103 replies to this topic

[sharkmelley]

 

Here it looks like you are calculating luminance by giving equal weight to each color channel. By default PixInsight does not weight the channels equally when extracting luminance, as discussed in documentation of RGB Working Spaces (such as  https://pixinsight.c.../why_rgbws.html). Would you get better results by using the coefficients defined in the RGB Working Space?

 

 Hi John,

 

Thanks for this observation. I've never really played with RGBWorkingSpace, so I've taken the time to research what it does and to incorporate it into a test version of the code.  Using the RGBWS luminance coefficients when calculating the luminance does have some subtle but useful effects on the outcome of the stretch.  For instance it can be used make H-alpha pop out more from the background during the stretch.  It doesn't change the colour balance of those individual pixels but makes pixels dominated by that colour appear brighter in the stretched image.

 

I'll certainly put this in the next version so the more sophisticated user can take full advantage of it but I won't get a chance to do this for a little while.

 

Mark

Edited by sharkmelley, 22 March 2017 - 02:26 AM.

[JukkaP]

Thanks for looking my data. I had to give this a thought and read couple times. The result you got whit multiple iterations was good. Dont really understand why it works differently. And when it would not be good to do it in iterations to all images if it preserves the fainter contrast in images. Why not do it in many iterations allways as we do masked strech?

It really depends on the distribution of data in the image. The effect of applying the Arcsinh stretch in a number of iterations is to compress the highlights more but if you keep the total stretch the same (in the above example 144) then the gradient at the bottom end of the response curve will be identical.

Here's a graph that illustrates the response curve of those 3 stretches:
Arcsinh1.JPG

Changing the scale of the graph's x-axis shows that the gradient at the bottom end in each case is the same (i.e. 144):
Arcsinh2.JPG

Some images will respond very well to having their highlights extremely compressed - especially if the highlights only contain stars. Your image was an example of that.

Mark

The 3.5 strech looks like normal histogram transformation. While preserving star colour. Looks to me that this multiple iteration aproach should be ingluded to the aplication. You might get the code from masked strech, if you are interested in that.

I did some testing and when you adjust the background slider litle bit from the suggested one, you will have some room in your histograms left side. I did see some clipping using the automated background value.

Enyway great aplication and thanks for sharing!

[federico bonino]

Mark Good tool !

Thanks very much to share.

I Must to check it asap !!

Federico

Edited by federico bonino, 25 March 2017 - 12:27 PM.

[jammeymc]

Very nice - my new favorite stretching tool. Thank you for the all you did to provide this.

[Diane Miller]

I've been following this discussion sporadically and wondering if there is a summary tutorial for those of us who are new at this sort of thing.  I would also find it helpful to have information about the sort of image for which it is more advantageous than the usual PI process.

[Islandwatcher]

I am very interested in this topic but am fairly new to Pixinsight , have a Macbook that I use for processing and was after a few tips how to actually get this process working / installed into my version of Pixinsight...

 

Thanks

 

Steve .

[sharkmelley]

Below are the instructions for installing it under Windows.  I'm guessing guess that for the Mac you simply substitute Arcsinh-pxm.dylib for Arcsinh-pxm.dll

 

Installation instructions for Windows:

• Put Arcsinh-pxm.dll in a chosen folder.  For Windows this might be C:/Program Files/PixInsight/bin but you can choose anywhere convenient to you.

• In PixInsight navigate the Menus to: Process->Modules->Install Modules

• Use the "Browse..." button on the top right of the "Install Menus" dialog to navigate to your chosen folder and then hit the "Select Folder" button.  The name of your folder will appear as the "Search Directory".  Now hit the "Search" button.  If more than one module appears you may want to to double-click the irrelevant ones, leaving a green tick only against Arcsinh-pxm.dll

• Hit the "Install" button.

• The Arcsinh process will now be available from the Process Explorer window or the Process menu in the usual way.

Mark

[Islandwatcher]

Hi Mark ,

 

OK thanks...that seems to have done the trick...thanks for the extra clarification . I've had a quick play and it really does preserve the colours very well ! Many thanks to you...and John for this tool !

 

Steve .

[sharkmelley]

For those of you using the Arcsinh module, be warned that if you upgrade to PixInsight 1.8.5 then the module refuses to install.  Under Windows it causes a PCL Win32 System Exception dialog box when you attempt to install.

 

I don't yet know the reason for this but I'm guessing I probably need to upgrade some component in order to build a compatible module.

 

I'll keep you informed of progress.

 

Mark

Edited by sharkmelley, 05 August 2017 - 02:50 AM.

[psandelle]

Yeah, just found that it won't install with 1.8.5. Bummer; I wanted to try it. Will wait, but I was chompin' at the bit.

 

Paul

[ChrisWhite]

Really good stuff Mark.  I just installed and had a go with it.  It's much better than masked stretch, and could replace that tool as far as I'm concerned.   This process does a remarkable job retaining color saturation while stretching and star color and size was handled well.  I found that multiple passes seems to work best.  One thing I'm trying to figure out is how to achieve a little more contrast.  I'm sure with some more fiddling I'll get there, but initial impression is great. 

 

Thank you!

[sharkmelley]

In PixInsight 1.8.5 the version of the API (application programming interface) was updated from 155 to 160.  This required the module to be recompiled with the new version of the PCL (PixInsight Core Library).  At the same time the version of Microsoft Visual Studio used for compilation has been moved from MS VS Express 2013 to MS VS Community 2015.

 

So it took me longer than expected to produce a new version.

 

Anyway here's a link to the Windows version of Arcsinh 1.03 compatible with PI 1.8.5:

https://drive.google...QksyRFRnTmtMYlE

 

This newer version will not run on earlier version of PixInsight. So for completeness here's the link for Arcsinh 1.03 on earlier versions of PI.

https://drive.google...amxpVDJXSndRc0E

 

Mark

[psandelle]

Cool!

 

Paul

[hansheiser]

Hello,

 

first of all, excuse my bad English !

 

I can't get any of the Arcsinh modules installed. I'm on version 1.8.4x and tried all of the older module releases I could find. Pixinsight always gives me following error message:

 

 

My OS is Win7 Ultimate SP1 x64, Admin account. I changed permissions to full control to all users:

 

 

What else must I do? I don't want to upgrade Pixinsight to v1.8.5 by now. Too many bugs ...

 

Thank you in advance,

 

hansheiser

[sharkmelley]

Which version of PI 1.8.4 are you using?  It looks like your PixInsight is using an earlier version of PCL (version 151).  Those earlier Arcsinh modules were built using version 155 and will not work on earlier versions.

 

My version is 01.08.04.1195 works quite happily because it uses version 155 of the PCL.  Is it possible for you to upgrade to a later version of 1.8.4?  However I don't think it is available for downloading.

 

Mark

[hansheiser]

Hello Mark,

 

I'm on v 01.08.04.1171. So you mean, earliest version to use arcsinh is 01.08.04.1195, right? Updating will be no problem as I have all versions and updates on my hdd (I always downloaded any update availlabe).

 

Thank you for your fast response.

 

 

Hannes

Edited by hansheiser, 10 August 2017 - 03:53 AM.

[sharkmelley]

Yes, updating to 01.08.04.1195 is probably the best idea..

 

Mark

[federico bonino]

Hi Mark !!

 

I had a problem trying to install Arsinh in new Px version 1.8.5  

 

Do you Know what happend? or what I have to do

 

Many thanks by your help!

Federico

 

 

Attached Thumbnails

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[federico bonino]

In PixInsight 1.8.5 the version of the API (application programming interface) was updated from 155 to 160.  This required the module to be recompiled with the new version of the PCL (PixInsight Core Library).  At the same time the version of Microsoft Visual Studio used for compilation has been moved from MS VS Express 2013 to MS VS Community 2015.

 

So it took me longer than expected to produce a new version.

 

Anyway here's a link to the Windows version of Arcsinh 1.03 compatible with PI 1.8.5:

https://drive.google...QksyRFRnTmtMYlE

 

This newer version will not run on earlier version of PixInsight. So for completeness here's the link for Arcsinh 1.03 on earlier versions of PI.

https://drive.google...amxpVDJXSndRc0E

 

Mark

Excuse me Mark I did not saw your post.

I had did it succefully !!!

 

Many Thanks!

Federico

[AgilityGuy]

Mark,

 

Thanks very much for developing the module.  Clearly it was a needed tool that has worked well.  

 

I've been following this thread and haven't gotten around to installing the newest Pixinsight version or the arcsinh stretch tool. Now I have the time, will the updated version of Arcsinh install onto a Mac using the quoted method after I update my version of Pixinsight?

 

 

Below are the instructions for installing it under Windows.  I'm guessing guess that for the Mac you simply substitute Arcsinh-pxm.dylib for Arcsinh-pxm.dll

 

Installation instructions for Windows:

• Put Arcsinh-pxm.dll in a chosen folder.  For Windows this might be C:/Program Files/PixInsight/bin but you can choose anywhere convenient to you.

• In PixInsight navigate the Menus to: Process->Modules->Install Modules

• Use the "Browse..." button on the top right of the "Install Menus" dialog to navigate to your chosen folder and then hit the "Select Folder" button.  The name of your folder will appear as the "Search Directory".  Now hit the "Search" button.  If more than one module appears you may want to to double-click the irrelevant ones, leaving a green tick only against Arcsinh-pxm.dll

• Hit the "Install" button.

• The Arcsinh process will now be available from the Process Explorer window or the Process menu in the usual way.

Mark

[sharkmelley]

 

Mark,

 

Thanks very much for developing the module.  Clearly it was a needed tool that has worked well.  

 

I've been following this thread and haven't gotten around to installing the newest Pixinsight version or the arcsinh stretch tool. Now I have the time, will the updated version of Arcsinh install onto a Mac using the quoted method after I update my version of Pixinsight?

 

 

 

Unfortunately the new PixInsight will need a new module built for the Mac and I don't have the means to do that (I only have Windows machines).

 

In the medium term I'm hoping that Arcsinh will become part of the standard PixInsight distribution.  I have a bit of new functionality to add to it first.

 

Mark

Edited by sharkmelley, 25 August 2017 - 04:53 PM.

[ChrisWhite]

I hope it gets added as well.  I've been fiddling with it on Nebula as well as dark and dusty images.  I'm so impressed with how well color saturation is retained in the stretch.  An iterative approach with arcsinh followed by a little nudge from HT seems to work really well. 

 

Super module here Mark!!! 

[psandelle]

Huh, did anyone else have Archsinh vanish after the last big update?

 

Paul

[sharkmelley]

Huh, did anyone else have Archsinh vanish after the last big update?

 

Paul

That's right, it will vanish because it's not part of the official distribution for PixInsight.  So you'll need to pick up the new Windows version of Arcsinh (there's not yet a new version for the Mac) and follow its installation instructions.

 

Hope that helps.

 

Mark

[psandelle]

Right. That's what I thought, but haven't gotten around to it yet.

 

Thanks,

 

Paul