gimp/plug-ins/print/README

Print plugin for the Gimp.  Version 3.0.6 by Robert Krawitz
<rlk@alum.mit.edu> based on version 2.0 by Michael Sweet
<mike@easysw.com>.

This version has numerous enhancements:

1) Full support for the Epson Stylus Photo, Photo 700, and Photo EX
   printers, including 6-color printing, 1440x720 dpi resolution, and
   "soft" weave for much faster high quality printing.

2) Many new controls, including:

   * Output gamma adjustment
   * Contrast
   * Red/green/blue levels
   * Saturation
   * Density
   * Additional scaling options

3) Improved tonal resolution.  Calculations are now done in 16 bit
   rather than 8 bit resolution, which eliminates stair stepping.
   Input levels do not map one to one onto output levels, so in 8 bit
   output resolution multiple input levels will map to a single output
   level.  Usually the density range is compressed in the light end of
   the tonal range, so many different input levels will map to one
   output level.  Use of 16 bit output resolution avoids this
   undesirable behavior and results in smooth tonal gradations in
   highlights.

4) Saving of all settings between print jobs.


This plugin has been optimized for the Epson Stylus Photo EX, since
that's the printer I own.  I am interested in comments on performance
both with Epson Stylus printers and with others.

Some tips on tuning the output:

* Start with the default settings

* Brightness and density are not the same thing.  Density is a purely
  linear adjustment; more density means more ink.  Brightness affects
  perceived brightness.

* Higher gamma values result in brighter images with compressed
  highlights.  Lower gamma values are darker, but with better tonal
  range in the highlights.

* Different brands of ink yield different results.  I've found that
  third party inks on Epson printers are generally too cyan.  The
  correction for excessive cyan is to add red (or reduce blue and
  green).

* I've found that what creates good test patterns does not necessarily
  create good photographs.  In particular, test patterns often print
  well with gamma of .6 or thereabouts, but that gives washed out
  photographs.  Perhaps when I implement a better contrast control
  this can be improved.

* The contrast control scales polynomially around the midpoint of the
  range.  Lower contrast will reduce the contrast in the midtones, but
  increase the contrast in the highlights and shadows.  Contrariwise,
  a high contrast value will stretch the scale in midtones,
  compressing the highlights and shadows.

* There are many combinations of brightness, gamma, and density that
  will create acceptable images.  You may find that you want different
  settings for different images.

* One group of settings you might want to start with is:

  Brightness 45
  Gamma 1.5
  Contrast 105
  Saturation 1.4
  Density 0.8


Makefile.standalone enables you to build this plugin as a standalone
plugin, without reference to a Gimp source tree.


Enjoy!

-Robert Krawitz, January 13, 2000