# pnmtopng(1) - man - phpMan [pnmtopng(1)](https://www.chedong.com/phpMan.php/man/pnmtopng/1/markdown) General Commands Manual [pnmtopng(1)](https://www.chedong.com/phpMan.php/man/pnmtopng/1/markdown) ## NAME pnmtopng - convert a portable anymap into a Portable Network Graphics file ## SYNOPSIS **pnmtopng** [-verbose] [-downscale] [-interlace] [-alpha file] [-transparent [=]color] [-background color] [-gamma value] [-hist] [-chroma wx wy rx ry gx gy bx by] [-phys x y unit] [-text file] [-ztxt file] [-time [yy]yy-mm-dd hh:mm:ss] [-filter type] [-compression level] [-force] [_pnmfile_] ## DESCRIPTION Reads a portable pixmap as input. Produces a Portable Network Graphics file as output. Color values in PNG files are either eight or sixteen bits wide, so _pnmtopng_ will automati‐ cally scale colors to have a maxval of 255 or 65535. Grayscale files will be produced with bit depths 1, 2, 4, 8 or 16. An extra _pnmdepth_ step is not necessary. ## OPTIONS ### -verbose Display the format of the output file. ### -downscale Enables scaling of maxvalues of more then 65535 to 16 bit. Since this means loss of image data, the step is not performed by default. ### -interlace Creates an interlaced PNG file (Adam7). ### -alpha file The alpha channel of pixel (or image) specifies the transparency of a pixel. To cre‐ ate this fourth pixel value a separate _.pbm-_ or _.pgm-file_ is needed. In this file black (0) stands for fully transparant and white (1) will become opaque. The sizes of both pbm/pgm/ppm-files must be the same. If the information contained in the alpha mask can also be represented as a transparency index, it will be used, since this should result in a smaller image file. ### -transparent color **ppmtogif** marks the specified color as transparent in the PNG image. You specify the color as in [**ppmmake**(1)](https://www.chedong.com/phpMan.php/man/ppmmake/1/markdown).**E.g.** **red** or **rgb:ff/00/0d**. If the color you specify is not present in the image, **pnmtopnm** selects instead the color in the image that is closest to the one you specify. Closeness is measured as a cartesian distance between colors in RGB space. If multiple colors are equidistant, **pnmtopnm** chooses one of them arbitrarily. However, if you prefix your color specification with "=", e.g. **-transparent** **=red** Only the exact color you specify will be transparent. If that color does not appear in the image, there will be no transparency. **pnmtopng** issues an information message when this is the case. ### -background color To create a background color chunck in the _png-file,_ which can be used for subsequent alpha-channel or transparent-color conversions. See -transparent for format of color. ### -gamma value Creates an gAMA chunk. By providing the gamma-value of the _pnm-file_ the software that lateron will display the _png-file_ will be able to do the necessary gamma-corrections. A good rule-of-thumb is that when the file is created by a software program (like a CAD-program or a ray-tracer) the value is probably 1.0. When the _pnm-file_ looks good on a non-gamma corrected PC display (which has itself a gamma-value of 2.2 - 2.8), a value of 0.45 should be given. ### -hist the colors in the image. ### -chroma white point X and Y, red X and Y, green X and Y, and blue X and Y To specify the white point and rgb values following the CIE-1931 spec. ### -phys x y unit When your image should not be displayed with square but with rectangular pixels this option should be used to create a pHYS chunk. When the unit-value is 0 the x and y only gives the ratio of pixel width and height. When it is 1 the x and y specify the number of pixels per meter. ### -text file Allows to include comments in the text-chunk of the _png-file._ The format of the text- file is as follows: when the first column does not contain a blank or a tab, the first word is considered to be the keyword. For keywords to contain spaces, enclose them in double-quotes. When the first character on a line is a blank or tab, the rest of the line is a new line of the current comment. Note that the initial spaces are not considered to be part of the comment line. Here is an example: ------------------------------------------- Title PNG-file Author your name Description how to include a text-chunk into a PNG file "Creation date" 3-feb-1987 Software pnmtopng ------------------------------------------- ### -ztxt file The same as -text, but now the text will be compressed. ### -time yy-mm-dd hh:mm:ss or -time yyyy-mm-dd hh:mm:ss This option allows you to specify the (modification)time. The year parameter can be given as a two- or a four-digit value. ### -filter type When the types of filters must be restricted you can specify here which filter you want to use. Allowed values are: 0 (none), 1 (sub), 2 (up), 3 (avg) and 4 (paeth). ### -compression level To explicitly set the compression level of zlib use this parameter. Select a level be‐ tween 0 for no compression (max speed) and 9 for maximum compression. ### -force input is as much as possible enforced. For example no paletted files will be created and alpha-channel images will not be converted to images with a transparency chunck. All flags can be abbreviated to their shortest unique prefix. ## SEE ALSO [pngtopnm(1)](https://www.chedong.com/phpMan.php/man/pngtopnm/1/markdown), [gif2png(1)](https://www.chedong.com/phpMan.php/man/gif2png/1/markdown), [pnmgamma(1)](https://www.chedong.com/phpMan.php/man/pnmgamma/1/markdown), [pnm(5)](https://www.chedong.com/phpMan.php/man/pnm/5/markdown) ## NOTE Instead of xxxtopnm|pnmtopng, a specific converter should be used, if available. E.g. _gif2png_ (GIF conversion), etc. ## BUGS There could be an option to read the comment text from pnm comments instead of a separate file. The program could be much faster, with a bit of code optimizing. ## AUTHORS Copyright (C) 1995-1997 by Alexander Lehmann and Willem van Schaik. 6 January 1997 [pnmtopng(1)](https://www.chedong.com/phpMan.php/man/pnmtopng/1/markdown)