"If you have a jpeg saved on your harddrive and continually open and close it then it seems possible that some data may be lost each time the file is decompressed and recompressed"
Aus,
I ran a simple test to check on the degree of degradation produced by 4 iterations of loading a JPEG file into computer memory, doing some minor editing, flattening the image, and saving it onto the HD.
A side-by-side comparison of the of the manipulated file against the original JPEG file showed that only when the image was enlarged many many times, could any degradation be observed. This agrees with the gist of your message, and also with Bruno's comment that it is a non-issue.
I have to wonder why the above is in disagreement with what I said in my message to Pam, "Yes, after I purchased my Mustek scanner a few years ago, I quickly learned that a little definition is lost each time a .jpg file is loaded and [then] saved.". "A few years ago" was maybe 10 years. My friend and I each observed appreciable degradation when JPEG files were loaded into memory and then saved to the HD. At that time I was using a different application program, but a more likely reason for the observed degradation is that the compression/decompression algorithms were inferior to what we have now.
Anyway, my post did not help Pam with her inquiry, but it did get a nice discussion going.
Sorry, Pam.
NHP |
