This program, RadialPR.exe, is a highly specialized application for image processing associated with electron diffraction. Its main purpose is to automatically find the center of powder diffraction images taken under high noise conditions. We present it here mainly for demonstration purposes. Those who are curious are welcome to run the program but are unlikely to find it generally useful without additional changes.

        The images below show three stages of processing by RadialPR. The first shows the weak signal present in a 16-bit dynamic range 512x512 image obtained after an intense background image has been subtracted. The central circle and vertical bar are the shadows of supporting structures and this portion of the image will be ignored.

The second image is the radially symmetric component of the first image and the data of interest. The image intensity is increased from the first image for presentation. The third image is the asymmetric component and helpful for finding unexpected sources of noise.

        When the pixels in the second image are integrated over 360° about the image center we obtain the radial diffraction pattern shown on the image to the right. This pattern is representative of the molecule that caused the electron diffraction.

RadialPR.exe is a Windows executable. The executable and a few support files are located in a zipped file here and are freely available for both scientific users and the merely curious.

Running the demo: This is a specialized application designed only for particular image formats and is not self-explanatory. For demonstration purposes it can be run on the example images provided.

• After starting the application, there will be two lower panels (commonly referred to here as pages) that can import TIFF images. Click either Open then select in order signal, background and mask images: open.tif, close.tif, and mask.tif.
• After a moment of computation the signal image should be visible. Expand the working page to full screen. The concentric blue circles will generally not default to the correct image center. Enter in new values of assumedX and assumedY and right click on the image to redraw (A newer unreleased version redraws automatically.)
• Click on ComputeSymmetryImages to see the symmetric images produced by assuming the current center. Since the center is difficult to find it can be automated.
• Click on ComputeCenterSurface and after some integration time (longer if the start-end radius is large) an error measure related to the intensity of the asymmetric image is shown in a table and in a 3 dimensional grid surface.
• DeltaXY can be increased to increase the table and grid size but it also increases compute time dramatically.
• The grid page is interactive and when selected can be rotated with the arrow keys. Type 'f' to toggle thru a few shade styles of the grid. '-' and '+' will zoom. See image below. This is currently one of our oldest applications and is not self-explanatory. Contact me if you would like additional help.
• Techniques for using this specialized AlphaSquared graphical user interface can be found here.
• After an accurate center is established and entered into assumedX and assumedY, click Integrate and then some of the other pages will show the radial curve of interest. Graphs are interactive.

Note that this program is intended for experimental simulation not mass distribution. No harm can be done in running the program incorrectly, but it would not be surprising to find a bug or two in the program. (More effort was intentionally dedicated to exploration than robustness.) Due to its highly technical and exploratory nature, many features are indicated only in the source code. If you have interest in those features, please contact me.

Source code is available from the author on special request. It uses the AlphaSquared graphical user interface.

Development of this program was funded primarily by The Rowland Institute for Science, under the direction of Joel Parks. The program was written exclusively by Douglas Cameron.