pfilt(1) manual page

Table of Contents

Pfilt performs anti-aliasing and scaling on a RADIANCE picture. The program makes two passes on the picture file in order to set the exposure to the correct average value. If no file is given, the standard input is read.

-x res: Set the output x resolution to res. This must be less than or equal to the x dimension of the target device. If res is given as a slash followed by a real number, the input resolution is divided by this number to get the output resolution. By default, the output resolution is the same as the input.

-y res: Set the output y resolution to res, similar to the specification of the x resolution above.

-p rat: Set the pixel aspect ratio to rat. Either the x or the y resolution will be reduced so that the pixels have this ratio for the specified picture. If rat is zero, then the x and y resolutions will adhere to the given maxima. Zero is the default.

-c: Pixel aspect ratio is being corrected, so do not write PIXASPECT variable to output file.

-e exp: Adjust the exposure. If exp is preceded by a `+' or `-', the exposure is interpreted in f-stops (ie. the power of two). Otherwise, exp is interpreted as a straight multiplier. The individual primaries can be changed using -er, -eg and -eb. Multiple exposure options have a cumulative effect.

-t lamp: Color-balance the image as if it were illuminated by fixtures of the given type. The specification must match a pattern listed in the lamp lookup table (see the -f option below).

-f lampdat: Use the specified lamp lookup table rather than the default (lamp.tab).

-1: Use only one pass on the file. This allows the exposure to be controlled absolutely, without any averaging. Note that a single pass is much quicker and should be used whenever the desired exposure is known and star patterns are not required.

-2: Use two passes on the input. This is the default.

-b: Use box filtering (default). Box filtering averages the input pixels corresponding to each separate output pixel.

-r rad: Use Gaussian filtering with a radius of rad relative to the output pixel size. This option with a radius around 1 and a reduction in image width and height of 2 or 3 produces the highest quality pictures. A radius greater than 1 results in a defocused picture.

-m frac: Limit the influence of any given input pixel to frac of any given output pixel. This option may be used to mitigate the problems associated with inadequate image sampling, at the expense of a slightly blurred image. The fraction given should not exceed the output picture dimensions over the input picture dimensions (x_o*y_o/x_i/y_i), or blurring will occur over the entire image. This option implies the -r option for Gaussian filtering, which defaults to a radius of 1.

-h lvl: Set intensity considered ``hot'' to lvl. This is the level above which areas of the image will begin to exhibit star diffraction patterns (see below). The default is 100 watts/sr/m2.