Vignetting, discussion about methods of resolution Options

[Tman]

Hi Nirgal and all, I would like to discuss about vignetting and methods of resolution for it. I'm mainly interested in mathematical methods that could automatically calculate and adjust the right grey value for each pixel in a single picture.

My current method works with more or less transparent layers over the original picture that so roughly are able to balance the grey values. A perfect layer have to be the exact inverted brightness difference of each picture with this shadow effects. This method is very effective if you get the correct inverted values. These shots of the Mars sky come nearly at such a perfect mask, but not always. And of course the center of the pictures lose much of theirs original brightness/luminance sadly.

I have in mind a mathematical method that can adjust each grey value in a pic in order to obtain a completely balanced brightness over the entire picture. But I'm not in the position to reach that. I only know one have to start with the calculation of the grey values in the center of the picture. In the center are quasi the reference values of the whole picture, if I'm correct.
Is there a possibility (mathematical method) to get (roughly) the same brightness and luminance like in the center over the whole picture from the MERs?

Greetings, Peter

[MichaelT]

After a long, long time I am currently developing a new version of my anti vignetting tool, version 3. Again, it is based on IDL and can be used with RSI's Virtual Machine. See earlier this thread.
It is not complete, yet. The "save file" buttons are not fully functional up to now (you can't save). But, I want to give you a preview of what to expect during the next weeks. You can already play around and test it and tell me about any bugs that you find.


The program is now faster due to a much improved and simpler de-vignetting routine. Also, you can do more adjustments than in the previous versions.

Other improvements:
- You can open as many files as you like and change between them during processing (pull-down-menu).
- A '+' or '-' before each file name indicates the processing state (with or without de-vignetting).
- After processing simply choose "save all" and the program will automatically save all the files in folders designated by you.
- "Save all" will open a window with a list of all files and their current state of processing. It is planned to enable you to set output-folders for each file or copy a certain output-folder-name to a selection of files. After hitting "save", all currently processes images will be saved one after another. This could take some time as the program does not keep the whole file in its memory but just a smaller version. So it will read each file again, do the de-vignetting and save it to the destination folder.
- Like in the previous versions you can choose either jpeg or 16-bit-tiff output (or both). Do you need any other file types (png)?
- You can draw an area in the image window which will be used for the de-vignetting (by clicking with the left mouse button, set up to 64 points). Clicking close to an already present line will insert a new point. These points can be relocated by holding the left mouse button and moving the mouse. You can delete them by double-clicking (except the one in the lower left corner).
- The selcted area can be copied from one image to another.
- The de-vignetting of anaglyphs also removes the green/blue - red gradient wich often causes dark borders between image even though they vignetting has been removed.
- You can also adjust the brightness of the image (shift the whole color range or with a multiplicative factor) and the amount of vignetting.
- Clicking and holding with the right mouse button will show the unprocessed image if you have already processed it. This click will also select a line (x direction) the brightness values of which will be shown in the left hand window when changing the brightness and de-vignetting settings. That way you can optimally adjust the a-vig values.
- The histogram of the image is also shown after each change. Even though the image is shown with a pixel value cut-off of 255 then actual histogram is shown in the histogram window. Saving the file as 16-bit-Tiff will retain even those pixels which are brighter than 255.
- Moving the mouse cursor over a button will show you its function (help button is still missing).
- you can choose the type of the image (gray-scale, anaglyph, RGB) manually, though it is determined automatically when loading it. Changing the type can have the benefit that you can move the sliders for the de-vignetting and brightnes adjustment either independently or together. before saving you should set it back to the actual type.

Things I also want to implement is output of the de-vignetting or vignetting mask.

There are certainly things that I forgot to mention. Simply try it out or ask me.

So this is the time now to tell me your wishes or worries or both

The program is located here: http://www.muk.uni-hannover.de/~theusner/mars/anti_vig_n.sav

Like in the previous versions, you must not, under all circumstances, change its name

Have fun playing around with it!

Michael

[hortonheardawho]

Hi Michael,

I have been interested in your anti-vignetting program for some time -- but have resisted the HUGE ( 118 MB ) download of IDL6.3 VM.

Well, I just downloaded the VM and your new version -- but before I run the VM install I want to understand the implications.

How does the IDL VM interact with the O/S -- specifically Windows 2000?

Requirements? I am running a Pentium 4 @ 1.5 GHz with 768 MB of memory. I am a little short of disk space on C ( down to my last few GB ) but have about a 100GB free on D.

Looking forward to producing some "professional looking" panoramas utilizing your tool.

color by horticolor: more real than real.