To best retain sharpness, my preferred method of downsizing is to do so 10% at a time, otherwise known as stair stepping. Currently, after exporting full size tiff out of darktable, this can be done manually in Krita, however this is quite repetitive and time consuming, and I wonder if the process can be scripted automatically, in Krita, or other programs such as g’mic, imagemagick, graphicsmagick etc…
The process is this:
a) ( Export Width – Desired Width ) * 0.1 = Increment Size
b) Export Width – Increment Size = New Image Width
c) New Image Width - Increment Size = New New Image Width
Repeat (c) until Desired Width is reached. Then save as jpeg.
Eg.
( 3800 - 1600 ) * 0.1 = 220
3800 - 220 = 3580
3580 - 220 = 3360
etc…
It would be ideal to retain the tags and metadata of the tiff in the saved jpeg, set parameters for jpeg quality, embed color profile, and set scaling algorithm (lanczos3 preferred).
Can it be done?