\ .\" This man page was generated by the Netpbm tool 'makeman' from HTML source. .\" Do not hand-hack it! If you have bug fixes or improvements, please find .\" the corresponding HTML page on the Netpbm website, generate a patch .\" against that, and send it to the Netpbm maintainer. .TH "Pgmtoppm User Manual" 1 "02 October 2021" "netpbm documentation" .SH NAME pgmtoppm - colorize a PGM (grayscale) image into a PPM (color) image .UN synopsis .SH SYNOPSIS \fBpgmtoppm\fP [\fB-black=\fP\fIcolorspec1\fP] [\fB-white=\fP\fIcolorspec2\fP] [\fIpgmfile\fP] \fBpgmtoppm\fP \fB-map=\fP\fIfilename\fP [\fIpgmfile\fP] \fBpgmtoppm\fP \fIcolorspec\fP [\fIpgmfile\fP] \fBpgmtoppm\fP \fIcolorspec1\fP\fB-\fP\fIcolorspec2\fP [\fIpgmfile\fP] .PP Minimum unique abbreviation of option is acceptable. You may use double hyphens instead of single hyphen to denote options. You may use white space in place of the equals sign to separate an option name from its value. .UN description .SH DESCRIPTION .PP This program is part of .BR "Netpbm" (1)\c \&. .PP If all you want to do is convert PGM to PPM, keeping the same gray pixels, you may not need to. All Netpbm programs that expect PPM input also recognize PGM. And if you must have a PPM file, use \fBppmtoppm\fP instead. It is more efficient and easier to use. .PP \fBpgmtoppm\fP reads a PGM as input and produces a PPM file as output with a specific color assigned to each gray value in the input. .PP You can specify the color in the output to which black in the input maps, and the color to which white maps. All the gray values in between map linearly (across a three dimensional space) to colors between the black and white colors you specify. .PP Use the \fB-black\fP and \fB-white\fP options for this. For historical reasons, you can alternatively use a non-option argument to specify the colors. If you do that, \fBpgmtoppm\fP interprets the color argument like this: if the argument takes the form \fIblack\fP-\fIwhite\fP, it has the effect of \fB-black=\fP\fIblack\fP \fB-white=\fP\fIwhite\fP If instead there is no hyphen in the color argument, it has the effect of \fB-white=\fP\fIcolor_argument\fP. .PP Because of the historical syntax, it is not possible to let both \fB-black\fP and \fB-white\fP default (but you shouldn't want to -- see below for advice on making such a null conversion). .PP You can alternatively specify an entire colormap with the \fB-map\fP option. .PP A more direct way to specify a particular color to replace each particular gray level is to use \fBpamlookup\fP. You make an index file that explicitly associates a color with each possible gray level. .UN options .SH OPTIONS .PP In addition to the options common to all programs based on libnetpbm (most notably \fB-quiet\fP, see .UR index.html#commonoptions Common Options .UE \&), \fBpgmtoppm\fP recognizes the following command line options: .TP \fB-black=\fP\fIcolorspec\fP The program maps black pixels in the input to this color in the output. The default is black. .sp Specify the color (\fIcolor\fP) as described for the .UR libnetpbm_image.html#colorname argument of the \fBpnm_parsecolor()\fP library routine .UE \&. .sp You cannot specify this together with \fB-map\fP. .sp This option was new in Netpbm 10.97 (December 2021). Before that, use the color argument. .TP \fB-white=\fP\fIcolorspec\fP The program maps white pixels in the input to this color in the output. The default is white. .sp Specify the color (\fIcolor\fP) as described for the .UR libnetpbm_image.html#colorname argument of the \fBpnm_parsecolor()\fP library routine .UE \&. .sp You cannot specify this together with \fB-map\fP. .sp This option was new in Netpbm 10.97 (December 2021). Before that, use the color argument. .TP \fB-map=\fP\fIfilename\fP This option specifies a complete mapping of gray values in the input to color values in the output. The map file (named \fIfilename\fP) is just a \fBppm\fP file; it can be any shape, all that matters is the colors in it and their order. In this case, black gets mapped into the first color in the map file, and white gets mapped to the last and gray values in between are mapped linearly onto the sequence of colors in between. The maxval of the output image is the maxval of the map image. .UN maxval .SH NOTE - MAXVAL .PP When you don't use \fB-map\fP, the "maxval," or depth, of the output image is the same as that of the input image. The maxval affects the color resolution, which may cause quantization errors you don't anticipate in your output. For example, you have a simple black and white image as a PGM with maxval 1. Run this image through \fBpgmtoppm 0f/00/00\fP to try to make the image black and faint red. Because the output image will also have maxval 1, there is no such thing as faint red. It has to be either full-on red or black. \fBpgmtoppm\fP rounds the color 0f/00/00 down to black, and you get an output image that is nothing but black. .PP The fix is easy: Pass the input through \fBpamdepth\fP on the way into \fBpgmtoppm\fP to increase its depth to something that would give you the resolution you need to get your desired color. In this case, \fBpamdepth 16\fP would do it. Or spare yourself the unnecessary thinking and just say \fBpamdepth 255\fP. .PP PBM input is a special case. While you might think this would be equivalent to a PGM with maxval 1 since only two gray levels are necessary to represent a PBM image, \fBpgmtoppm\fP, like all Netpbm programs, in fact treats it as a maxval of 255. .UN seealso .SH SEE ALSO .BR "ppmtoppm" (1)\c \&, .BR "pamdepth" (1)\c \&, .BR "rgb3toppm" (1)\c \&, .BR "ppmtopgm" (1)\c \&, .BR "ppmtorgb3" (1)\c \&, .BR "ppm" (1)\c \&, .BR "pgm" (1)\c \& .UN author .SH AUTHOR Copyright (C) 1991 by Jef Poskanzer. .SH DOCUMENT SOURCE This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at .IP .B http://netpbm.sourceforge.net/doc/pgmtoppm.html .PP