ProRaster Help – Color Table Editor

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Using the Color Table Editor dialog

Color tables are used exclusively in the LUT Color layer as the source of color for the Color component. Opacity components use a fixed table, as do the Red, Green, and Blue components in an RGB Color layer. To select a color table for use in a LUT Color layer, you must first make that table available to ProRaster using the Color Table Editor dialog.

 The Color Table Editor manages the color table resources that ProRaster can access. It provides a preview of all color tables under management, allows you to connect new tables that exist in external directories, create new tables, copy existing tables, and provides tools to edit color tables, maps, and legends.

 There are four different kinds of color tables – ramps, tables, maps, and legends. A color table ramp is a programmatically defined color table. The first and last color are defined, and all the intervening colors are created by interpolation in either RGB or HSL space. A color table is a file on disk and, even though it can be in a variety of different formats, ProRaster will only write color tables in one format – the XLUT format. The colors in the table may all be defined individually, or they may be created by interpolation when loaded. A color table map is a color table on file that includes a data map, generally listing a data value associated with every color value. Multiple formats are supported for reading, but maps are only ever written in XLUT format. A color table legend is a list of data values, ranges, or strings along with rendering information including color. ProRaster supports the LEG format for reading and writing legends.

Category list

The editor lists all the color tables managed by the system by category. Select a category, and a list of all the color tables therein will be displayed. The icon for each table reflects whether it is a ramp, on disk, contains a data map, or a legend. Select a color table in the list and a preview will be rendered at the base of the dialog. The category list contains the following categories:

Local Algorithm Color Tables: These are color tables that have been loaded from the current MRD algorithm that have not been matched with any known color table under management.

Recently Selected Color Tables: This is a list of color tables that you have recently used and duplicates color tables from other categories.

System Color Ramps: A color ramp is a simple table that interpolates between two defined colors. These are programmatically created and are not stored in any file.

System Color Tables: The color tables that were shipped with ProRaster and are stored in the C:\ProgramData\RGE\ColorTables\SystemTables directory.

System Color Maps: The color table maps that were shipped with ProRaster and are stored in the C:\ProgramData\RGE\ColorTables\SystemMaps directory.

User Defined Color Tables: Color tables, color table maps, and color table legends that have been created by you and saved into the default directory at C:\ProgramData\RGE\ColorTables\UserTables.

External Folder […]: An external directory that contains color table files that you have linked to ProRaster. You can link multiple external folders.

 In the editor, a button is provided to “Add a new external directory”. If you have color tables files in a directory that you have created, or you have color tables in files in a directory installed by another software package, then you can link this to ProRaster and, thereafter, any color tables that ProRaster can read will be available for use in your algorithms. A second button is provided to “Remove the selected external directory” so that ProRaster forgets about its contents.

 The ”Clear recently accessed list” button simply erases the list of recently selected color tables. This does not actually remove any color tables.

 The “Delete the selected color table” button allows you to delete files from external folders or from the user-defined color tables directory. Care should be taken. The files will not be deleted until you hit “OK”.

Creating color tables

If you have the “user defined color tables” category selected, or any external folder category selected, then you can hit the button to “Create a new color table for a classified raster”. This option is designed to generate color table legends for classified and image palette fields for a selected raster source. When rendering classified data, you can use a LUT Color layer and color transform and modulate by the legend produced by this option. Furthermore, you can edit the legend and remove items to prevent certain classes being rendered.

 Hit the “Create a new color table for a classified raster” button. A dialog is presented showing the output file path and name. As always, you must specify a unique name for the color table. Then choose a raster source from the list and choose a classified or image palette field from that raster source. Hit OK and the new color table legend, using discrete value matching, will be created.

 Two more creation options are provided – to “Create a new color table in the selected folder” and to “Create a new color table from the selected table”. The first option will create a new table in the user defined or external directory. The second option will create a new table in the user defined directory by copying at least some elements of another table. Both options will then open the “Create Color Table” dialog.

 The dialog will show you where the color table will be written. Your first task is to choose a unique name for the table which will double as a filename. The dialog will indicate to you whether the name you have selected is unique.

 Secondly, you need to specify what kind of table it will be – a Table, Map or Legend. If you choose Legend, then you need to specify the number of items in the legend and whether the legend will use data values, data ranges, continuous data ranges, or data text strings.

 If you are copying a color table, then the colors and data in that table will be used to populate the new table as applicable, regardless of what type the new color table will be. Hit OK to create the table and you will be returned to the main dialog. Your new color table will be visible in the list of color tables. You can double click on the table in the list to edit it or select the table and hit the “Edit” button.

Editing color tables

The editor dialog contains a preview of the color table at the top and a spreadsheet of the data. An “Undo” button is provided to undo changes. The total number of colors in the table is reported under the color preview. For a standard color table, you can also change the interpolation method between RGB and HSL color space. In the spreadsheet, you can duplicate the current row by navigating to the rightmost cell of that row and hitting the return key (the row will be duplicated below). You can delete the previous row by navigating to the leftmost cell of a row and hitting the delete key (the row above will be deleted). You can also delete a row by clicking on the row header cell and hitting the Delete key.

You can build a color table or map by defining every color as a row in the sheet, or you can define a set of key colors and allow the colors in between to be generated by interpolation.

To specify a color, click on the color cell in the sheet. Select one of the pre-defined colors or hit the “Custom” button to open a more advanced color selection dialog. Note that you only need to specify the RGB components of the color. The alpha component is not used. Whenever you make any change to the table, the preview graphic is updated to reflect the change.

The row index tells you zero based color index of the color in that row. The “Count” column is the number of colors defined by the row. The colors for the row will be found by interpolation from the row color and the next row color. The count value should be one or more, and the count value for the last row ought to be one.

 A color table map has an additional “Data” column which allows you to associate data values with colors in the table. The data values must be monotonically increasing, and you should always define a data value for the top and bottom colors. It is not necessary to define a data value for each key color in the table, but it is likely that you will. To use a table like this in an algorithm, select it as both the data transform and the color table.

A color table legend is a more traditional arrangement where each row in the spreadsheet contains a color and a data value or range of data values, and the table consists of only so many colors as there are rows in the table. No color interpolation is used.

Legends that contain a data value or text string per row are generally used to colorise integer data, such as is commonly found in classified rasters. Data values in the raster that do not match any value in the legend may not be rendered.

Legends that contain a data value range can be used to colorise continuous data. Ranges can be discrete or continuous. In the first case, any data that is >= the minimum and <= the maximum is considered in the range. In the second case, any data that is >= the minimum and < the maximum is considered in the range. The “Continuous range” legend is designed for ranges that touch each other but do not overlap. In either case, any data that is not inside a range will not be rendered.