Measuring Images

Mira provides a rich assortment of tools for measuring and quantifying images, including distance and angle, area statistics, statistics, photometry, shape measurements, and others.

Measurement procedures are operated through 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 displayed in a Grid Control (also called a "report" or "table") You can also create a scatter plot (see the Create Plot from Grid command), including error bars, from two columns in a table of measurements. Other types of plots and point samples are also useful for quantifying images. See Plotting Image and Data and Image Coordinate Readout).

Measurements are divided into classes according to 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. Most of these measurement packages have counterparts in the Pro Script module. See the Mira Pro x64 Script User's Guide for details.

Measuring a Single Image or Image Set

Most measurements offer the option to measure one or all of the images of an Image Set. If an Image Set is open in the Image Window, you can choose whether to measure only the currently displayed member of the image set or to repeat the measurement for all images of the image set. This is done using theMeasure Image Set button in the Image Set Flags group on the Image Bar. When the button face shows a "1", then only the current (one) image is measured, otherwise, the entire image set is measured.

Image Cursor Measurements

These measurement package work from a toolbar but use the Image Cursor to mark the point or region to be measured. They list their results in a Report Window or a Measurement Pane. These commands can also be operated using a single keystroke commands in the Image Window. See the Image Keys Pane.

• Centroid : Reports a high precision position for a peak or trough.

• Statistics : Reports statistics inside a rectangular region. Use the Statistics Properties to select the statistical estimator and set its parameters.

• FWHM : Reports the Full Width at Half Maximum value for a peak.

To change the destination of the measurement, go to the Cursor Tools Toolbar and select the output target using the drop-menu next to the command icon.

Toolbar Measurements

These measurement packages operate from toolbar and use the mouse pointer rather than the image cursor. The results are listed in a Report Window or Measurement Pane.

• Distance & Angle: Measures the distance and angle between two points.

• Angle Measurements: Reports measurements of included angle and base angle.

• Line Measurements: Reports measurements of distance or length and angle.

• Point Measurements: Measures point coordinates and pixel intensities.

• Region Measurements: Reports measurements of polygon area, perimeter, and luminance.

• Aperture Photometry: Makes photometric measurements of stars and other objects.

• Star Removal: Subtracts stars from images by building and applying a template for the star profile.

• Plot Line Measurements: Reports the distance between points on a plot.

• Plot Point Measurements: Reports the coordinates of points marked on a plot.

• Statistics Measurements: Reports the statistics of an image region or of a plot series.

Measurements without a Toolbar

Image Coordinate Readout: The "live" cursor in the image window measures image coordinates and values.

Plot Coordinate Readout: The Plot Bar reports the "live" x,y coordinates of the plot window cursor.

Source Extraction

The Extract Sources command detects sources in an image and extracts their properties, including coordinates, ellipticity, intensity, orientation, and more. The extraction procedure runs without any interactive marking procedure except when finding sources within the rectangular bounds of the image cursor. Source extraction can also be scripted using the CImExtract class in the Pro Script module. See the Mira Pro x64 Script User's Guide for details.

Measuring RGB Images

Making measurements of intensity images is straightforward. However, RGB color images contain a separate image of intensity 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:

1. Use the Extract Channel command to separate the color channels. If extracting more than 1 channel, check theCreate Image Set option so that all extracted images end up in the same Image Window.

2. If you extracted more than 1 channel, press on the new window so the entire Image set will be measured.

3. Perform the measurement on the extracted channels. The result for each channel is reported in the same way as for an intensity image.

Related Topics

Contents

Grid Controls

Measurement Panes

Report Windows

Command Toolbars

Image Windows

Working with RGB Images

Create Plot from Grid

Create Chart from Grid

Extract Sources command

Open Table in Excel

Image Keys Pane

Mira Pro x64 User's Guide, Copyright Ⓒ 2023 Mirametrics, Inc. All Rights Reserved.