Bilinear Interpolation

[unrealwill]

I was reading your code, and noticed that the Bilinear interpolation is not doing what we usually called Bilinear interpolation, (but something that look like a usual mistake).

dvo/dvo_core/src/core/interpolation.cpp

Lines 36 to 53 in bd21a70

	IntensityType Interpolation::bilinear(const cv::Mat& img, float x, float y)
	{
	int x0 = (int) std::floor(x);
	int y0 = (int) std::floor(y);
	int x1 = x0 + 1;
	int y1 = y0 + 1;
	float x_weight = x - x0;
	float y_weight = y - y0;
	float interpolated =
	img.at<IntensityType>(y0, x0) * x_weight + img.at<IntensityType>(y0, x1) * (1 - x_weight) +
	img.at<IntensityType>(y1, x0) * x_weight + img.at<IntensityType>(y1, x1) * (1 - x_weight) +
	img.at<IntensityType>(y0, x0) * y_weight + img.at<IntensityType>(y1, x0) * (1 - y_weight) +
	img.at<IntensityType>(y0, x1) * y_weight + img.at<IntensityType>(y1, x1) * (1 - y_weight);
	return (IntensityType) (interpolated * 0.25f);
	}

https://en.wikipedia.org/wiki/Bilinear_interpolation (see on unit square)

In Bilinear interpolation (like multi-linear interpolation) interpolated values for the vertices are exact.
There should be some crossed term xweight*yweight ...