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.\" RCSid "$Id: pcomb.1,v 1.6 2005/03/01 22:55:21 greg Exp $" |
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.TH PCOMB 1 8/31/96 RADIANCE |
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.SH NAME |
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pcomb - combine RADIANCE pictures |
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.SH SYNOPSIS |
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.B pcomb |
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[ |
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.B -h |
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][ |
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.B -w |
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][ |
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.B "\-x xres" |
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][ |
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.B "\-y yres" |
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][ |
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.B "\-f file" |
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][ |
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.B "\-e expr" |
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] |
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[ |
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[ |
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.B -o |
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][ |
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.B "\-s factor" |
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][ |
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.B "\-c r g b" |
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] |
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.B "input .." |
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] |
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.SH DESCRIPTION |
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.I Pcomb |
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combines equal-sized RADIANCE pictures and sends the result to the |
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standard output. |
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By default, the result is just a linear combination of |
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the input pictures multiplied by |
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.I \-s |
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and |
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.I \-c |
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coefficients, |
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but an arbitrary mapping can be assigned with the |
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.I \-e |
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and |
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.I \-f |
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options. |
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Negative coefficients and functions are allowed, and |
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.I pcomb |
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will produce color values of zero where they would be negative. |
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.PP |
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The variables |
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.I ro, |
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.I go |
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and |
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.I bo |
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specify the red, green and blue output values, respectively. |
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Alternatively, the single variable |
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.I lo |
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can be used to specify a brightness value for black and white output. |
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The predefined functions |
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.I ri(n), |
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.I gi(n) |
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and |
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.I bi(n) |
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give the red, green and blue input values for |
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picture |
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.I n. |
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To access a pixel that is nearby the current one, these functions |
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also accept optional x and y offsets. |
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For example, |
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.I ri(3,-2,1) |
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would return the red component of the pixel from picture 3 |
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that is left 2 and up 1 from the current position. |
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Although x offsets may be as large as width of the picture, |
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y offsets are limited to a small window (+/- 32 pixels) due to efficiency |
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considerations. |
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However, it is not usually necessary to worry about this problem -- |
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if the requested offset is not available, the next best pixel is |
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returned instead. |
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.PP |
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For additional convenience, the function |
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.I li(n) |
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is defined as the input brightness for picture |
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.I n. |
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This function also accepts x and y offsets. |
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.PP |
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The constant |
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.I nfiles |
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gives the number of input files present, |
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and |
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.I WE |
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gives the white efficacy (lumens/brightness) for pixel values, |
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which may be used with the |
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.I \-o |
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option or the le(n) values to convert to absolute |
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photometric units (see below). |
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The variables |
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.I x |
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and |
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.I y |
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give the current output pixel location for use in |
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spatially dependent functions, the constants |
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.I xmax |
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and |
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.I ymax |
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give the input resolution, and the constants |
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.I xres |
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and |
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.I yres |
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give the output resolution (usually the same, but see below). |
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The constant functions |
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.I "re(n), ge(n), be(n)," |
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and |
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.I le(n) |
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give the exposure values for picture |
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.I n, |
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and |
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.I pa(n) |
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gives the corresponding pixel aspect ratio. |
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Finally, for pictures with stored view parameters, |
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the functions |
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.I "Ox(n), Oy(n)" |
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and |
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.I Oz(n) |
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return the ray origin in world coordinates for the current pixel |
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in picture |
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.I n, |
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and |
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.I "Dx(n), Dy(n)" |
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and |
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.I Dz(n) |
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return the normalized ray direction. |
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In addition, the function |
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.I T(n) |
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returns the distance from the origin to the aft clipping plane |
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(or zero if there is no aft plane), and the function |
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.I S(n) |
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returns the solid angle of the current pixel in steradians |
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(always zero for parallel views). |
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If the current pixel is outside the view region, |
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.I T(n) |
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will return a negative value, and |
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.I S(n) |
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will return zero. |
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.PP |
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The |
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.I \-h |
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option may be used to reduce the information header size, which |
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can grow disproportionately after multiple runs of |
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.I pcomb |
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and/or |
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.I pcompos(1). |
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The |
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.I \-w |
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option can be used to suppress warning messages about invalid |
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calculations. |
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The |
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.I \-o |
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option indicates that original pixel values are to be used for the next |
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picture, undoing any previous exposure changes or color correction. |
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.PP |
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The |
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.I \-x |
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and |
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.I \-y |
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options can be used to specify the desired output resolution, |
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.I xres |
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and |
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.I yres, |
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and can be expressions involving other constants such as |
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.I xmax |
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and |
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.I ymax. |
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The constants |
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.I xres |
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and |
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.I yres |
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may also be specified in a file or expression. |
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The default output resolution is the same as the input resolution. |
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.PP |
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The |
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.I \-x |
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and |
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.I \-y |
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options must be present if there are no input files, when |
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the definitions of |
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.I ro, |
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.I go |
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and |
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.I bo |
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will be used to compute each output pixel. |
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This is useful for producing simple test pictures for various |
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purposes. |
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(Theoretically, one could write a complete renderer using just the |
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functional language...) |
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.PP |
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The standard input can be specified with a hyphen ('-'). |
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A command that produces a RADIANCE picture can be given in place of a file |
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by preceeding it with an exclamation point ('!'). |
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.SH EXAMPLES |
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To produce a picture showing the difference between pic1 and pic2: |
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.IP "" .2i |
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pcomb -e 'ro=ri(1)-ri(2);go=gi(1)-gi(2);bo=bi(1)-bi(2)' pic1 pic2 > diff |
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.PP |
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Or, more efficiently: |
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.IP "" .2i |
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pcomb pic1 -s -1 pic2 > diff |
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.PP |
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To precompute the gamma correction for a picture: |
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.IP "" .2i |
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pcomb -e 'ro=ri(1)^.4;go=gi(1)^.4;bo=bi(1)^.4' pic > pic.gam |
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.PP |
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To perform some special filtering: |
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.IP "" .2i |
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pcomb -f myfilt.cal -x xmax/2 -y ymax/2 input.pic > filtered.pic |
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.PP |
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To make a picture of a dot: |
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.IP "" .2i |
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pcomb -x 100 -y 100 -e 'ro=b;go=b;bo=b;b=if((x-50)^2+(y-50)^2-25^2,0,1)' > dot |
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.SH AUTHOR |
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Greg Ward |
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.SH "SEE ALSO" |
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getinfo(1), icalc(1), pcompos(1), pfilt(1), rpict(1) |