Originally posted by songdog:
I'm wondering how "intelligent" JPEG compression is...
[... snip ...]
My question: Is jpeg compression "smart" enough to know that I'm simply taking the original image, making 3 copies of it, rotating those copies in various ways, and then "stitching" them all together? In other words, will the resulting jpeg image be 56 KB in size, or closer to the original 14 KB?
The short, simple answer is no, it is not. However, I just did an experiment with an image to see what would happen if I took and image and did what you described (I think I understood what you're trying to do). Result? An image that had 4x the surface area was only about 2x larger. By adjusting the compression level up to around 70%, I was able to reduce the size even further without excessive image degredation. Unfortunately, a level of compression high enough to approach the original image size would result in too much degredation.
If I remember correctly, JPEG processes images in blocks and does some pretty fancy mathmatics to reduce the amount of information stored. But ultimately, it still has to read the entire image and isn't 'smart' in the way I think you were looking for.
In your case, I suspect that a 14KB original image will likely translate into a 25-30KB image after your transformation. Of course, it also depends on the overall complexity of the image. The only way to find out for sure is to experiment.