Colormap Editor

The Colormap Editor is used to carry out a very wide range of color fiddling and editing. Colormaps are remembered by aipsview as ``palettes''; these palettes may be saved to files for reloading later.

**Figure 3.2:** **Colormap Editor** Window
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Shown just below the menu bar is the name of the current palette. When aipsview first starts up, the ``Clipboard'' palette (loaded with the Rainbow colormap) is used (n.b., the Clipboard's name is not changeable; however other palette names can be changed). You can either edit the colors in the Clipboard palette directly, or copy a predefined colormap (listed in the Palettes menu, see 3.3.1) into it.

The colormap editor also allows you to save palettes to files for reloading later. Unlike the Clipboard's name, user palette names loaded in from files may be edited in the Palette name field. After editing a palette's name, you need to press <RETURN> for it to take effect. Users should avoid giving multiple palettes the same name. If a user-supplied palette has the same name as a predefined palette, the user's palette won't be selectable. Palette names should not contain blanks or non-printable characters. Since the colormap editor does not check names when creating files, it is possible to create filenames with blanks. Names should be less than 32 characters in length.

Main Menu Bar

There are three menu buttons: File, Palettes, and Options.

File Menu

New: This creates a new palette entry with the current colors. An initial name will be provided which the user may edit.
Open...: This creates a new palette entry with the contents of the file. The file's name will be used as the palette name. If a palette already exists with that name, it will be reused.
Save: The current palette is saved using the palette's name as the filename.
Save As...: The current palette is saved to a file for later retrieval. You will be prompted to supply a filename.
Delete: The current palette is deleted. The Clipboard will become the current palette. The Clipboard cannot be deleted.
Close: Exits the colormap editor.

Palettes Menu

The first entries are predefined colormaps. When selected, their values are copied into the currently selected palette. Selections are the following:

Grayscale: Switch to the grayscale built-in palette. If RGB is the active color model, then sync the R,G,B graphs as if Gray item under the Options had been selected.
Rainbow: Switch to the rainbow palette. This palette is a linear hue ramp from purple to red at maximum saturation and value.
Logarithmic: Switch to a logarithmic (rather than linear) mapping between data intensity values and palette display values.
Pseudo-Contour: Use a single color to display a pseudo contour representation of the data.
Multiple Ps-Contour: Use four colors to display four pseudo contours.

Below the predefined colormaps are two copy operations that may be used to copy the contents of one palette to another:

Copy to Clipboard: Copy the colors of current palette to the Clipboard.
Copy from Clipboard: Copy the contents of the Clipboard to the current palette.
Clipboard: This (and all name below Clipboard if a personal palette has been chosen) is the name of a palettes that can be manipulated. Clipboard is the default palette that specific palettes can be copied to and from. Note that this palette cannot be deleted.

Entries below the line are added and deleted by File menu operations. When one of these is chosen, it becomes the current palette and may be edited. There is a limit of 32 user-supplied palettes.

Options Menu

Gray: Switch to RGB (red, green, blue) mode and synchronize the graphs such that only grayscale values are generated.
RGB: Switch to RGB mode and unsync the graphs; this is the default.
HSV: Switch to HSV (hue, saturation, value) mode. When switching between RGB and HSV, the graph values are converted to show the same palette.
Show Alpha: Toggle to turn on/off the alpha graph, (n.b., alpha is the transparency of a volume rendered image, not currently implemented in aipsview).
Reset Map: Reset the palette to the default values.
Auto Update: Automatically redraw the image in response to changes in the colormap. This button only appears when displaying on a TrueColor window. By default the image is redrawn when the mouse button in the colormap editor is released (although the color bar in the editor continuously changes). When Auto Update is selected, the image is redrawn in continuously; note that when displaying large images or running on slow machines, the auto update mode may be unacceptably slow. See Section A.4 for more information on TrueColor display.

Colormap Display

Just below the menu buttons is a display of the palette or color look-up table that is in use. If all colors are not used by aipsview, the left and right parts of this display will be blank, representing the missing colors. You may interactively adjust the zero point and contrast of the palette by placing the mouse pointer within this display and moving the mouse both horizontally (zero point) and vertically (contrast) while holding down the left mouse button.

**Figure 3.3:** **Colormap Editor** Look-up Table
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The graphs shown represent the RGB (or HSV) color values across the range of colors made available to aipsview when it was first loaded.

The letter in the upper left corner of each graph describes which component of the colormap it controls (R for Red, G for Green, B for Blue, H for hue, S for saturation, V for value, and A for alpha). Note that alpha is not currently implemented in aipsview). The editor as a whole may operate not only in RGB mode, but also may be changed to operate in RGBA, HSV, and HSVA modes with the Options menu.

Editing the Colormap

At the top of each graph are a series of buttons which are used to select the kind of function to create. The functions available are, from left to right, Draw (freehand draw the graph with the mouse), Constant, Linear, Log/Exponential, Piece-wise Constant (or Stairstep), Piece-wise Linear, Spline, and Repeat.

**Figure 3.4:** **Colormap Editor** Editing Graph
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Draw: Move the cursor to the graph and press the mouse button on the graph to sketch the graph manually.
Constant: A single control point (a solid square with the default color yellow) sets the value for the function.
Linear: Two control points are provided which may be moved anywhere on the graph. A linear function is fit between the points.
Log/Exponential: Three control points are provided. An exponential curve is fit to the three points.
Piece-wise Constant (or Stairstep): Constant function between each point.
Piece-wise Linear: Linear function between each point.
Spline: A spline curve is fit to the points. The spline curve of two variables is not normally a proper function, so some degeneracies may occur during this mode.
Repeat: The Repeat function can be applied to all above modes except Draw and Constant. It is used to repeat a function between the first and last control points to the rest of the graph. For example, a sawtooth function is created by repeating the linear function. More complex repeating functions are possible by applying Repeat with other modes.

In all modes expect Draw, control points are moved by ``grabbing'' them with the mouse and dragging them to a new place. Control points can be added to the Stairstep, Piece-wise Linear, or Spline modes by pressing the left mouse button far enough (five pixels or so) away from any existing control points. In these modes, control points are deleted when they have the same X value. Simply put, the control point being moved absorbs any others within its horizontal motion.

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