Plotting Region Histograms
Use the Histogram tool to plot the intensity distribution within a region on any dataset available in the Data Properties and Settings panel. Histograms, which show the number of pixels found at each different intensity value(s), have many uses. One of the most common is to help determine a threshold value to use for post-processing. For example, if an image is suitable for thresholding then its histogram will be bi-modal and pixel intensities will be clustered around two well-separated values. A suitable threshold for separating these two groups will be found somewhere in between the two peaks in the histogram.
Region histogram
For an 8-bit grayscale image there are 256 different possible intensities. The histogram will graphically display the distribution of those grayscale values within a specific number of bins.
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Tools |
Allows you to pan, zoom, and reset the histogram (see Using the Histogram Tools).
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Y log |
If selected, the Y-axis will be plotted in log scale. |
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Dataset |
Indicates the image data from which the values are plotted and provides a drop-down list for selecting other datasets. |
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Statistics* |
Describes the plotted values as follows: Minimum… Indicates the minimum value within the region. Maximum… Indicates the maximum value within the region. Mean… Indicates the mean value within the region. Standard deviation… Indicates the standard deviation of plotted values. |
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Export to CSV |
Lets you export histogram data in the CSV file format. |
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Copy to Clipboard |
Copies the histogram statistics to the clipboard. |
* Values are calculated for the selected image data and expressed in the native units of the dataset.
How to Plot a Histogram
- Select the required region in the Data Properties and Settings panel.
- Click the Histogram button in the Tools box in the bottom section of the panel.
The histogram of the selected region appears.
- Select another dataset in the Dataset drop-down menu to plot its values in the histogram, if required.
Using the Histogram Tools
The Histogram tools allow you to pan and zoom, as well as reset the histogram.
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Icon | Description |
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Pan |
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Lets yo pan the figure, as follows:
NOTE You can also click with the right mouse button and then drag left and right to Zoom in and Zoom out on the X axis. |
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Zoom |
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Lets you zoom in or zoom out, as follows:
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Reset |
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Resets the original view of the figure. |
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Save |
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Lets you save the figure as a bitmap image, vector graphic, or in the PDF file format. Figures can also be saved as raw data or PGF code for LaTeX. |
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Settings |
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Lets you edit the captions on the histogram, apply scaling, and set a data range. These options are available in the Figure options dialog, shown below.
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