Astrophotography image stretching program, astro-color-stretch, has now been updated. This new version contains a number of new features as well as a few minor error checking improvements. New users should first view the original Fast Image Stretching with astro-color-stretch post.
The new version 1.1 works the same as before but contains some new additional optional features:
- Chromatic Aberration Correction
- Star Size Reduction
- Strength Factors for both vignette and linear gradient corrections
- White Balance Adjustment
- Method for automatically finding a dark region to optimize zero sky parameters
All features of the program as well as how to run are described more fully here in the new astro-color-stretch Setup and Parameter Guide 1.1.
Version 1.1 is now available here on the Astrophotography Software Page. The previous version is also still available.
Additional Astrophotography Resources
Main Astrophotography Page
Thanks for updating the histogrambox. However, it would be nice to pick which area you want the box specifically, I may see what I need to do to adjust the script, but shouldn’t be a big deal. In terms of installing on windows, as of 13.14 python, the opencv needs to be installed without dependencies, as there is some issue.
Thanks for the feedback. I had initially also built in the option of a user selected region but removed it in favor of the cleaner auto-scan. I may add it back in on the next revision based on your inputs. You are right, in the interim, it is not too difficult to modify the code to instead specify an upper left corner (ulc) point and box height/width. I have some of the original code snippets if that might help. Just let me know.
Thanks too for the feedback on opencv with Windows.
I encountered a situation where having inputs to choose blackpoint would help — when stretching milkyway with landscape in it, the histo box gravitates to the land black point rather tha the skys, and those two can be different and often are.
Hi Dan,
You are correct—astro-color-stretch is primarily designed for full-sky images and is not designed to handle foreground elements (e.g., landscapes) particularly well. Adding a user-defined zero-sky region option is something I am including in the next version (per yours and others requests).
In the meantime, if you’re comfortable making a minor code modification, you can override and manually control the zero-sky selection to where you want. Specifically, in the def ‘select_dark_region’ at the end of the auto-scan (the line x1, y1 = min_coords) you can explicitly set your desired upper-left corner coordinates (x1 and y1) of the sampling region. Be sure to set rgbskyzero_method = 1 and define the sampling window size via ‘win_width’ and ‘win_height’ in the “User Modifiable Variables” section.
I hope that helps with the sky portion of your image. I am not sure how the overall image will look though.