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CentOS 7.0 - man page for pamrubber (centos section 0)

PamRubber User Manual(0)						 PamRubber User Manual(0)

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">

NAME
       pamrubber - a rubber-sheeting utility that stretches an image based on control points

SYNOPSIS
       pamrubber  {-tri  |  -quad}  [-linear] [-frame] [-randomseed=N] cp1x cp1y [cp2x cp2y [cp3x
       cp3y [cp4x cp4y]]] cp1x cp1y [cp2x cp2y [cp3x cp3y [cp4x cp4y]]] [filename]

       Minimum unique abbreviation of options is acceptable.  You may use double hyphens  instead
       of single hyphen to denote options.

DESCRIPTION
       This program is part of Netpbm(1)

       The  pamrubber  utility	converts  a  pam  image  into a new image with the contents moved
       around.	The transformation is often called 'rubber sheeting': you identify control points
       (CP)  on  the  source  image  and specify new positions for those points in the new image.
       pamrubber moves all the pixels around, stretching and compressing as necessary, as if  the
       original  image	were on a sheet of rubber and you pulled on the sheet to make the control
       points move to their new locations.

       The new image has the same dimensions and format as the original.

       The transformation can happen in two very different ways, called 'quad'	and  'tri.'  With
       the  former, you must specify four control points (for both source and target).	These are
       the corners of two quadrilaterals that will act as the coordinate system for  both  source
       and  target images.  Consider them as non-orthogonal (0,0), (0,1), (1,0) and (1,1) points.
       This transformation comes close to the one pamperspective does, however that program  does
       other corrections as well.

       When  you  specify  less  than four control points, the program adds control points in the
       following way.  With three control points, pamrubber chooses the fourth one such that  the
       four  points form a parallelogram.  With two points, pamrubber considers them the opposite
       corners of a rectangle.	When you specify only one control point, pamrubber uses a rectan-
       gle from the top left corner of the image to the single control point.

       In  'tri' mode, pamrubber conceptually cuts up the source and target image into triangles.
       It Transforms within each corresponding pair of triangles in a stretching  fashion.   It's
       like pulling on the three corners of the triangle.  In this mode, each pixel in the source
       image gets mapped to a position in the target image. No pixels are lost.

       When, in 'tri' mode, you specify only a single control point  in  the  source  and  target
       image,  pamrubber creates four triangles from this point to the four corners of the image.
       With two points, the program creates six triangles from the two endpoints of the line con-
       necting the two points, again to the four corners of the image. Three control points is in
       a way the core of this utility in 'tri' mode.  Between the three edges of the central tri-
       angle and the four edges of the image, pamrubber constructs another seven triangles.  Four
       control points define two central connected triangles.  In total this results  in  cutting
       the source and target image up into ten triangles.

       In  this  case  clearly	a  picture says more than a thousand words.  There is a graphical
       illustration of these various modes at
	www.schaik.com/netpbm/rubber <http://www.schaik.com/netpbm/rubber> .  An example  of  how
       to use this type of rubber sheeting in cartography is in the article
	Visualizing	      the	   Landscape	      of	  Old-Time	    Tokyo
       <http://www.isprs.org/proceedings/XXXVI/5-W1/papers/21.pdf> .

PARAMETERS
       The parameters are control points (cp) in pairs of x and y.  The source and  target  image
       must  have the same number of control points.  The minimum number of values specified here
       is 4 for a single control point in the source and target image.	The  maximum  is  16  for
       four control points in each image.

       filename  is  the  name	of the input file. If you don't specify this, pamrubber reads the
       image from Standard Input.

OPTIONS
       <dl compact="compact">

       -tri | -quad

	      This selects the type of rubber sheeting done.  You must	specify  exactly  one  of
	      these options.

       -linear

	      This  determines	whether pamrubber uses nearest neighbor interpolation or bilinear
	      interpolation of four source pixels.

       -frame

	      This option causes pamrubber to overlay the target image	with  the  edges  of  the
	      quadrilaterals,  respectively  the  triangles used for the rubber sheeting.  To get
	      the same overlay for the source image, use a pamrubber transformation with  identi-
	      cal control points for source and target.

       -randomseed=N

	      pamrubber  randomizes  some  of  its  output.   So  that you can produce repeatable
	      results, you can choose the seed of the random number generator with  this  option.
	      If  you  use  the  same  input image and the same random number generator seed, you
	      should always get the exact same output.	By default, pamrubber uses  the  time  of
	      day  as  the  seed,  so  you get slightly different output when you run the program
	      twice on the same input.

	      Before Netpbm 10.61 (December 2012), this was  called  -randseed,  and  that  still
	      works.

SEE ALSO
       pam(1)
	and pamperspective(1)

HISTORY
       pamrubber was new in Netpbm 10.54 (March 2011).

AUTHORS
       Willem van Schaik wrote this program in February 2011 and contributed it to Netpbm.

netpbm documentation			  February 2011 		 PamRubber User Manual(0)


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