# gamma and xscanimage

From: mh (crapsite@gmx.net)
Date: Tue Nov 07 2000 - 02:08:37 PST

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  Hi,
  at the moment I'm trying to implement gamma-table options in the pnm backend
  (I need this for some tests).
  I did the following:

  { /* grayscale gamma vector */
  "gamma-table",
  "Image intensity",
  "Gamma-correction table. In color mode this option equally affects the " \
  "red, green, and blue channels simultaneously (i.e., it is an intensity " \
  "gamma table).",
  SANE_TYPE_INT,
  SANE_UNIT_NONE,
  sizeof(SANE_Word)*256,
  SANE_CAP_SOFT_SELECT | SANE_CAP_SOFT_DETECT | SANE_CAP_INACTIVE,
  SANE_CONSTRAINT_RANGE,
  {(SANE_String_Const *) &gamma_range}
  }

  and the same for red, green and blue.

  I initialize the gamma tables like this:

  for(i=0;i<256;i++)
  {
  gamma[0][i] = i;
  gamma[1][i] = i;
  gamma[2][i] = i;
  gamma[3][i] = i;
  }

  Now I expected to see a line in the gamma widget in xscanimage from left/bottom
  to top/right. However, the line is drawn for 25 percent of the widget, the rest
  displays garbage.
  (please see: http://users.yoobay.org/crapsite/etc/gamma.png)
  Is this a known problem with xscanimage or must the gamma options have
  a size of 1024*sizeof(SANE_Word)?

  Thanks
  Michael

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