GeneralisedHyperbolicStretch V2.2.0

M

Mike1485

Well-known member
I am pleased to announce the release of Generalised Hyperbolic Stretch V2.2.0.

The principal new feature in this version is the addition of a comprehensive pixel enquiry facility on the preview image. By clicking anywhere on the preview, you will see a readout for pixel values in the area you have clicked. This can be used directly to set relevant parameter values for your stretch. In this way you can design your stretches in a far more intuitive and precise way to achieve the exact results you want.

More detail on the new features is available on the GHS website (https://www.ghsastro.co.uk/v2-2-0-notes/) and via the tooltips from within the script. A tutorial video is also in the process of production and will be available shortly.

If you have the GHS repository (https://www.ghsastro.co.uk/updates/) set up in your list of managed repositories, then you will pick up the new version next time you start up Pixinsight. If you prefer to install manually, the files are available at the GHS Github repository (https://github.com/mikec1485/GHS/releases/tag/v2.2.0/).

As ever, feedback is always welcome.

Also, David Payne and I have been invited on to The Astro Imaging Channel on YouTube for a live show presenting GHS on 29 May 2022. Building on a brief explanation of the fundamentals of image stretching, we will be exposing the “secret weapons” of GHS and demonstrating how these have been implemented in the new GHS V2.2.0 to allow creation of “designer stretches”. The live show starts at 9:30pm EDT, or if that time doesn’t suit, it will be available afterwards for view at the TAIC YouTube channel (https://www.youtube.com/c/TheAstroImagingChannel/).

Happy stretching and clear skies.

Mike Cranfield
 
Mike1485 said:
I am pleased to announce the release of Generalised Hyperbolic Stretch V2.2.0.

The principal new feature in this version is the addition of a comprehensive pixel enquiry facility on the preview image. By clicking anywhere on the preview, you will see a readout for pixel values in the area you have clicked. This can be used directly to set relevant parameter values for your stretch. In this way you can design your stretches in a far more intuitive and precise way to achieve the exact results you want.

More detail on the new features is available on the GHS website (https://www.ghsastro.co.uk/v2-2-0-notes/) and via the tooltips from within the script. A tutorial video is also in the process of production and will be available shortly.

If you have the GHS repository (https://www.ghsastro.co.uk/updates/) set up in your list of managed repositories, then you will pick up the new version next time you start up Pixinsight. If you prefer to install manually, the files are available at the GHS Github repository (https://github.com/mikec1485/GHS/releases/tag/v2.2.0/).

As ever, feedback is always welcome.

Also, David Payne and I have been invited on to The Astro Imaging Channel on YouTube for a live show presenting GHS on 29 May 2022. Building on a brief explanation of the fundamentals of image stretching, we will be exposing the “secret weapons” of GHS and demonstrating how these have been implemented in the new GHS V2.2.0 to allow creation of “designer stretches”. The live show starts at 9:30pm EDT, or if that time doesn’t suit, it will be available afterwards for view at the TAIC YouTube channel (https://www.youtube.com/c/TheAstroImagingChannel/).

Happy stretching and clear skies.

Mike Cranfield
Click to expand...
Good news, thank you Mike and David!
 
Hi Mike and Dave,
Thanks for your great work on GHS! I've been working with your scripts on and off over a couple of months, and am very impressed with the concepts, and since v2.2.0 especially, the implementation and UI. I watched your TAIC presentation and am keen to continue building my knowledge and experience of the use of the script. Is there an obvious place where 'beginners' can ask embarrassingly simple/stupid questions please? I thought you might have a GHS forum over on GHSAstro.co.uk but I see you refer there to the PI and SGL forums.
In the couple of years since I began my astrophotography journey using various software, it was your TAIC lecture which first drew my attention in detail to what stretching an image does to the data. Your explanation of how we can control and develop the contrast in an image, whilst protecting against crushing bright areas or clipping image data at the dark end of the histogram, caused a real 'eureka' moment for me! You've set me reworking a number of my images, albeit slowly and step by step.....
My first 'dumb' question is about the dark end of the histogram. When I look in detail at one of my typical image stacks, there is a flat line for a good distance along the horizontal axis where there are, apparently, no image pixels. I presume that this is due to the offset I have set in my capture program. I use ZWO ASI533MC and ASI2600MC cameras at the recommended offset value of 50. So should it not be possible to detach the hyperbolic curve from the graph origin and shift the attachment point axis along to the right to the point just before the first image samples? in this way you would not be wasting useful output image values for image brightnesses where there are no pixel samples...
Thanks in anticipation for putting me straight on this or for pointing me in the right direction....
Ed
PS I've posted a similar text on SGL
 
Last edited:
Avocette said:
Hi Mike and Dave,
Thanks for your great work on GHS! I've been working with your scripts on and off over a couple of months, and am very impressed with the concepts, and since v2.2.0 especially, the implementation and UI. I watched your TAIC presentation and am keen to continue building my knowledge and experience of the use of the script. Is there an obvious place where 'beginners' can ask embarrassingly simple/stupid questions please? I thought you might have a GHS forum over on GHSAstro.co.uk but I see you refer there to the PI and SGL forums.
In the couple of years since I began my astrophotography journey using various software, it was your TAIC lecture which first drew my attention in detail to what stretching an image does to the data. Your explanation of how we can control and develop the contrast in an image, whilst protecting against crushing bright areas or clipping image data at the dark end of the histogram, caused a real 'eureka' moment for me! You've set me reworking a number of my images, albeit slowly and step by step.....
My first 'dumb' question is about the dark end of the histogram. When I look in detail at one of my typical image stacks, there is a flat line for a good distance along the horizontal axis where there are, apparently, no image pixels. I presume that this is due to the offset I have set in my capture program. I use ZWO ASI533MC and ASI2600MC cameras at the recommended offset value of 50. So should it not be possible to detach the hyperbolic curve from the graph origin and shift the attachment point axis along to the right to the point just before the first image samples? in this way you would not be wasting useful output image values for image brightnesses where there are no pixel samples...
Thanks in anticipation for putting me straight on this or for pointing me in the right direction....
Ed
PS I've posted a similar text on SGL
Click to expand...
Hi Ed
I am glad you have found GHS useful and thanks for your feedback. On sharing experience/asking questions, we have not added a forum on ghsastro.co.uk because the main astrophotography forums (including the PI forums here as well as the likes of Astrobin, Cloudy Nights, Stargazers lounge etc) are pretty active and questions posted here (or there) on GHS (or anything else) tend to be answered pretty quickly. We could rethink this if there were a big clamour for it, but personally I feel I have enough forums I try to monitor (not overly effectively given my delay in replying to you - sorry!) without adding another!

Anyway, to your question. The simplest way to remove that "flatline" is to use the "Linear Stretch" Transformation Type. If you select this in the Transformation Type dropdown selector you will be able to set a Black point for the image - this effectively, in your terminology, detaches the curve from the graph origin. The Low clip slider below the Blackpoint slider allows you to set a proportion of pixels to clip to zero. To the right of the Low clip slider is a left pointing "x" arrow - clicking on this will set the black point to the highest value that results in no clipped pixels - ie it moves the start of the transformation graph as far right as possible without clipping any of your data.

What you cannot do in GHS is combine the Linear stretch with the non-linear GHS transformation in a single step. This is a deliberate design decision as we believe it is better to separate these two transformations.

I hope this helps
Mike
 
Hi Mike, Thanks, that’s clear - using a separate linear stretch to do this.
I am still getting used to the idea of stacking several GH stretches in sequence, each to ’apply extra contrast‘ to certain sets of samples as identified using the readout reticle. It’s a powerful, precision concept, especially since each adjustment is effectively reversible later on in the process.
Your UI tools are very helpful, however, if I may be so bold, would it be possible to add extra scaling controls which would increase or reduce the movement of slider controls with respect to mouse movements? The numerical entry method allows precision changes to be made, tested, modified or undone, but doesn’t have the same intuitive feel as mouse movements provide if the rate of change could be easily adjusted.
In any case many thanks and clear skies, Ed
 
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