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Adjust Color
The Adjust Color button button pops up a non-modal dialog that allows adjustment of various parameters related to the print quality. These are independent of the controls within the
GIMP itself and only affect the print.
At the top of the window is a thumbnail of the image that changes to reflect the color settings of the image. This enables you to get an idea of how the image will print out as you adjust settings.
Below that there are eight sliders:
- Brightness (0-2.0, default 1.0)
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adjust the brightness of the image.
- Contrast (0-4.0, default 1.0)
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adjust the output contrast.
- Cyan, Magenta, Yellow (0-4.0, default 1.0)
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adjust the cyan, magenta, and yellow in the output. These should not normally need to be adjusted very much; even very small adjustments can go quite a long way to restoring color balance..
- Saturation (0-9.0, default 1.0)
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adjust the color brilliance (saturation) of the output. Saturation of 0 means pure gray scale, with no color. Saturation of 9.0 will make just about anything but pure grays brilliantly colored.
- Density (0.1-2.0, default 1.0)
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adjust the density (amount of ink) in the print. The density is automatically corrected for the particular printer, resolution, and in some cases paper choices. If solid black in the input is not solid in the print, the density needs to be increased; if there is excessive ink bleed-through and muddy dark colors, the density should be decreased.
> **Note:** that the density will not increase beyond a certain amount no matter what the slider is set to.
- Gamma (0.1-4.0, default 1.0)
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adjust the output gamma. The gamma value is automatically corrected for the choice of printer; this is used if you believe the automatic setting is incorrect.
- Dither Algorithm
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There is also a selection box for the dither algorithm to be used. There are currently seven choices:
* Adaptive Hybrid usually yields the best output quality; it chooses a modified Floyd-Steinberg error diffusion algorithm or ordered dithering depending upon the image characteristics.
* Ordered uses a pure ordered dither. It generally yields excellent quality for simple black and white or four color printers without variable drop size or drop modulation; it is not recommended if high quality is desired on six color printers. It is considerably faster than Adaptive Hybrid.
* Fast also uses a pure ordered dither, but uses a very simple black model and makes no attempt to handle multi-level (6-color, variable drop size, or drop modulation) at all cleanly. It is substantially faster than Ordered dither. The quality tends to be quite poor except on simple four color printers. On three color printers, quality is probably competitive with anything else.
* Very Fast is similar to Fast, except that it uses a very simple dither matrix that can be looked up much more quickly than the matrix used in the Fast dither. For simple pure black and white images dominated by horizontal and vertical lines, this may actually yield the best results; for other types of image, the quality will be poor.
* Adaptive Random is similar to Adaptive Hybrid, except that the modifications to the Floyd-Steinberg algorithm are slightly different. This is slower than Adaptive Hybrid on most systems. For some images the quality may be better than Adaptive Hybrid, but generally Adaptive Hybrid should yield slightly superior images.
* Hybrid Floyd-Steinberg uses the modified Floyd-Steinberg algorithm of Adaptive Hybrid on the entire image. Generally, the results are poor in pale regions.
* Random Floyd-Steinberg uses the modified Floyd-Steinberg algorithm of Adaptive Random on the entire image. Generally, the results are poor in pale regions.