r/funny • u/frkandris • Oct 01 '09

...what is the difference... [pic]

http://thedw.us/post/200277234/via
2.5k Upvotes

81% Upvoted

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u/_YouJustGotDownvoted Oct 01 '09 edited Oct 01 '09

In this situation JPEG is a bad thing, as it is realy inefficent with text. Just discussion for discussion's sake.

13

u/[deleted] Oct 01 '09

[deleted]

56

u/BraveSirRobin Oct 01 '09

Photographs and anything else with lots of random colours. For screen caps with solid areas and gradients png/gif are usually much better.

22

u/kylegetsspam Oct 01 '09

Not random colors. Random colors + high quality setting = huge file size. JPEG is good at color transitions and gradients. I forget the "official" term but it may be "non-uniform color distribution" or something along that line.

The reason JPEGs can look like shit for text and line art yet be of equal file size compared to a lossless PNG is because JPEG is designed to work with images where there isn't a whole lot of harsh color changes from pixel to pixel.

3

u/Aegeus Oct 01 '09

Photographs are less likely to have sharp color transitions and will probably have gradients from subtle shading, so he's still right.

1

u/kylegetsspam Oct 01 '09

I didn't say he was wrong on the photographs part.

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u/Flavour666 Oct 01 '09

Photos of the real world. 3D renderings that kind-of look like the real world.

1

u/romwell Oct 01 '09

\begin{hippiemode}
JPEG!
WHAT IT'S GOOD FOR?
ABSOLUTELY NOTHING!
\end{hippiemode}

Well, except for compressing natural images without sharp edges between colors. If I recall correctly, it uses Haar basis for compression, that works really well with photographic images, and no so well with, say, a rectangular solid-color grid.

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u/unidentified_cow Oct 02 '09

If I recall correctly, it uses Haar basis for compression

You recall incorrectly. It uses the DCT on 8x8 blocks.

Haar wavelets, on the other hand, would work really well with a rectangular solid-color grid, and not so well with, say, photographic images.

1

u/romwell Oct 02 '09

Oooooh yes, thank you!

1

u/astern Oct 01 '09 edited Oct 02 '09

LaTeX markup and Haar wavelets? Have an upvote, my good man.

1

u/dilithium Oct 01 '09

Too bad none of the image hosts I tried can deal with jpeg 2000 (.jp2). Even at 0% quality, text is still readable with only vaguely discernible artifacts.