Blur Detection on image capture using AVFoundation

Question

Hi I have captured image using AVFoundation and cannot able to detect blurry image.

I have tried the proposed solution in the following link: OpenCV with Laplacian formula to detect image is blur or not in iOS but it works only on the images captured using default cameraPicker.

Used:

cv::Mat finalImage;
cv::Mat matImage = [self convertUIImageToCVMat:image];

cv::Mat matImageGrey;
cv::cvtColor(matImage, matImageGrey, CV_RGBA2GRAY);
matImage.release();

cv::Mat newEX;
const int MEDIAN_BLUR_FILTER_SIZE = 15; // odd number
cv::medianBlur(matImageGrey, newEX, MEDIAN_BLUR_FILTER_SIZE);
matImageGrey.release();

cv::Mat laplacianImage;
cv::Laplacian(newEX, laplacianImage, CV_8U); // CV_8U
newEX.release();

cv::Mat laplacianImage8bit;
laplacianImage.convertTo(laplacianImage8bit, CV_8UC1);
laplacianImage.release();
cv::cvtColor(laplacianImage8bit,finalImage,CV_GRAY2BGRA);
int rows = finalImage.rows;
int cols= finalImage.cols;
int maxLap = -16777216;
unsigned char *pixels = laplacianImage8bit.data;
for (int i = 0; i < (laplacianImage8bit.elemSize()*laplacianImage8bit.total()); i++) {
    if (pixels[i] > maxLap) {
        maxLap = pixels[i];
    }
}



pixels=NULL;
finalImage.release();

BOOL isBlur = (maxLap <= kBlurThreshhold)? YES :  NO;
NSLog(@"Max: %d, Cols: %d, Rows: %d", maxLap, cols, rows);

Please note I have to resize the image in 1500 X 1500 res. before applying blur detection on it as per requirement. A helpful solution will be appreciated.

Thanks.

score 1 · Answer 1 · answered Oct 12 '19 at 16:28

iOS now supports Metal Performance Shaders, which can do this for you. There is a shader literally called MPSImageLaplacian, and then another one called MPSImageStatisticsMeanAndVariance. Apply one after the other, and you've got your "Variance of Laplacian" :). For details on how to do this, see: https://medium.com/@salqadri/blur-detection-via-metal-on-ios-16dd02cb1558

Blur Detection on image capture using AVFoundation

1 Answers1