1 | function result = homogWarp(im, H, szIm, grayDefault) |
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2 | %% result = homogWarp(im, H, szIm, grayDefault) |
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3 | %% Warp the input image by the 2D homography H. The output |
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4 | %% image, result, is to be of size szIm, with x going from 0 to szIm(2) |
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5 | %% and y going from 0 to szIm(1). By default, szIm = size(im). |
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6 | %% grayDefault is the gray level to use for points in the new image |
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7 | %% that cannot be mapped from the original image im. |
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8 | %% Note, the warp H is arranged such that a pixel (x,y) in |
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9 | %% the result image comes from pixel (p1/p3, p2/p3) in the original |
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10 | %% image im, where (p1 p2 p3)^T = H * (x,y,1)^T. (If you don't get |
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11 | %% the desired result, try using the inverse of H.) |
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12 | |
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13 | if nargin < 3 |
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14 | % size of the image |
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15 | szIm = size(im); |
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16 | end |
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17 | if nargin < 4 |
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18 | % default gray value |
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19 | grayDefault = 127; |
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20 | end |
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21 | |
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22 | % pixel coordinates in original image |
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23 | [x,y] = meshgrid(1:size(im,2),1:size(im,1)); |
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24 | |
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25 | % pixel coordinates in result image |
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26 | if any(szIm ~= size(im)) |
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27 | [xp,yp] = meshgrid(1:szIm(2),1:szIm(1)); |
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28 | pix = [xp(:)'; yp(:)']; |
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29 | else |
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30 | pix = [x(:)'; y(:)']; |
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31 | end |
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32 | |
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33 | % homogeneous pixels in result frame. |
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34 | hPixels = [ pix; ones(1,prod(szIm))]; |
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35 | |
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36 | % corresponding warped points in original frame |
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37 | hScene = H*hPixels; |
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38 | |
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39 | % pixel coords in original frame. |
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40 | xprime=(hScene(1,:)./(hScene(3,:)))'; |
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41 | yprime=(hScene(2,:)./(hScene(3,:)))'; |
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42 | xprime = reshape(xprime, szIm); |
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43 | yprime = reshape(yprime, szIm); |
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44 | |
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45 | % Warping an image according to the homography |
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46 | result = interp2(x,y,im,xprime,yprime, '*linear'); |
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47 | result(isnan(result)) = grayDefault; |
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48 | result = reshape(result,szIm); |
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49 | |
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