


IMROLL(1IM)                IMAGE TOOLS                IMROLL(1IM)



NAME
     imroll  -  Rolls images vertically and/or horizontally

SYNOPSIS
     imroll [_o_p_t_i_o_n_s] _i_n_f_i_l_e_n_a_m_e _o_u_t_f_i_l_e_n_a_m_e

DESCRIPTION
     imroll reads each image in the input file, rolls  it  verti-
     cally,  horizontally,  or both, then writes it to the output
     file.  The input and output image file formats may  be  dif-
     ferent.

OPTIONS
     imroll has a  variety  of  options  in  the  following  five
     categories:

          File Selection     What input and output files to use
          Format Selection   What image file format to use
          Format Control     What variant of a file format to generate
          Standard           Standard generic options on all SDSC tools
          Rolling            How the image can be rolled

     _F_i_l_e _S_e_l_e_c_t_i_o_n, _F_o_r_m_a_t _S_e_l_e_c_t_i_o_n, _F_o_r_m_a_t _C_o_n_t_r_o_l, and  _S_t_a_n_-
     _d_a_r_d options are common to all SDSC image tools and are dis-
     cussed in depth in the man page for imconv(1IM).

     All options can be abbreviated to the first few unique char-
     acters.

  Rolling Options
     Rolling an image copies pixel (0,0) to  pixel  (x,y),  pixel
     (1,0) to (x+1,y), pixel (2,0) to (x+2,y), and so on.  Pixels
     that fall off the image edges wrap around  to  the  opposite
     edge.   The  effect is to slide an image horizontally and/or
     vertically, wrapping around in a cyclical fashion.

     -xroll _v_a_l_u_e

          Rolls the image horizontally by _v_a_l_u_e pixels.  Positive
          values  of  _v_a_l_u_e  roll  left-to-right, negative values
          roll right-to-left.

     -yroll _v_a_l_u_e

          Rolls the image vertically by _v_a_l_u_e  pixels.   Positive
          values  of  _v_a_l_u_e  roll  top-to-bottom, negative values
          roll bottom-to-top.

     -xroll and -yroll may be given in combination  in  order  to
     roll in both the X and Y directions simultaneously.





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IMROLL(1IM)                IMAGE TOOLS                IMROLL(1IM)



NOTES
     Image rolling may be  used  for  a  variety  of  simple  pan
     effects,  such  as  cyclical  backgrounds for cartoon chase-
     sequence animations.

     Image rolling may also be used in the processing of  scanned
     or  generated  texture images prior to repeated side-by-side
     texture mapping, such as for grassy planes, carpeted  areas,
     or brick or stone walls.  In each of these cases, the origi-
     nal texture image will be repeated over a  large  area  with
     the  left edge of one copy butting up against the right edge
     of the next copy, and the top edge of one  copy  butting  up
     against  the bottom edge of the next.  To avoid obvious grid
     lines in texturing, it is important that the left and  right
     edges,  and  top and bottom edges, of the texture match each
     other.  This may be done by bringing the image into a  paint
     system and adjusting the pixels to make them match.

     However, it is hard to visually match the left  edge  of  an
     image  with  its  right edge when those edges aren't next to
     each other.  imroll may be used to bring them next  to  each
     other.   Roll  the  image half the image's width and height.
     This places the left-right and top-bottom edges next to each
     other in the middle of the image.  Now, bring the image into
     a paint system and smear the joining line.  The  image  will
     then be ready for seamless, side-by-side texture mapping.

     For notes regarding  file  format  conversion  and  standard
     image tool options, see the man page on imconv(1IM).

     Error messages are reported to stderr.

     With no roll arguments, the actions of imroll default to the
     same  as  the SDSC image format conversion tool imconv(1IM),
     but they take a little longer.

EXAMPLES
     Roll a Wavefront RLB file 30 pixels to the right  and  store
     the result into an SGI RGB file:

          imroll original.rlb -xroll 30 rolled.rgb

     Roll a Sun raster file 100 pixels to the left and 50  pixels
     down:

          imroll incoming.ras -xroll -100 -yroll 50 outgoing.ras

SEE ALSO
     imcltroll  (1IM),  imcopy  (1IM),  imrotate  (1IM),  imshear
     (1IM), imscale (1IM), ImVfbRoll (3IM)

     For information on SDSC's image library, see imintro(3IM).



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IMROLL(1IM)                IMAGE TOOLS                IMROLL(1IM)



     For information on the individual image  file  formats,  see
     their  respective man pages: imbmp (3IM), imcur (3IM), imeps
     (3IM), imgif (3IM), imhdf (3IM), imico (3IM), imicon  (3IM),
     imiff  (3IM),  immpnt (3IM), impbm (3IM), impcx (3IM), impgm
     (3IM), impic (3IM), impict (3IM), impix (3IM), impnm  (3IM),
     imppm  (3IM),  imps  (3IM),  imras (3IM), imrgb (3IM), imrla
     (3IM), imrle  (3IM),  imrpbm  (3IM),  imrpgm  (3IM),  imrpnm
     (3IM),  imrppm  (3IM),  imsynu  (3IM),  imtga  (3IM), imtiff
     (3IM), imviff (3IM), imx (3IM), imxbm (3IM), imxwd (3IM)

AUTHOR
     Chris Groening
     San Diego Supercomputer Center

     See the individual file format man pages for the authors  of
     the  underlying  format  read  and write code.  The names of
     these man pages begin with the letters "im," followed by the
     format  name.  For example, the name of the TIFF man page is
     imtiff.  To display it, enter man imtiff.

CONTACT
     SDSC consultants, (619)534-5100, consult@y1.sdsc.edu

































SDSC              Last change: October 13, 1992                 3



