Image Palettes
An image palette is a color mapping between image
brightness and some number of colors. Mira uses 256 palette entries
per channel to display an intensity image (i.e., an image not in
RGB format). For such images, the image levels are set by the
Transfer Function, then a palette of colors is
assigned to each level of the transfer function. Since there are a
discrete number of levels in the transfer function that must cover
some range of image intensity, there is a range of intensity
assigned to each palette color. By changing the color assignment to
the palette indices, you can change the way the image is
rendered.
Selecting a Different Palette
The
Palette Properties dialog provides access to
different palettes other than the default grayscale palette. Use
the selection box in the
Palette Properties dialog to choose a different
palette. You can adjust a palette without saving the changes using
controls in the
Palette Properties and in the
Palette Pane. The
Import Palette and
Export Palette commands in the View > Palette menu are used to move palettes
between Mira and Palette files (such as the
collection of palettes in thePalettes
folder (see
Mira's Special Folders).
To permanently save changes to a palette, use the
button to open the palette profile
menu. The fundamental palettes such as grayscale are protected
against change and cannot be overwritten. However, addition
palettes you import can be overwritten with changes. The palette
profile menu has two different forms as shown below.
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Fundamental Palette: overwriting and
deleting are disabled.
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Imported Palette: Overwriting and Deleting
are enabled.
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Importing and Exporting Palettes
Importing
Mira is installed with a few fundamental palettes
including "grayscale", "random". and "level slice". These basic
palettes are stored in binary form in the Windows Registry. Mira
only loads palettes from the Registry. A rich collection of
pseudocolor palettes is provided in thePalettes sub folder of the Sample Images folder (see
Mira's Special Folders). These additional
palettes may be imported from files to the Registry using the
Import Palette command.
Exporting
Any palette currently displayed in an
Image Window can be exported from the Windows
Registry to a file using the
Export Palette command.
Changing the Image Palette
Images are converted from pixel values to the
screen display using two protocols: a Transfer Function for
non-RGB images, and a Palette for all images. The transfer
function converts image brightness values into a look-up table with
255 entries (255 per channel for RGB images). The palette then
assigns a color or shade of gray to each entry in the lookup table.
You can change both of these quantities from the Image Window:
Procedures for Changing the Image Palette
Contrast & Brightness
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Be sure the
Palette Pane is open, Then do the
following:
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Move the mouse cursor into the Color Map area.
You will see it change to a mode cursor with a yin/yang shape upon
entry.
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Mouse down to activate stretch mode, then drag
the cursor left/right to change brightness or up/down to change
contrast.
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Release the mouse button when finished.
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Gamma & Brightness
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Be sure the
Palette Pane is open, Then do the
following:
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Move the mouse cursor into the Color Map area.
You will see it change to a mode cursor with a yin/yang shape upon
entry.
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Mouse down to activate stretch mode, then drag
the cursor left/right to change brightness or up/down to change
contrast.
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Release the mouse button when finished.
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Related Topics
Contents
Palette Pane
Palette Properties
Transfer Functions
Image Windows
Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All
Rights Reserved.
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