pnmtopng
pnmtopng(1) pnmtopng(1)NAME
pnmtopng - convert a portable anymap into a Portable Net work Graphics fileSYNOPSIS
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 automatically scale colors to have a maxval of 255 or 65535. Grayscale files will be pro duced 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 create 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 Allows to make one particular color fully transpar ent. The format to specify the color is either (when for example orange) "1.0,0.5,0.0", where the values are floats between zero and one, or with the syntax "#RGB", "#RRGGBB" or "#RRRRGGGGBBBB" where R, G and B are hexa-decimal numbers. -background color To create a background color chunck in the png- file, which can be used for subsequent alpha-chan nel or transparent-color conversions. See -trans parent for format of color. -gamma value Creates an gAMA chunk. By providing the gamma-value of the pnm-file the software that lateron will dis play 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 Use this parameter to create a chunk that specifies the frequency (or histogram) of 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 fol lows: 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 cur rent 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 com pressed. -time yy-mm-dd hh:mm:ss or -time yyyy-mm-dd hh:mm:ss This option allows you to specify the (modifica tion)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 between 0 for no compression (max speed) and 9 for maximum compres sion. -force When set, -force limits the optimizations of pnm topng. A png-file similar to the pnm-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 pre fix.SEE ALSO
pngtopnm(1), gif2png(1), pnmgamma(1), pnm(5) 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 opti mizing.AUTHORS
Copyright (C) 1995-1997 by Alexander Lehmann and Willem van Schaik. 6 January 1997 pnmtopng(1)