Measuring Images
Mira provides many tools for measuring and quantifying images, including distance and angle, statistics, shape measurements, and others. The Extract Sources command from the MExtract Module performs automated detection and numerous measurements of both resolved and unresolved sources.
Measurement procedures are operated through buttons, menu commands, and Window 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 Window Toolbars all have a similar interface
Point Sampling: The "live" cursor in the image window measures image coordinates and values.
These commands also have menu commands in case the button is not accessible.
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.
Points: Reports multiple measurements of coordinate & point luminance.
Lines: Reports multiple measurements of distance or length and angle.
Angles: Reports multiple measurements of included angle and base angle.
Regions: Reports multiple measurements of polygon area, perimeter, and luminance.
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The difference between measurements made by the mouse pointer and image cursor is generally as follows:
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In addition, data displayed in a Plot Window have access to the 1-D Fit Package for doing regression analysis.
Coordinate Calibration
The Extract Sources command detects objects in an image and extracts their properties such as coordinates, ellipticity, luminance, etc. This command is available with the optional MExtract module. The extraction procedure runs without any interactive marking procedure except for marking a region of interest if not scanning the entire image.
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.
Report Windows, Window Toolbars, Image Windows, RGB Image Commands