JPG facts & stats

Question 1

What does JPEG stand for?

Accepted Answer

Joint Photographic Experts Group. JPEG is named after the Joint Photographic Experts Group, the committee that created the standard.

Question 2

Which kind of image is JPEG best suited for?

Accepted Answer

Photographs with smooth color changes. JPEG compresses photos with gradual color changes very well, but can blur sharp text and line art.

Question 3

Early DOS and Windows file names limited extensions to how many characters, which is why '.jpg' is common?

Accepted Answer

3. Old 8.3 file names allowed only three-letter extensions, so '.jpeg' was shortened to '.jpg'.

Question 4

Standard JPEG images do not support which feature that PNG and GIF images do?

Accepted Answer

Transparency. Baseline JPEG has no transparency channel, so formats like PNG are used for images with see-through areas.

Question 5

How many bits per color channel does a standard baseline JPEG use?

Accepted Answer

8. Baseline JPEG uses 8 bits per channel, giving 256 possible levels in each channel.

Question 6

Which mathematical transform is at the heart of standard JPEG compression?

Accepted Answer

Discrete cosine transform. JPEG converts image blocks with the discrete cosine transform; the later JPEG 2000 uses wavelets.

Question 7

In which year was the first JPEG standard published?

Accepted Answer

1992. The original JPEG standard, ITU-T T.81, was published in 1992.

The basics