Chapter 11.2, Problem 3CP

Obtain a grayscale image file of your choice, and use the imread command to import into MATLAB. Crop the resulting matrix so that each dimension is a multiple of 8. If necessary, converting a color RGB image to gray scale can be accomplished by the standard formula (11.15).

a. Extract an $8\times 8$

pixel block, for example, by using the MATLAB command xb=x(81:88, 81:88). Display the block with the imagesc command.

b. Apply the 2D-DCT.

c. Quantize by using linear quantization with $p=1,2$, and 4, Print out each $Y_Q$

.

d. Reconstruct the block by using the inverse 2D-DCT. and compare with the original. Use commands MATLAB colormap(gray) and imagesc(X [0 255]).

e. Carry out (a)-(d) for all $8\times 8$ blocks, and reconstitute the image in each case.