Function extract_feature_pixel_values

dlib/image_processing/shape_predictor.h:238–281

        template <typename image_type, typename feature_type>
        void extract_feature_pixel_values (
            const image_type& img_,
            const rectangle& rect,
            const matrix<float,0,1>& current_shape,
            const matrix<float,0,1>& reference_shape,
            const std::vector<unsigned long>& reference_pixel_anchor_idx,
            const std::vector<dlib::vector<float,2> >& reference_pixel_deltas,
            std::vector<feature_type>& feature_pixel_values
        )
        /*!
            requires
                - image_type == an image object that implements the interface defined in
                  dlib/image_processing/generic_image.h 
                - reference_pixel_anchor_idx.size() == reference_pixel_deltas.size()
                - current_shape.size() == reference_shape.size()
                - reference_shape.size()%2 == 0
                - max(mat(reference_pixel_anchor_idx)) < reference_shape.size()/2
            ensures
                - #feature_pixel_values.size() == reference_pixel_deltas.size()
                - for all valid i:
                    - #feature_pixel_values[i] == the value of the pixel in img_ that
                      corresponds to the pixel identified by reference_pixel_anchor_idx[i]
                      and reference_pixel_deltas[i] when the pixel is located relative to
                      current_shape rather than reference_shape.
        !*/
        {
            const matrix<float,2,2> tform = matrix_cast<float>(find_tform_between_shapes(reference_shape, current_shape).get_m());
            const point_transform_affine tform_to_img = unnormalizing_tform(rect);

            const rectangle area = get_rect(img_);

            const_image_view<image_type> img(img_);
            feature_pixel_values.resize(reference_pixel_deltas.size());
            for (unsigned long i = 0; i < feature_pixel_values.size(); ++i)
            {
                // Compute the point in the current shape corresponding to the i-th pixel and
                // then map it from the normalized shape space into pixel space.
                point p = tform_to_img(tform*reference_pixel_deltas[i] + location(current_shape, reference_pixel_anchor_idx[i]));
                if (area.contains(p))
                    feature_pixel_values[i] = get_pixel_intensity(img[p.y()][p.x()]);
                else
                    feature_pixel_values[i] = 0;
            }
        }

    } // end namespace impl