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A-61122/A-61124 March 1999 E-15
ATP Threshold settings
The threshold parameter controls the lightness and darkness of
the background in an image. Threshold can have a value
between 0 and 255, with a default value of 90. As the threshold is
increased, more of the darker grays in the image will become
black. As the threshold is decreased, fewer of the darker grays
will turn black.
Image C was processed with default settings, and threshold set to
60. Image D was processed with the threshold set to 110. Notice
that blocks 8, 9, 10 and 11 have a black background in image D
and a white background in image C. Since image D has a higher
threshold than image C, and the background grays in blocks 8, 9,
10 and 11 are not above the threshold 110, the pixels are black.
In image C, the background grays in the same blocks are above
the threshold of 60, so these pixels are white.
Image C
Image D
NOTES:
• Threshold and contrast work independently and have no
effect on each other.
• When using the ATP accessory, mixed mode/error diffusion
and screening are not available. When using the ATP
accessory, the results, when using the Image Enhancement
or Noise filter, may vary from the results obtained with
standard image processing.