In my effort to completely migrate off Iris and onto PixInsight I have written a PixInsight PCL module to perform my favourite stretch, the ArcSinh stretch (a.k.a. Asinh, Hyperbolic Arcsine).
For those unfamiliar with the ArcSinh stretch, this is a method of stretching the data whilst preserving the correct colour (i.e. the original R,G,B ratios). Colour is retained from the very faintest object to the very brightest unsaturated star. This is unlike a traditional "curves" stretch where the brighter objects become desaturated (i.e. bleached) during the stretch.
The module has a standard preview window so you can interactively judge your results while playing with the sliders. I have written it within the PI PCL development environment and have built it for the 64bit Windows platform (PixInsight "Ripley").
Hopefully it is intuitive to use (there are tooltips on every control) but I'm happy to hear suggestions. It works best if the image is already background extracted and white balanced. One of the sliders will remove any residual background pedestal in the data.
In the example below you can see how the preview window is able to highlight pixels becoming negative if too much background subtraction is applied (these values will be truncated to zero when applied to the main image). Obviously I hadn't performed a proper background extraction first.
The zip file can be downloaded here: https://drive.google...R1NVcUhhY1NPbDA
Edited by sharkmelley, 10 March 2017 - 01:59 AM.