Compare two images and mark the unmatched object or remove unmatched

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Many ways to do this, but the simple one is to use the void absdiff(InputArray src1, InputArray src2, OutputArray dst) function.

Calculates the per-element absolute difference between two arrays or between an array and a scalar.

Parameters:

• src1 – first input array or a scalar.
• src2 – second input array or a scalar.
• dst – output array that has the same size and type as input arrays.