Starmask & Previews

[Simon Hicks]

Hi PI Guys,

If I create a small Preview in an image, and then select the Preview, and then create a Starmask of the Preview, then it takes just as long to calculate the Starmask as it does for the whole image.

If however I copy the Preview and then paste it as a new image then it takes approx 1 second to create a Starmask.

Is there something wrong with the way that Starmask is creating a starmask of a Preview, or am I doing something wrong?

Regards
                Simon

[Juan Conejero]

Hi Simon,

This is not a bug; it's normal behavior of the StarMask process.

Unfortunately, the StarMask algorithm needs to work with the whole image as part of the necessary procedure to generate a meaningful preview. So the performance gain achieved by trying out this process on a small preview is pretty small.

This is because this process performs some wavelet and morphological transformations that depend on large-scale image structures that cannot be ignored when generating a preview on a small area. We have ideas to improve these limitations, but it isn't easy to overcome them completely.

We have developed a technique that combines HDRWaveletTransform and StarMask that greatly facilitates generating star masks, even in extremely difficult situations. Take a look at the material I included in this thread:

http://pixinsight.com/forum/viewtopic.php?p=2830#2830

As you can see in this example, the combined technique is really powerful and makes StarMask much more efficient and easy to use. If you decide to try it, I'll be very interested in looking at your results.

[Simon Hicks]

Hi Juan,

"If you decide to try it...".....of course I will try it !   :lol:

Thanks for the explaination Juan, that certainly makes sense. It will be a few days before I can try the algorithm....travelling at the moment....but I will try it and get back to you will comments. I'm always excited to try any new feature.

Cheers
         
Simon

[Simon Hicks]

Initial response.....ooooo....that's clever!  

Definitely one to remember and keep in the tool box.

Cheers
         
Simon