pnmrotate(1) [minix man page]
pnmrotate(1) General Commands Manual pnmrotate(1) NAME
pnmrotate - rotate a portable anymap by some angle SYNOPSIS
pnmrotate [-noantialias] angle [pnmfile] DESCRIPTION
Reads a portable anymap as input. Rotates it by the specified angle and produces a portable anymap as output. If the input file is in color, the output will be too, otherwise it will be grayscale. The angle is in degrees (floating point), measured counter-clockwise. It can be negative, but it should be between -90 and 90. Also, for rotations greater than 45 degrees you may get better results if you first use pnmflip to do a 90 degree rotation and then pnmrotate less than 45 degrees back the other direction The rotation algorithm is Alan Paeth's three-shear method. Each shear is implemented by looping over the source pixels and distributing fractions to each of the destination pixels. This has an "anti-aliasing" effect - it avoids jagged edges and similar artifacts. However, it also means that the original colors or gray levels in the image are modified. If you need to keep precisely the same set of colors, you can use the -noantialias flag. This does the shearing by moving pixels without changing their values. If you want anti-aliasing and don't care about the precise colors, but still need a limited *number* of colors, you can run the result through ppmquant. All flags can be abbreviated to their shortest unique prefix. REFERENCES
"A Fast Algorithm for General Raster Rotation" by Alan Paeth, Graphics Interface '86, pp. 77-81. SEE ALSO
pnmshear(1), pnmflip(1), pnm(5), ppmquant(1) AUTHOR
Copyright (C) 1989, 1991 by Jef Poskanzer. 12 January 1991 pnmrotate(1)
Check Out this Related Man Page
pnmalias(1) General Commands Manual pnmalias(1) NAME
pnmalias - antialias a portable anyumap. SYNOPSIS
pnmalias [-bgcolor color] [-fgcolor color] [-bonly] [-fonly] [-balias] [-falias] [-weight w] [pnmfile] DESCRIPTION
Reads a portable anymap as input, and applies anti-aliasing to background and foreground pixels. If the input file is a portable bitmap, the output anti-aliased image is promoted to a graymap, and a message is printed informing the user of the change in format. OPTIONS
-bgcolor colorb, -fgcolor colorf set the background color to colorb, and the foreground to color to colorf. Pixels with these values will be anti-aliased. by default, the background color is taken to be black, and foreground color is assumed to be white. The colors can be specified in five ways: o A name, assuming that a pointer to an X11-style color names file was compiled in. o An X11-style hexadecimal specifier: rgb:r/g/b, where r g and b are each 1- to 4-digit hexadecimal numbers. o An X11-style decimal specifier: rgbi:r/g/b, where r g and b are floating point numbers between 0 and 1. o For backwards compatibility, an old-X11-style hexadecimal number: #rgb, #rrggbb, #rrrgggbbb, or #rrrrggggbbbb. o For backwards compatibility, a triplet of numbers separated by commas: r,g,b, where r g and b are floating point numbers between 0 and 1. (This style was added before MIT came up with the similar rgbi style.) Note that even when dealing with graymaps, background and foreground colors need to be specified in the fashion described above. In this case, background and foreground pixel values are taken to be the value of the red component for the given color. -bonly, -fonly Apply anti-aliasing only to background (-bonly), or foreground (-fonly) pixels. -balias, -falias Apply anti-aliasing to all pixels surrounding background (-balias), or foreground (-falias) pixels. By default, anti-aliasing takes place only among neighboring background and foreground pixels. -weight w Use w as the central weight for the aliasing filter. W must be a real number in the range 0 < w < 1. The lower the value of w is, the "blurrier" the output image is. The default is w = 1/3. SEE ALSO
pbmtext(1), pnmsmooth(1), pnm(5) AUTHOR
Copyright (C) 1992 by Alberto Accomazzi, Smithsonian Astrophysical Observatory. 30 April 1992 pnmalias(1)