA pixel gets replaced if the distance in color between it and the color you  specified\nis less than or equal to closeness.\n\nThe  \"distance\" in color is defined as the cartesian sum of the individual differences\nin red, green, and blue intensities between the two pixels,  normalized  so  that  the\ndifference between black and white is 100%.\n\nThis is probably simpler than what you want most the time.  You probably would like to\nchange colors that have similar chrominance, regardless of  their  intensity.   So  if\nthere's  a red barn that is variously shadowed, you want the entire barn changed.  But\nbecause the shadowing significantly changes the color according  to  ppmchange's  dis‐\ntance  formula,  parts  of  the barn are probably about as distant in color from other\nparts of the barn as they are from green grass next to the barn.\n\nMaybe ppmchange will be enhanced some day to do chrominance analysis.\n\n"
                },
                {
                    "name": "-remainder",
                    "content": "ppmchange changes all pixels which are not of a color for which  you  specify  an  ex‐\nplicit replacement color on the command line to color color.\n\nAn example application of this is\n\nppmchange -remainder=black red red\n\nto lift only the red portions from an image, or\n\nppmchange -remainder=black red white | ppmtopgm\n\nto create a mask file for the red portions of the image.\n\n"
                }
            ]
        },
        "SEE ALSO": {
            "content": "pgmtoppm(1), ppmcolormask(1), ppm(5)\n\n",
            "subsections": []
        },
        "AUTHOR": {
            "content": "Wilson  H.  Bent. Jr. (whb@usc.edu) with modifications by Alberto Accomazzi (alberto@cfa.har‐\nvard.edu)\n\n\n\n07 January 2001                              ppmchange(1)",
            "subsections": []
        }
    },
    "summary": "ppmchange - change all pixels of one color to another in a portable pixmap",
    "flags": [
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "closeness is an integer per centage indicating how close to the color you specified a pixel must be to get replaced. By default, it is 0, which means the pixel must be the exact color you specified. A pixel gets replaced if the distance in color between it and the color you specified is less than or equal to closeness. The \"distance\" in color is defined as the cartesian sum of the individual differences in red, green, and blue intensities between the two pixels, normalized so that the difference between black and white is 100%. This is probably simpler than what you want most the time. You probably would like to change colors that have similar chrominance, regardless of their intensity. So if there's a red barn that is variously shadowed, you want the entire barn changed. But because the shadowing significantly changes the color according to ppmchange's dis‐ tance formula, parts of the barn are probably about as distant in color from other parts of the barn as they are from green grass next to the barn. Maybe ppmchange will be enhanced some day to do chrominance analysis."
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "ppmchange changes all pixels which are not of a color for which you specify an ex‐ plicit replacement color on the command line to color color. An example application of this is ppmchange -remainder=black red red to lift only the red portions from an image, or ppmchange -remainder=black red white | ppmtopgm to create a mask file for the red portions of the image."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "pgmtoppm",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/pgmtoppm/1/json"
        },
        {
            "name": "ppmcolormask",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/ppmcolormask/1/json"
        },
        {
            "name": "ppm",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/ppm/5/json"
        }
    ],
    "tldr": {
        "source": "official",
        "description": "Change all pixels of one color in a PPM image to another color.",
        "examples": [
            {
                "description": "Exchange the first color in each `oldcolor` - `newcolor` pair with the second color",
                "command": "ppmchange {{oldcolor1 newcolor1 oldcolor2 newcolor2 ...}} {{path/to/input.ppm}} > {{path/to/output.ppm}}"
            },
            {
                "description": "Specify how similar colors must be in order to be considered the same",
                "command": "ppmchange -closeness {{percentage}} {{oldcolor1 newcolor1 oldcolor2 newcolor2 ...}} {{path/to/input.ppm}} > {{path/to/output.ppm}}"
            },
            {
                "description": "Replace all pixels not specified in the arguments by a color",
                "command": "ppmchange {{-r|-remainder}} {{color}} {{oldcolor1 newcolor1 oldcolor2 newcolor2 ...}} {{path/to/input.ppm}} > {{path/to/output.ppm}}"
            }
        ]
    }
}