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    <p>Good one!</p> <h3>First step:</h3> <p>Compute the size of the rectangle</p> <pre><code> width = sqrt( sum( (b-a).^2 ) ); height = sqrt( sum( (c-b).^2 ) ); </code></pre> <h3>Second step:</h3> <p>Compute an affine transformation from <code>a</code>...<code>d</code> to an upright image</p> <pre><code> Xin = [a(2) b(2) c(2) d(2)]; Yin = [a(1) b(1) c(1) d(1)]; Xout = [width 1 1 width]; Yout = [1 1 height height]; A = [Xin;Yin;ones(1,4)]'; B = [Xout; Yout]'; H = B \ A; % affine transformation </code></pre> <p>Note that despite the fact that we allow fo <code>H</code> to be affine, the choise of corners (depending on <code>width</code> and <code>height</code>) will acertain that <code>H</code> will not distort the cropped rectangle.</p> <p>optionally use <a href="http://www.mathworks.com/help/images/ref/cp2tform.html" rel="nofollow"><code>cp2tform</code></a>:</p> <pre><code> H2 = cp2tform( [Xin;Yin]', [Xout;Yout]', 'nonreflectivesimilarity' ); </code></pre> <h3>Third step</h3> <p>Use the transformation to get the relevant image part</p> <pre><code> thumb = tformarray( img, maketform( 'affine', H' ), ... %//' makeresampler( 'cubic', 'fill' ), ... 1:2, 1:2, ceil( [height width] ), [], 0 ); </code></pre> <p>optionally use <a href="http://www.mathworks.com/help/images/ref/imtransform.html" rel="nofollow"><code>imtransform</code></a>:</p> <pre><code> thumb = imtransform( img, H2, 'bicubic' ); </code></pre> <hr> <h3>A note regarding vectorization:</h3> <p>depends on how the coordinates of the corners are stored (<code>a</code>...<code>d</code>) the first two steps can be easily vectorize.</p>
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    1. POHow to crop and rotate an image to bounding box?
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    1. COAre you sure that affine transformation is a good option? Affine transformation does NOT necessarily preserve angles or lengths. I would like the angles & lengths to be preserved.
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    2. CO@PrernaChikersal this is why we have the first step - making sure aspect ratio is preserved.
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    3. COpreserving the aspect ration is one thing, however the lengths will vary right? What are the pros/cons of using ur method compared to the other answer?
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