How to cut an image using a list of points using opencv -


i have image, , selection given list of points (a poly). goal image except selection transparent.

there 2 parts question: * how create mask list of points? * what's best way of creating new image using mask? thinking of cvcopy how can handle alpha channel?

i had simillar issue , solved in strange (not fast) way:

  1. extracted red, green , blue channels of image (using extractchannel).
  2. do bitwise_and operation between each of channels , poygon mask image.
  3. merged them (using merge function).

note if have one-channel image need bitwise_and.

c++ code:

void createpoi(const mat& src, const mat& polymat, mat& dst) { vector<mat> array(3); (int i=0; i<3; i++) { extractchannel(src, array[i], i); bitwise_and(array[i], polymat, array[i]); } merge(array, dst); }

you can create polymat mask using fillpoly/fillconvexpoly functions (depends on polygon). example:

mat polymat = mat::zeros(size, cv_8uc1); fillconvexpoly(polymat, polygon, scalar(255));

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