I understand that starnet++ works best by applying a mild stretch, which is then (I thought) reversed upon completion of star removal. But if I save the post starnet image and open it in a different program, the image is obviously still stretched. Is there a simple way to save out the linear starless image within Siril?
If you apply starnet with Siril on a linear image by checking the option for linear image, the output will be linear again.
So we would like to see screenshots to understand why you say your image is not linear.
That is certainly what I expected. The console says:
20:34:48: StarNet: linear mode. Applying Midtone Transfer Function (MTF) pre-stretch to image.
20:34:48: Applying MTF with values 0.000000, 0.000557, 1.000000
20:34:48: StarNet: Reading input image… Done!
20:34:48: StarNet: Bits per sample: 16
20:34:48: StarNet: Samples per pixel: 3
20:34:48: StarNet: Height: 4016
20:34:48: StarNet: Width: 6024
20:34:49: StarNet: Restoring neural network checkpoint… Done!
20:34:49: StarNet: Total number of tiles: 384
20:35:37: StarNet: linear mode. Applying inverse MTF stretch to starless image.
20:35:37: Applying inverse MTF with values 0.000000, 0.000557, 1.000000
20:35:37: Saving FITS: file D:\astro\C20_Lu_2024\starless_Unsaved compositing result.fit, 3 layer(s), 6024x4016 pixels, 32 bits
20:35:37: Saving FITS: file D:\astro\C20_Lu_2024\starmask_Unsaved compositing result.fit, 3 layer(s), 6024x4016 pixels, 32 bits
20:35:37: StarNet: job completed.
20:35:37: Execution time: 49.89 s
showing the reverse MTF being applied. But starless_Unsaved compositing result.fit looks like this when re-opened in Siril:
or in a different program (StarTools, in this case):
