LabHints5 - Lab Exercise Hints(Worksheet 5: MATLAB...

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Unformatted text preview: Lab Exercise Hints (Worksheet 5): MATLAB Graphics Image and Video Formats MATLAB Graphics Image and Video Formats 1. Dithering can be implemented as follows: Load the image im = imread('lena.bmp'); Input the dithering matrix di = [0 8 2 10; 12 4 14 6; 3 11 1 9; 15 7 13 5]; Obtain image size [m n] = size(im) Repeat the matrix to same size mat = repmat(di, m/4, n/4); Map intensity to 0—16 im = im / 17; Set 1 when entry has im > mat dithered = im > mat; Show the dithered image imshow(dithered); 2. Basically follow the instructions. To load GIF image with colour map, use [im cm] = imread('parrots.gif'); where im holds indexes while cm holds colour map. To negate the image, keep the index while change cm to 255 ­cm: >> cm=1 ­cm; >> imshow(im, cm); 3. Most conversions are directly supported by MATLAB. RGB to CMYK can be implemented following the formulae in the lecture notes. 4. As described in the lectures, 4:2:2, 4:1:1 chroma subsampling can be implemented with imresize using nearest neighbour interpolation while 4:2:0 can be implemented with imresize using bilinear interpolation. 5 ­7. Follow instructions in the lab sheet. 1 ...
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