pngtopnm

pngtopnm

NAME SYNOPSIS DESCRIPTION OPTIONS SEE ALSO NOTE BUGS AUTHORS

NAME

pngtopnm - convert a Portable Network Graphics file into a portable anymap

SYNOPSIS

pngtopnm [-verbose [-alpha [unrenderable node] [-gamma value [-text file [-time [''pngfile''

DESCRIPTION

Reads a Portable Network Graphics as input. Produces a portable anymap as output. The type of the output file depends on the input file - if it's black pbm file is written, else if it's grayscale a pgm file, else a ppm'' file.

OPTIONS

-verbose

Display the format of the input file and the type of the output file. If the chunks are part of the png-file, the alpha, transparency and gamma-values will be indicated.

-alpha

Output the alpha channel or transparency mask of the image. The result is either a pbm file or pgm file, depending on whether different levels of transparency appear.

-mix

Compose the image with the transparency or alpha mask against a the background. When a background chunk is available that color is taken, else black will do.

-background color

If no background color chunck is present in the png-file, or when another color is required this parameter can be used to set the background color of images. This is especially useful for alpha-channel images or those with transparency chunks. The format, to specify the color in, is either (in the case of orange) ''

-gamma value

Converts the image to a new display-gamma value. When a gAMA chunk is present in the png-file, the image-gamma value will be used. When not, the image-gamma is considered to be 1.0. Based on the image-gamma and the display-gamma given with this option the colors written to the pnm-file will be adjusted. Because the gamma's of uncompensated monitors are around 2.6, which results in an image-gamma of 0.45, some typical situations are: when the image-gamma is 0.45 (use -verbose to check) and the picture is too light, your system is gamma-corrected, so convert with

-text file

Writes the tEXt and zTXt chunks to a file, in a format as described in the pnmtopng man-page. These chunks contain text comments or annotations.

-time

Prints the tIME chunk to stderr.

All flags can be abbreviated to their shortest unique prefix.

SEE ALSO

pnmtopng(1), ptot(1), pnmgamma(1), pnm(5)

NOTE

Instead of pngtopnm|pnmtoxxx, a specific converter should be used, if available. E.g. ptot (PNG to TIFF 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.