Getting Started: Concepts

[andyschlei]

I came across PixInsight on recommendations from the Yahoo! CCD New Astro group while looking for noise reduction software.  I found a tremendously flexible tool that I don't have the underlying knowledge to fully exploit or even use effectively.  The tutorials are good, but there are clearly underlying concepts that I don't know that would help me better utilize the software.

Can anyone recommend books or links that discuss the underlying image processing concepts utilized in the software?

A primer would be nice but I'd wade through a difficult text.

I'll even expose the depth of my ignorance.  Wavelets in Registax sharpens the image.  The wavelets in PixInsight blur it.  But it is clear that the blurring is only a step in an unsharp masking process -- so Registax must be doing two steps where PixInsight does one.  But I don't have the knowledge to know what the next steps are.

Thanks in advance,

--Andy

[Carlos Milovic]

Hi Andy :)

The first thing that you should know about PixInsight's paradigma is that you have control over almost everything. That means, we sacrifice user friendly interfases with advanced controls, so you may fine tune the parameters, and reach eventually better results. Regarding your wavelets doubt, first you must know what a wavelets are: it is just a decomposition of the image into several layers, wich each one of them contains details of the image between a defined range of scales. In simple words, to give an example, with wavelets you may split an image of a galaxy into 3 layers, were the first one contains stars and other high frecuency features, the second shows the spiral arms, and the last one gives you the large scale form of the galaxy. Now, you may work with each of the scale components individually.
After that introduction, our A Trous Wavelets process allows you to change the way all the scales are merged again. If you disable a layer, you blur the image, becouse some details are lost. If you increase the bias, you increase the contrast of that layer, and then you are sharpening those scales. It is a matter of trial and error to find out the best values for your image.

Now, regarding documentation... We know we lack a complete documentation, and many tutorials, specially for people who is not familiar with image processing techniques. Meanwhile, I recommend you to read our online tutorials, and just play with your images to see what happens. Also you should read PixInsight LE's official documentation, wich may be a good introduction to many processes on our standard edition.

Regarding printed books, take a look at "Digital Image Processing" by Gutierrez (it was an spanish name, but it writen in inglish). It is general book, that cover all the basis, applied to almost every field of today's image processing. Another good book, but less "formal", and more oriented to users than to teach the basics, is "The Handbook of Astronomical Image Processing" by Richard Berry and James Burnell. There are many other books, more oriented to astronomy, but they ussually goes around Photoshop, and you'll quickly surpass their level. Just tell you tricks, but not a good knowlegde on what you are doing.


Finally, of course, you have this forum. We'll happilly answer your questions. Just remember to search the answer in older posts, so you don't repeat topics.

[andyschlei]

Carlos,

Thanks for the quick reply.

The first thing that you should know about PixInsight's paradigma is that you have control over almost everything. That means, we sacrifice user friendly interfases with advanced controls, so you may fine tune the parameters, and reach eventually better results.

That is what excites me so much about the software.  It not only allows fine control, but relies on a true understanding of what is being done.  So, for me, it will be a tool for learning about image processing.

Meanwhile, I recommend you to read our online tutorials, and just play with your images to see what happens. Also you should read PixInsight LE's official documentation, wich may be a good introduction to many processes on our standard edition.

I will do that.  The tutorials I have been through so far have been good, but I am hampered by not understanding the underlying theory.

Regarding printed books, take a look at "Digital Image Processing" by Gutierrez (it was an spanish name, but it writen in inglish). It is general book, that cover all the basis, applied to almost every field of today's image processing.

Do you mean Digital Image Processing by Gonzales and Woods?

There are many other books, more oriented to astronomy, but they ussually goes around Photoshop, and you'll quickly surpass their level. Just tell you tricks, but not a good knowlegde on what you are doing.

That is very true.  Good techniques, but no explanation about why it works.  It took a presentation from David Malin at AIC before I saw any explanation of the simple concept of an unsharp mask!

Thanks again for your help.  I am ordering at Willman-Bell and Amazon right now!

--Andy

[Carlos Milovic]

Hi Andy

Yes, sorry... the author is Gonzales I knew it was an spanish last name . Be sure you get the latest edition (second or third, I can´t remember), becouse it introduces a chapter on wavelets. Just to let you know how is used this book, I´ll tell you that it was the text book that was used in the Image Processing course I followed at the university.

It took a presentation from David Malin at AIC before I saw any explanation of the simple concept of an unsharp mask!

Not very simple, but I assume that it will be explained at the book, in the chapter about Convolutions. UnSharp Mask is just a way to implement a high pass filter (you´ll know what that means).


Well, as I told you, here we are to answer your questions, and I´ll be specially glad if they are about image processing itself