Section: User Commands (1)
Updated: 6 January 1997
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]
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 produced with bit depths 1, 2, 4, 8 or 16. An extra pnmdepth step is not necessary.
You specify the color as in ppmmake?(1).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.
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.
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:
Author your name
Description how to include a text-chunk
into a PNG file
"Creation date" 3-feb-1987
There could be an option to read the comment text from pnm comments instead of a separate file.
Copyright (C) 1995-1997 by Alexander Lehmann
and Willem van Schaik.
Tutoriais de Tecnologia Web