Talk:JPEG

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JPEG was a good articles nominee, but did not meet the good article criteria at the time. There may be suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.

Article milestones
Date	Process	Result
October 28, 2007	Good article nominee	Not listed

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Wrong sizes in RLE

I believe there is a mistake in part showing the result after RLE. There are no sizes 3 (2^3) even though it is possible to fit only 6 values to sizes 1 and 2 combined (2^1+2^2), but the quantized block has 8 values (1, -1; 2, -2, -3, -4; 5, -6). This is the part:

With this in mind, the sequence from earlier becomes: (0, 2)(-3);(1, 2)(-3);(0, 1)(-2);(0, 2)(-6);(0, 1)(2);(0, 1)(-4);(0, 1)(1);(0, 2)(-3);(0, 1)(1);(0, 1)(1); (0, 2)(5);(0, 1)(1);(0, 1)(2);(0, 1)(-1);(0, 1)(1);(0, 1)(-1);(0, 1)(2);(5, 1)(-1);(0, 1)(-1);(0, 0);

I believe this is the right sequence:

(0, 2)(-3);(1, 2)(-3);(0, 2)(-2);(0, 3)(-6);(0, 2)(2);(0, 2)(-4);(0, 1)(1);(0, 2)(-3);(0, 1)(1);(0, 1)(1); (0, 3)(5);(0, 1)(1);(0, 2)(2);(0, 1)(-1);(0, 1)(1);(0, 1)(-1);(0, 2)(2);(5, 1)(-1);(0, 1)(-1);(0, 0);

Am I right or am I missing something?

——

I think so. Amplitude category appears to follow $SSSS=\lfloor log_{2}({\text{coefficient}})\rfloor +1$ . See table F.2 ^[1]. The system for calculating this isn't elaborated on very much. --Merukit (talk) 06:40, 16 June 2024 (UTC)[reply]

References

^ https://www.w3.org/Graphics/JPEG/itu-t81.pdf

Gamma correction

The article only has one sentence mention of gamma, and links to Gamma correction, but it seems that it could say a little more here. Specifically, what gamma value is commonly used in generating JPEG files. There is a mention of 8 bits vs. 11 bits, suggesting 11/8 or about 1.4, but it could give a little more detail. Gah4 (talk) 09:15, 21 March 2025 (UTC)[reply]

[1] ttps://www.w3.org/Graphics/JPEG/itu-t81.pdf

[1]