SeaDAS Help - Applying Color Schemes and Palettes

The Color Manager tool displays and modifies the color scheme and color palette used in a visual image of a band's data.

Tools -> Color Manager
Docked: left-side

Schemes and Palettes

A color palette refers to a set of rgb color values with corresponding (preferably normalized) data values. A color scheme denotes which color palette to use, the minimum and maximum values to apply to the palette, and whether the palette is to be displayed with log or linear scaling.

The color palettes are stored in color palette definition (cpd) text files. New cpd files can be created within SeaDAS as well as saved.

The color schemes are stored in the following text files(located in ~/.seadas/beam-ui/auxdata/color-palettes) :

color_palette_schemes.txt : contains the schemes.
color_palette_scheme_defaults.txt : a lookup table to set the scheme based on the band name
color_palette_scheme_selector.txt: a lookup table to set the scheme in the scheme selector in the GUI

Note: All color schemes and cpd files are located in the .seadas directory (~/.seadas/beam-ui/auxdata/color-palettes/). External cpd files can be copied into this directory and will show up in SeaDAS when it is next launched. Scheme files can be hand-edited to add new schemes or modify existing ones.

Editors

The color manager contains 3 editor screens:

Basic Editor:
- load scheme
- load/save cpd file
- set range minimum maximum
- set scaling: log/linear
- reverse direction of color palette
Sliders Editor:
- displays histogram on top of color-bar
- automatically or manually adjust individual value-color point pairs using movable sliders
- add/remove value-color point pairs
- generate statistics for minimum and maximum band data value
Table Editor:
- change value-color point pairs using a text field table

Basic Editor

Icons

: resets to the default color scheme
: toggles between log and linear display, redistributing palette points accordingly

Scheme Panel

Standard Schemes Selector : Select and load a pre-defined scheme. The loaded scheme name will be displayed directly above this selector. Any alteration to parameters subsequent to selection of a scheme will result in an asterisks displayed with the scheme name.

Note: this selector selects schemes from the 'color_palette_scheme_selector.txt' file, if the scheme was loaded by default then the scheme name comes from 'color_palette_scheme_defaults.txt' file.

Cdp File Panel

Color Palette Selector : Select a cpd file. Selector shows a visual representation of each color palette as a color bar. Hovering the mouse over a selection will display it's cpd file name.
Load cpd file exact values : selecting this checkbox will load in the cpd file values exactly as they are, replacing the currently loaded Minimum and Maximum range values as well as the log scaling with those of the cpd file. Unchecked, the behavior is to load in the palette, while maintaining the user selected log scaling, and redistribute the palette data points between the user currently selected Minimum and Maximum range values.
Save CPD File Button : save the current settings to a new cpd file name. Once saved, this new cpd file becomes the currently selected cpd file in the Schemes Panel. Additional save format options are CPT and PAL.
Reverse Button : reverses the direction of the color palette

Range Panel

Min Textfield : redistributes the palette using this minimum range value
Max Textfield : redistributes the palette using this maximum range value
Set from Band Data Button : redistributes the palette using band data statistics to determine the minimum and maximum range value.

Sliders Editor

Sliders

Change Data Value : left clicking a slider and moving it will alters it data value for that value-color point pair.
Change Color : left clicking a slider brings about a color dialog box to enable an alteration of the color for that value-color point pair.
Add Value-Color Point Pair : right click a slider to add a new point AFTER the slider clicked
Remove Value-Color Point Pair : right click a slider to remove that slider's value-color point pair

Rough Statistics : this underlined selected option will appear in the information above the histogram display if the current statistics are rough statistics. Clicking on this will enable the running a complete band statistics which includes all pixel data value in the determination of the data minimum and maximum range.

Icons

: resets to the default color scheme
: toggles between log and linear display, redistributing palette points accordingly
: adjusts the sliders to cover 95% of all pixels in the band.
: adjusts the sliders to cover 100% of all pixels in the band.
: zoom in on the histogram display vertically
: zoom out on the histogram display vertically
: zoom in on the histogram display horizontally
: zoom out on the histogram display horizontally
: distributes the sliders evenly between the first and the last slider.
: toggles visibility of statistic information in histogram display

Table Editor

For each value-color point pair the color and/or it's value can be changed with this editor.

Icons

: resets to the default color scheme
: toggles between log and linear display, redistributing palette points accordingly

More Options

No-data color : selects no-data color for this band
Histogram matching : It is sometimes desirable to transform an image so that it's histogram matches that of a specified functional form. It is possible to apply an equalized or normalized histogram matching to images which can often improve image quality.
Discrete colors : use only the discrete colors as defined in the palette

Preferences

The following preferences GUI governs this Tool

Currently the only option is whether to use the color-blind compliant palette as the default palette. (see color_palette_schemes.txt located in ~/.seadas/beam-ui/auxdata/color-palettes)

RGB Image

*Note: this section of the help page is slightly out of date - see SeaDAS 7.4 Release Notes

Images using separate R,G,B channels use obtain their colours from the samples of three arbitrary bands. In the editor, users can switch between the channels in order to edit the contrast stretch range and gamma value of each channel separately.

In this mode the sliders are used for contrast stretching in each of the R,G,B channels. In the More Options panels, you can adjust the No-Data Colour and Histogram Matching for the final image. The Source Band and Gamma options apply to each channel. The gamma value is used to adapt the transfer function which quantises the band's sample values to colour values. A gamma value of 0.7 for the blue channel enhances most RGB images.