Skip to content
An implementation of global matting algorithm for OpenCV.
Branch: master
Clone or download
Latest commit d6bbe47 Jan 14, 2015
Type Name Latest commit message Commit time
Failed to load latest commit information.
LICENSE Initial commit Jan 13, 2015 Update Jan 14, 2015
globalmatting.cpp Initial commit Jan 13, 2015
globalmatting.h Initial commit Jan 13, 2015

Global Matting

This project is built by reproducing the global matting algorithm in the CVPR 2011 paper:

He, Kaiming, et al. "A global sampling method for alpha matting." In CVPR’11, pages 2049–2056, 2011.


After evaluating the results on the alpha matting evaluation website, this implementation (with matting Laplacian as post-processing) ranks 5th in SAD and 6th in MSE (the original implementation ranks 10th in SAD and 9th in MSE). Running time is less than 1 seconds for an 800x600 image. Hence, this implementation is one of the highest ranked among the fast matting methods.



#include "globalmatting.h"

// you can get the guided filter implementation
// from
#include "guidedfilter.h"

int main()
    cv::Mat image = cv::imread("GT04-image.png", CV_LOAD_IMAGE_COLOR);
    cv::Mat trimap = cv::imread("GT04-trimap.png", CV_LOAD_IMAGE_GRAYSCALE);

    // (optional) exploit the affinity of neighboring pixels to reduce the 
    // size of the unknown region. please refer to the paper
    // 'Shared Sampling for Real-Time Alpha Matting'.
    expansionOfKnownRegions(image, trimap, 9);

    cv::Mat foreground, alpha;
    globalMatting(image, trimap, foreground, alpha);

    // filter the result with fast guided filter
    alpha = guidedFilter(image, alpha, 10, 1e-5);
    for (int x = 0; x < trimap.cols; ++x)
        for (int y = 0; y < trimap.rows; ++y)
            if (<uchar>(y, x) == 0)
      <uchar>(y, x) = 0;
            else if (<uchar>(y, x) == 255)
      <uchar>(y, x) = 255;

    cv::imwrite("GT04-alpha.png", alpha);

    return 0;


Image Trimap Alpha


MIT License.

You can’t perform that action at this time.