DCT and DST (+ inverse) in arbitrary dimension

Y = DCTN(X) returns the discrete cosine transform (DCT) of X.

X = IDCTN(Y) returns the inverse discrete cosine transform (IDCT) of Y.

Y = DSTN(X) returns the discrete sine transform (DST) of X.

X = IDSTN(Y) returns the inverse discrete sine transform (IDST) of Y.

X and Y can be N-dimensional.

D = DSTMTX(k) returns the k-by-k DST transform matrix.

Faster DCT2 and IDCT2 are also included in the zip file.

Enter "help dctn", "help dstn", "help idctn", "help idstn" and "help dstmtx" in the Matlab command window for complete information.

Example
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RGB = imread('autumn.tif');
I = rgb2gray(RGB);
J = dstn(I);
imshow(log(abs(J)),[]), colormap(jet), colorbar

The commands below set values less than magnitude 10 in the DST matrix to zero, then reconstruct the image using the inverse DST.

J(abs(J)<10) = 0;
K = idstn(J);
figure, imshow(I)
figure, imshow(K,[0 255])

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