the effect of compressing the same jpg image 600 times

Open the last saved jpeg image. Save it as a new jpeg image with slightly more compression. Repeat 600 times
phelixiansays...

Makes sense that the fractal compression used would eventually manifest as such. It's funny that the end image looks much like the grainy mandelbrot set viewers of the 90s.

Sagemindsays...

Here's some info from a seminar I had to teach "years Ago" on web graphics. These are from my notes, so I know there may some holes in the descriptions.

This format was derived and released into public domain. There are no laws or governing bodies which control or define it's use. JPG can represent any number of RGB colors up to 16.7 million. JPG Uses HSL (Hue, Saturation, Luminescence) in its compression method.

How it compresses...

1). RGB values are converted to mathematical formulas by your computer.

2). Data reduction begins using a process called sub-sampling.
-the brightness information is left alone while 1/2 of the other 2 scales are eliminated.
-they are eliminated by replacing two neighboring pixels with a single value representing their average
-this cuts the image size down by 2/3 in size.
-this also leaves the brightness intact

3). The image is partitioned into 8 blocks, using "DCT" (Direct Cosign Transform) and "Quantization"
-the changes in brightness and colors are identified and rounded off.
-(3's are rounded to 5's and 75's may be rounded to 100's)

4). Now, once all the rounding off has been done, there are a lot more standard and identical settings and values
-this allows it to compress via a standard and unencumbered "Lostless" compression method.

jimnmssays...

>>Open the last saved jpeg image. Save it as a new jpeg image with slightly more compression. Repeat 600 times.

Or you could open it once, save it with very high compression, no need to do it 599 more times.

Sagemindsays...

>> ^jimnms:
Or you could open it once, save it with very high compression, no need to do it 599 more times.


Actualy Jimnms, This is an over stated point that saving a JPG more than once is continually destroying it.

Lets say you start with say a Kodak Photo file.
-The first person takes this file, saves it as a JPG and sends it to person #2.
-Person #2 opens it, Crops it and resaves it as a JPG, then sends it back to #1.
-Number # then opens the file in Photoshop to look at it, and hits Save As, selects JPG and saves it to their USB Stick and then passes it to their designer.
- The designer then has to open the file, edit, levels, Brightness, contrast etc. and then saves it again.
-The oops' The designer realizes they wanted a fade or blend on the edge, so they open the file make the changes, and save "again"

Now that file has been JPG'ed 5 times and that's being reserved. It could get saved 2-3 more times minimum. By the time this file gets put into a layout and sent to the press, it is so badly degraded, it isn't worth using. You can't tell by looking at it on the computer screen, but you sure notice it after your very costly print job comes back.

I don't know how many times I need to emphasize to clients that I need the "RAW" file. Very often, I get, "Oh, we don't have anything other than that, we just downloaded that off our web site. Then we go back to the drawing board and we start over...

jimnmssays...

The description said "Open the last saved jpeg image. Save it as a new jpeg image with slightly more compression. Repeat 600 times." I'd like to see the same thing done, but open the image, save it with the same compression, and repeat 600 times.

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