The image below from Logic Masters India Marathon 2016 is puzzle "Twins Co-Ordinates" with PDF password of "TCO_cLiEsh".
The challenge is to find the six matching image squares given a [612,1078,3] PNG file screen captured using Snipping Tool. The matching squares may be rotated but are not reflected. The cells will not match perfectly and the PNG file is oversize into the white around the whole black frame. The image grid is 10x18. Return a 6x4 array of [r1,c1,r2,c2;...] where cell [r1,c1] is a match for [r2,c2] with r(1:10) and c(1:18). A pscript to obfuscate the solution is implemented. The method for creating a Cody pscript is included in the Test Suite.
Method Hints: Merge into a BW 612x1078 image;Trim outer white space;Locate Top Left corner of each cell;create cell array of 180 squares;grab only 55x55 squares to enable rotation check;Problem size is only 4*180*179/2;Filter positive and negative deltas separately with a + convolution; check residual delta < threshold.
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Solution 889756
Tim created another superb solution. The highlights are an elegant center of square's determination using ndgrid. The crux of his method is a convolution for each square not using "same" with an interesting centroid kernel. The comparison between all square convolutions for all rotations utilizes a concise norm metric function. The method should work on non-binary images. The best six matches from the 180x180 upper triangle error array are handily converted into the output format. Thank You Tim for this elegant solution.