DCT-2D-filter

Overlapping 2D Discrete Cosine Transform matrix (image) filter based on non-linear thresholding, written in C. The original reference of 2D-DCT transform functions (dct.c/h) unknown (from SGN-3057 course, TUT).

sigma	PSNR +- std (noisy) [dB]	PSNR +- std (denoised) [dB]	optimal threshold
5	34.15 +- 0.01	38.15 +- 0.29	12.1
10	28.14 +- 0.02	33.34 +- 0.88	36.2
15	24.61 +- 0.01	32.75 +- 0.48	39.3
20	22.14 +- 0.01	31.29 +- 0.63	57.4
25	20.25 +- 0.01	30.55 +- 0.27	68.5
30	18.73 +- 0.01	29.44 +- 0.30	78.5
35	17.45 +- 0.01	28.72 +- 0.36	100.7
40	16.38 +- 0.01	27.67 +- 0.42	105.7
45	15.45 +- 0.01	26.88 +- 0.43	126.8
50	14.65 +- 0.01	26.12 +- 0.53	145.0

Compile filter

Tested with g++ 9.3

g++ -O3 dctfilter.c dct.c -o dctfilter

Run filter

Input and output type is a 64-bit floating point single channel matrix

./dctfilter [-i inputfile] [-o outputfile] [-m nrows] [-n ncols] [-s step] [-t threshold] [-q quiet]

Run full simulations

Gaussian simulations with varying noise levels

conda create -y --name dctfilter python==3.9.0
conda activate dctfilter
pip install -r requirements.txt

python simulate.py

Mikael Mieskolainen, {2011, 2021}