Do yourself a great favour and do not use lossy-compressed images
compression is good to store digital pictures for the Web because they are small, but it is not good at all
to do serious imaging. JPEG
compression throws away information that the eye does not see, but ImageJ will, so there is a good chance of ending up measuring artifacts instead of data (especially when analysing textures and pixel intensities). This situation is, however, avoidable: while most digital cameras save in JPEG
format by default, it is likely that they can also save images in some non-lossy format (such as TIFF
or a custom RAW format). Use those formats instead, you can convert them later to TIFF
(compressed or uncompressed) or PNG
(which was designed to achieve non-lossy compression). Be aware that once an image has been saved as compressed JPEG
there is no way of reverting to the original (so an old JPEG
-compressed image saved again as TIFF
still contains all the JPEG
compression artifacts of the original).
If you do not believe that the artifacts are there, take an RGB JPEG
-compressed image, convert it to HSB and then take a look at the blockiness especially of the Hue channel
From left to right: Jpeg compressed RGB image (original 100×155 pixels), the Hue channel, the Saturation channel and the Brightness channel.
If your papers get rejected because the referees don't like image analysis on JPEGs, don't complain!