add exact bilinearResize

src/matutils.cpp

@@ -351,3 +351,62 @@ void removeEmptyFrontBackCols(cv::Mat& mat)
 	if(frontRej || backRej) removeEmptyFrontBackCols(mat);
 }
 
+
+static float linInterpolate(float A, float B, float x)
+{
+	return A * (1.0f - x) + B * x;
+}
+
+template <typename Type> static Type resizePointBilinear(const cv::Mat& inImage, float scaledX, float scaledY, 
+														 float xFrac, float yFrac)
+{
+	int u0 = static_cast<int>(scaledX);
+	int v0 = static_cast<int>(scaledY);
+	int u1 = std::min(inImage.cols-1, static_cast<int>(scaledX+1));
+	int v1 = v0;
+	int u2 = u0;
+	int v2 = std::min(inImage.rows-1, static_cast<int>(scaledY+1));
+	int u3 = std::min(inImage.cols-1, static_cast<int>(scaledX+1));
+	int v3 = std::min(inImage.rows-1, static_cast<int>(scaledY+1));
+
+	float col0 = linInterpolate(inImage.at<Type>(v0, u0), inImage.at<Type>(v1, u1), xFrac);
+	float col1 = linInterpolate(inImage.at<Type>(v2, u2), inImage.at<Type>(v3, u3), xFrac);
+	float value = linInterpolate(col0, col1, yFrac);
+
+	return cv::saturate_cast<Type>(value);
+}
+
+template <typename Type> static void resize(const cv::Mat& inImage, cv::Mat& outImage) 
+{
+	float scaleY = (inImage.rows - 1) / static_cast<float>(outImage.rows - 1);
+	float scaleX = (inImage.cols - 1) / static_cast<float>(outImage.cols - 1);
+
+	for (int y = 0; y < outImage.rows; ++y) 
+	{
+		float scaledY = y * scaleY;
+		float yFrac = scaledY - static_cast<int>(scaledY);
+
+		for (int x = 0; x < outImage.cols; x++)
+		{
+			float scaledX = x * scaleX;
+			float xFrac = scaledX - static_cast<int>(scaledX);
+
+			outImage.at<Type>(y, x) = resizePointBilinear<Type>(inImage, scaledX, scaledY, xFrac, yFrac);
+		}
+	}
+}
+
+bool bilinearResize(const cv::Mat& inImage, cv::Mat& outImage, const cv::Size size) 
+{
+	if (!(inImage.type() == CV_8U || inImage.type() == CV_32F) ||
+	size.width < 2 || size.height < 2 || inImage.cols < 2 || inImage.rows < 2)
+		return false;
+
+	outImage = cv::Mat::zeros(size.height, size.width, inImage.type());
+
+	if(inImage.type() == CV_8U)
+		resize<uint8_t>(inImage, outImage);
+	else if(inImage.type() == CV_32F)
+		resize<float>(inImage, outImage);
+	return true;
+}

src/matutils.h

@@ -47,4 +47,7 @@ bool deleteEmptyCols(cv::Mat& mat);
 
 void removeEmptyFrontBackCols(cv::Mat& mat);
 
+bool bilinearResize(const cv::Mat& inImage, cv::Mat& outImage, cv::Size size);
+
+