void niBlackThreshold( InputArray _src, OutputArray _dst, double maxValue,
int type, int blockSize, double delta )
{
// Input grayscale image
Mat src = _src.getMat();
CV_Assert(src.channels() == 1);
CV_Assert(blockSize % 2 == 1 && blockSize > 1);
type &= THRESH_MASK;
// Compute local threshold (T = mean + k * stddev)
// using mean and standard deviation in the neighborhood of each pixel
// (intermediate calculations are done with floating-point precision)
Mat thresh;
{
// note that: Var[X] = E[X^2] - E[X]^2
Mat mean, sqmean, stddev;
boxFilter(src, mean, CV_32F, Size(blockSize, blockSize),
Point(-1,-1), true, BORDER_REPLICATE);
sqrBoxFilter(src, sqmean, CV_32F, Size(blockSize, blockSize),
Point(-1,-1), true, BORDER_REPLICATE);
sqrt(sqmean - mean.mul(mean), stddev);
thresh = mean + stddev * static_cast<float>(delta);
thresh.convertTo(thresh, src.depth());
}
// Prepare output image
_dst.create(src.size(), src.type());
Mat dst = _dst.getMat();
CV_Assert(src.data != dst.data); // no inplace processing
// Apply thresholding: ( pixel > threshold ) ? foreground : background
Mat mask;
switch (type)
{
case THRESH_BINARY: // dst = (src > thresh) ? maxval : 0
case THRESH_BINARY_INV: // dst = (src > thresh) ? 0 : maxval
compare(src, thresh, mask, (type == THRESH_BINARY ? CMP_GT : CMP_LE));
dst.setTo(0);
dst.setTo(maxValue, mask);
break;
case THRESH_TRUNC: // dst = (src > thresh) ? thresh : src
compare(src, thresh, mask, CMP_GT);
src.copyTo(dst);
thresh.copyTo(dst, mask);
break;
case THRESH_TOZERO: // dst = (src > thresh) ? src : 0
case THRESH_TOZERO_INV: // dst = (src > thresh) ? 0 : src
compare(src, thresh, mask, (type == THRESH_TOZERO ? CMP_GT : CMP_LE));
dst.setTo(0);
src.copyTo(dst, mask);
break;
default:
CV_Error( CV_StsBadArg, "Unknown threshold type" );
break;
}
}
void sqrBoxFilterOp(Mat& src,Mat& dst)
{
int rad = depth_discontinuity_radius;
sqrBoxFilter(src,dst,CV_32F,Size(2*rad+1,2*rad+1),Point(-1,-1));
}
