N.Vischer 23-May-2018
ImageJ macro for testing the JPG quality loss for spatial measurements.
We detect the minima along radial profiles in an image with concentric rings
that are spaced at 15 pixels.
In both images (TIF and JPG), and the distances between the minima along radial profiles are measured and compared.
Measurements are performed on copies that are scaled-up by factor 10 (after JPG conversion) to get a resolution of 0.1 pixels.
Output: A table with two columns (intervalsTIF and intervalsJPG) is shown. In theroy, all values should be 15 pixels. The screenshot shows values for JPG quality=75% (which is adjustable)
Note that saving and reloading a JPG image a second time at same quality setting does not change the image contents.
Run the macro
https://sils.fnwi.uva.nl/bcb/objectj/examples/utils/JPG_Quality_Loss/JPG_Quality_Loss.txt
Test 1:
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JPG Quality: 90
Image size (K): 156.2
JPG File size (K): 26.5
Max Contrast Flag: 1
Nominal Interval = 15 pixels
intervalsTIF: StdDev = 0.1427 pixels
intervalsJPG: StdDev = 0.2061 pixels
Range TIF: = 14.6 - 15.5 pixels
Range JPG: = 14.5 - 15.8 pixels
Test 2:
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JPG Quality: 75
Image size (K): 156.2
JPG File size (K): 10.0
Max Contrast Flag: 0
Nominal Interval = 15 pixels
intervalsTIF: StdDev = 0.1453 pixels
intervalsJPG: StdDev = 0.3781 pixels
Range TIF: = 14.6 - 15.5 pixels
Range JPG: = 14.2 - 15.9 pixels