Solve for minimum and maximum value of dct coefficient

Question

I assume it happens at the DC coefficient of $C[k_1,k_2]$... Do you know where the DC coef is ? — Fat32, Dec 04 '20 at 19:53
Please write the question using LaTeX instead of posting the image. — Royi, Dec 05 '20 at 10:09

IanJ · Answer 1 · 2020-12-05T16:25:32.767

3

The max value for a DCT coefficient with this formula would be when $k_1 = 0$ and $k_2 = 0$. Using this give us the $\cos(0) = 1$ so you simply sum up the pixel values. Since the pixel values are $0-255$, then the max value is $64*255 = 16320$.

The min value can be computed by putting a pixel value of $255$ whenever the product of the cosines is negative, and a zero when it is positive. You would have to iterate through the $k_1$ and $k_2$ values to find the smallest value.

edited Dec 05 '20 at 16:25

answered Dec 04 '20 at 23:26

IanJ

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Nicely put. As DCT coefficients for JPEG are integers, some rounding can even be added on the final result – Laurent Duval Dec 05 '20 at 09:57

Solve for minimum and maximum value of dct coefficient

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