Igor grey-scale question

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Wed, 07/31/2013 - 11:51 am

What is the numeric range Igor uses to assign grayscale values? An example guess would be black = 0, white = 255, corresponding to the dynamic range of V_min and V_max in a given 2D image..

Just curious, because simply displaying an image often gives a great visual contrast, but getting a similar "contrast" (separation of proximal structures) using image thresholding is often very challenging, and it seems like the automatic grey-scale algorithm would be a good place to start.
You can use the ColorTab2Wave operation to explore the built in color tables. The help info for this operations states that the values in the color tables range from 0 to 65535 (16 bit integer values).

If you like the contrast automatically imposed by Igor, open the Modify Image Appearance dialog from the Graph menu for the current image. You will find the first and last values of the image that the color table ranges over. The first and last values can be changed to alter the contrast. You may aware of this already , but I mention it because it seems to fall into the question that you pose.

August 1, 2013 at 05:17 am - Permalink