Further to My Previous Blog, rgd RVSF

I got in touch with Dr. Nalin Samarasinha at PSI, who wrote the codes for all of the special cometary processing filters at PSI website. He has beeing patiently answering every of my questions so I now can understand what his RVSF code is basically doing, though I know very little of FORTRAN. The discrepancy I spot between the source code and the explanation file is indeed a typo.

I added a new keyword to my IDL routine so that the user could have the option whether they like to switch on or off the function of sub-pixel sampling of the image prior to the function of the filter or not. Through some simple tests I realized that the differences between sub-pixelization and non-sub-pixelization of the image would not be very obvious in terms of visual inspection. However, the speed matters considerably, especially when the input image size or the part of regions selected is quite large — the processing time, in this case, could be quite consuming. So it’s a good idea to preview the enhanced image without sub-pixel sampling, not only would you save a great amount of time, but also this would give you a basic knowledge about if your kernel parameters are appropriate, and finally, to process the image by sub-pixelization with reasonable kernel parameters.

I couldn’t discern any difference in the enhanced images with or without sub-pixelization, however, a subtraction between the two clearly reveals what is previously hidden behind. See the following image.

The difference between non-sub-pixelization and sub-pixelization sampling. Linear stretch.
The difference between non-sub-pixelization and sub-pixelization sampling. Linear stretch.

Additionally, I’m very delighted to find that the resulting enhanced image processed by means of sub-pixelization shares great similarity with the one processed through Nalin’s code or PSI’s online tool. So I think my routine is quite successful.

At last, before the end of this update, I need to confess that I had mistakenly regarded the author of the source codes to be Padma Yanamandra-Fisher. I had been confused by their names, all look rather long for me… ><

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Further to My Previous Blog, rgd RVSF

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