Improve quality JPG

[programmer_ceds]

(05-04-2021, 05:35 PM)Ofnuts Wrote: Gimp knows... The first line at the top of the JPG export dialog is the option Use quality settings from the original image!!!

But is the compression level saved in the JPEG?

The GIMP function jpeg_detect_quality() contains the comments:

Code:

* Returns the exact or estimated quality value that was used to save
* the JPEG image by analyzing the quantization table divisors.
*
* If an exact match for the IJG quantization tables is found, then a
* quality setting in the range 1..100 is returned.  If the quality
* can only be estimated, then a negative number in the range -1..-100
* is returned; its absolute value represents the maximum IJG quality
* setting to use.  If the quality cannot be reliably determined, then
* 0 is returned.

Perhaps it is more correct to say "Gimp thinks it knows..."