Well, i wonder, what compression procession processes they are using.. I uploaded a test image of 2.3mb and suddenly downloaded it
It was only only 92 kbs, what the heck, only 92 kb's and the thumbnail was only 11 kbs..
How this all is done and what algorithms are utilized.. how do i do it..
If I had to guess, the file size decrease is probably due primarily to just old-fashioned downsampling. Images on facebook are sized to be viewed on part of a screen, but not much larger.
For instance, I uploaded a picture that was 3456x2304 (3.2MB) which is 7,962,624 pixels. This was downsized by facebook to 960x602 (85kB) which is only 577,920 pixels. That only about 1/14th the total number of pixels.
This probably explains the majority of the difference, but it also looks like they are using the sRGB color profile, which can reduce file sizes.
One other possibility is that most JPEG encoders have a quality setting. They may be using a lower quality setting than that of the original.