Prashant Kumar answered . 2024-05-17 21:40:52

   out = imwarp(I,tform);

is not the same as the algorithm used by imtransform syntax:

   out = imtransform(I,tform);

    % Read and display image
    I = imread('pout.tif');
    imshow(I);

    % Create geometric transformation
    T = [1 -sin(pi/4) 0; sin(pi/4) 1 0; 0 0 1];
    tform = maketform('affine', T);

    % Define input spatial referencing
    udata = [-1 1];
    vdata = [-1 1];

    % Define output spatial referencing
    xdata = [-0.8 0.8];
    ydata = [-0.8 0.8];
    output_size = round(size(I)/8);

    % Apply geometric transformation to image
    J = imtransform(I, tform, 'UData', udata, 'VData', vdata, ...
        'XData', xdata, 'YData', ydata, 'Size', output_size);

    % Display transformed image
    imshow(J)

In R2013a, this can be rewritten using imwarp, geometric transformation objects, and spatial referencing objects:

    % Read and display image
    I = imread('pout.tif');
    imshow(I);

    % Create geometric transformation object
    T = [1 -sin(pi/4) 0; sin(pi/4) 1 0; 0 0 1];
    tform = affine2d(T);

    % Define input spatial referencing. World limits of input image are from
    % -1 to 1 in both X and Y directions.
    RI = imref2d(size(I),[-1 1],[-1 1]);

    % Define output spatial referencing. World limits out output image are
    % from -0.8 to 0.8 in both X and Y directions. Output grid size is 1/8
    % that of the input image.
    Rout = imref2d(round(size(I)/8),[-0.8 0.8],[-0.8 0.8]);

    % Apply geometric transformation to image
    [J,RJ] = imwarp(I,RI,tform,'OutputView',Rout);

    % Display transformed image
    imshow(J,RJ)

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