User`s guide
INDEX
74
use the Input | Lock image color (p. 62) option.
Advanced Option: This option is displayed whenInput | Lock image color (p. 62) is set.
Color | White point (%)
The white point is used by the color balance algorithm and is computed by using the
histogram of each color in the image. Use this option to leave the white point at the
maximum intensity (0%), or to choose the white point such that some percentage of the
pixels in the image are above the white point.
The default white point is 1% (that is, the brightest 1% of pixels are all converted to pure
white). Setting a higher value will cause tones close to white to become pure white.
This can improve contrast and overall intensity of the image. Setting the white point
too high will cause details in areas of highlights (e.g. the gray puffs of a cloud) to be
lost, making the image look flat.
Advanced Option: This option is displayed when "Color | Color balance" is set
andInput | Lock image color (p. 62) isn't set.
Color | White point red/green/blue
This option lets you set the white point manually. Note that these values are in linear
space, not gamma corrected space, so the only practical way to use these values is to
use the Input | Lock image color (p. 62) option.
Advanced Option: This option is displayed whenInput | Lock image color (p. 62) is set.
Color | Threshold
Use this option to change the brightness of text or line art scans.
Basic Option: This option is displayed when scanning one bit per sample.
Color | Invert
Use this option to invert black and white when scanning text using white letters on a
black background.
Basic Option: This option is displayed when scanning one bit per sample.
Color | Curve low/high
Use these options to change the shape of the curve that's applied after the black/white
point is applied.
Decrease the low value to see more detail in the black parts of the image, and increase
the high value to see more detail in the white part.
You can set Prefs | Graph type (p. 95) to "Curve" to see the curve, and can move the
triangles under the curve to change these values.