# ppmhist - print a histogram of the colors in a PPM image - man(1) - [phpMan] > **TLDR:** Print a histogram of the colors present in a PPM image. > - Generate the histogram for human reading: `ppmhist {{-nom|-nomap}} {{path/to/image.ppm}}` - Generate a PPM file of the colormap for the image, with the color histogram as comments: `ppmhist {{-m|-map}} {{path/to/image.ppm}}` - Display version: `ppmhist {{-v|-version}}` *Source: tldr-pages* --- _Ppmhist_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown) General Commands Manual _Ppmhist_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown) ## NAME ppmhist - print a histogram of the colors in a PPM image ## SYNOPSIS **ppmhist **[**-hexcolor **| **-float **| **-colorname **| **-map**] [**-nomap**] [**-noheader**] [**-sort=**{**frequency**,**rgb**}] [**-forensic**] [_ppmfile_] ## DESCRIPTION This program is part of [**Netpbm**(1)](https://www.chedong.com/phpMan.php/man/Netpbm/1/markdown). **ppmhist **reads a PPM image as input and generates a histogram of the colors in the image, i.e. a list of all the colors and how many pixels of each color are in the image. ### Output Format The output is in one of two basic formats: a report for humans and a PPM image for use by programs. The PPM image is actually quite readable by humans too. ### Human Report You get this format by specifying (or defaulting to) the **-nomap **option. The format is one line for each color in the input image. By default, there are two lines of column header and a summary at the top. Use the **-noheader** option to suppress those lines. The summary tells you whether black or white are present and how many shades of gray and color are present. The summary was new in Netpbm 10.82 (March 2018). In each line, **ppmhist **identifies the color by red, green, and blue components. By default, it lists each of these in decimal, using the exact values that are in the PPM input. So if the image has a maxval of 255, the numbers in the listing range from 0 to 255. With the ### -hexcolor -float numbers are fractional, adjusted to a maxval of 1. Each line lists the luminosity of the color. It is in decimal on the same scale as the rgb values (see above). Each line lists the number of pixels in the image that have the color. This is in decimal. ### PPM Output You get this format with the **-map **option. The output file is a genuine PPM image, but it is PPM Plain format and contains comments so that it is not a lot different from the human report described above. As a PPM image, it can be useful as input to other programs that need some kind of palette. The image is a single row with one column for each distinct color in the image. The function of PPM output is essentially the same as the output of **pnmcolormap all**. **ppmhist** is much older than **pnmcolormap**. ## OPTIONS In addition to the options common to all programs based on libnetpbm (most notably **-quiet**, see [ Common Options](index.html#commonoptions) ), **ppmhist **recognizes the following command line options: ### -sort= The **-sort **option determines the order in which the colors are listed in the output. **rgb **means to sort them first by the intensity of the red component of the color, then of the green, then of the blue, with the least intense first. **frequency **means to list them in order of how many pixels in the input image have the color, with the most rep‐ resented colors first. Among colors with the same frequency, the order is the same as with **rgb**. The default is **frequency**. Before Netpbm 10.88 (September 2019), with **-sort=frequency**, the order of colors that have the same frequency is arbitrary. ### -hexcolor Print the color components in hexadecimal. See [output format](#output) . You may not specify this option along with **-float **or **map**. ### -float [0,1]. See [output format](#output) . You may not specify this option along with **-hexcolor **or **map**. This option was added in Netpbm 10.19 (November 2003). ### -map ments. See [output format](#output) . You may not specify this option along with **-float **or **hexcolor**. ### -nomap ### -colorname Add the color name to the output. This is the name from the [system color dictionary](libppm.html#dictionary) . If the exact color is not in the color dictionary, it is the closest color that is in the dictionary and is preceded by a '*'. If you don't have a system color dictionary, the program fails. This option was added in Netpbm 10.10 (October 2002). ### -noheader Do not print the column headings. ### -forensic With this option, **ppmhist **works on images that contain invalid sample values. Nor‐ mally, like most Netpbm programs, **ppmhist **fails if it encounters a sample value greater than the maxval that the image declares. The presence of such a value means the image is invalid, so the pixels have no meaning. But with **-forensic**, **ppmhist **pro‐ duces a histogram of the actual sample values without regard to maxval. It issues messages summarizing the invalid pixels if there are any. One use for this is to diagnose the problem that caused the invalid Netpbm image to exist. There is a small exception to the ability of **ppmhist **to process invalid pixels even with **-forensic**: it can never process a sample value greater than 65535. Note that in the rarely used Plain PPM format, it is possible for a number greater than that to ap‐ pear where a sample value belongs. This option was new in Netpbm 10.66 (March 2014). But Netpbm older than 10.66 does not properly reject invalid sample values, so the effect is very similar to **-forensic**. ## SEE ALSO [**ppm**(1)](https://www.chedong.com/phpMan.php/man/ppm/1/markdown), [**pgmhist**(1)](https://www.chedong.com/phpMan.php/man/pgmhist/1/markdown), [**pnmcolormap**(1)](https://www.chedong.com/phpMan.php/man/pnmcolormap/1/markdown), [**pnmhistmap**(1)](https://www.chedong.com/phpMan.php/man/pnmhistmap/1/markdown), [**ppmchange**(1)](https://www.chedong.com/phpMan.php/man/ppmchange/1/markdown) ## AUTHOR Copyright (C) 1989 by Jef Poskanzer. ## DOCUMENT SOURCE This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at **** netpbm documentation 24 August 2019 _Ppmhist_ _User_ [_Manual_(1)](https://www.chedong.com/phpMan.php/man/Manual/1/markdown)