JPEG Compression Effects JPEG Compression EffectsJPEG images are much smaller than pixel arrays, and so are more suitable for viewing over a network, but JPEG compression is not a lossless method. There are differences between the restored JPEG image and the original image.
| filename | file size |
|---|---|
| face1.img | 61,632 (248 x 248) |
| face1.gif | 56,451 (lossless) |
| face_75.jpg | 10,446 (75% quality |
JPEG compression is controlled by a quality parameter expressed in percent. Higher quality settings have better fidelty but less compression
| (%) | file size | max_dev | min_dev | rms_dev |
|---|---|---|---|---|
| 75% | 10,446 | 34 | -36 | 4.871 |
| 15% | 3,413 | 76 | -68 | 9.458 |
| 10% | 2,637 | 101 | -94 | 10.859 |
| 5% | 1,890 | 128 | -116 | 14.141 |
| 75% | 15% | 10% | 5% |
|---|---|---|---|
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Differences are most noticeable beginning with bitplane 4
| before JPEG | after JPEG | |
|---|---|---|
 |  | 7 |
 |  | 6 |
 |  | 5 |
 |  | 4 |
 |  | 3 |
 |  | 2 |
 |  | 1 |
 |  | 0 |
Maintained by John Loomis, last updated Feb 15, 1997
