Measuring Images
Mira provides many tools for measuring and quantifying images, including distance and angle, statistics, photometry, and others. These measurement procedures are operated through simple buttons, menu commands, and command toolbars. Measurements share a common user interface in terms of how the target object is marked and how the results are reported. Plots are another way of quantifying images. RGB color images have some special considerations, as described below.
Measurements are divided into two classes based upon whether they use the Image Cursor or the Mouse Pointer to mark locations. All measurements that use a toolbar use the mouse pointer. Conversely, all measurements that use the image cursor operate from a button (or a duplicate entry in a menu). All Command Toolbars all have a similar interface
These commands also have menu commands in case the button is not accessible.
Point Values: The image coordinate and value at any point are reported continuously by the mouse cursor.
Centroid: Reports a high precision position for a peak or trough.
Statistics: Reports statistics inside a rectangular region.
FWHM: Reports the Full Width at Half Maximum for a peak.
Distance & Angle: Reports the distance and angle between two points.
Aperture Photometry: Reports magnitudes in astronomical images.
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All measurements that use a command toolbar use the mouse pointer to mark or drag markers on the image. All measurements that use single command buttons use the Image Cursor as a position reference. |
Making measurements of luminance images is straightforward. However, RGB color images contain a separate image of luminance data for each of the 3 planes. When Mira measures an RGB image, it performs the calculations on an equivalent grayscale image and returns an equivalent measurement for a single "grayscale" channel. To measure any or all of the individual color channels in an RGB image, do the following:
Use the Extract Channel command to separate the color channels. If extracting more than 1 channel, check the Create Image Set option so that all extracted images end up in the same Image Window.
If you extracted more than 1 channel, press
on the new window so the entire
Image set will be measured.
Perform the measurement on the extracted channels. The result for each channel is reported in the same way as for a luminance image.
Contents, Report Windows, Calibrating Images, Command Toolbars, Image Windows, RGB Image Commands