PLEASE NOTE :   This is the documentation for the avs module executable
output_dither, which contains the following modules:

	vdith45
	vdither
	verrdif

Any mention of xvimage is actually a "field 2D".  Also, the INPUTs and
OUTPUTs, which are mapped to avs parameters, inputs, and outputs, are for the
khoros library routine.
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Documentation for avs module vdith45


INPUT
     image          xvimage structure  containing  the  character
                    image to be dithered.

OUTPUT
     image          holds the result of the dithered image.


DESCRIPTION
     vdith45 performs an 8x8 ordered  block  dither  with  major
     axes  lying  along the 45 degree diagonals. This dither pro-
     vides lots of grey levels at the expense of spatial  resolu-
     tion, and is relatively easy on the eyes from a distance.
     image is a pointer to a Khoros  image  structure  containing
     the  character  image to be dithered.  image is also used to
     hold the result of the dithered image.  This is done to save
     space,  but  you  must be careful not to overwrite important
     data.

     vdith45 returns a value of one upon success and a  zero  on
     failure.

SEE ALSO
     vdith45(1), intro(3), vipl(3), verror(3), vutils(3)


RESTRICTIONS
     vdith45 operates only on data storage type BYTE images.

AUTHOR
     Scott Wilson


COPYRIGHT
     Copyright  1991,  University  of  New  Mexico.   All  rights
     reserved.

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Documentation for avs module vdither


INPUT
     image          xvimage structure  containing  the  character
                    image to be dithered.

     type           an integer flag indicating the type of  dith-
                    ering (matrix) technique desired.

OUTPUT
     image          holds the result of the dithered image.

     Return Value:  1 on success, 0 on failure.


DESCRIPTION
     vdither performs 5x5 ordered dithers.  These dithers provide
     a  reasonable  compromise  between  grey  levels and spatial
     resolution.

     image is a pointer to a Khoros  image  structure  containing
     the  character  image to be dithered.  image is also used to
     hold the result of the dithered image.  This is done to save
     space,  but  you  must be careful not to overwrite important
     data.

     type is an integer flag used  for  indicating  the  type  of
     dithering  (matrix)  technique  desired.   The  two types of
     matrices supported are Star (1) and Box (2).

     vdither returns a value of one upon success and a  zero  on
     failure.

SEE ALSO
     vdither(1), intro(3), vipl(3), verror(3), vutils(3)


RESTRICTIONS
     vdither operates only on BYTE images.


AUTHOR
     Scott Wilson


COPYRIGHT
     Copyright  1991,  University  of  New  Mexico.   All  rights
     reserved.

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Documentation for avs module verrdif


INPUT
     image          xvimage structure of the character  image  to
                    be dithered by error diffusion.

OUTPUT
     image          holds the result of the dithered image.

     Return Value:  1 on success, 0 on failure.


DESCRIPTION
     verrdif performs a dithering operation using four-direction
     error  diffusion.  This dither produces images that are easy
     on the eyes up close.  They also have  good  greyscale  from
     far  away,  except  when the image has slowly varying inten-
     sity.  In that case,  some  peculiar  patterns  may  appear.
     image  is  a  pointer to a Khoros image structure containing
     the character image to be dithered.  image is also  used  to
     hold the result of the dithered image.  This is done to save
     space, but you must be careful not  to  overwrite  important
     data.

     verrdif returns a value of one upon success and a  zero  on
     failure.

SEE ALSO
     verrdif(1), intro(3), vipl(3), verror(3), vutils(3)


RESTRICTIONS
     verrdif operates only on BYTE data storage type images.

AUTHOR
     Scott Wilson


COPYRIGHT
     Copyright  1991,  University  of  New  Mexico.   All  rights
     reserved.

*********************************************************************************