From 44e38781d1188cbcac2409f398cb610b39d774b4 Mon Sep 17 00:00:00 2001
From: bsdnoobz <nash@bsd-noobz.com>
Date: Thu, 7 Feb 2013 11:36:48 +0700
Subject: Added straighten-img.cpp

---
 straighten-img.cpp | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 straighten-img.cpp

diff --git a/straighten-img.cpp b/straighten-img.cpp
new file mode 100644
index 0000000..102e8e5
--- /dev/null
+++ b/straighten-img.cpp
@@ -0,0 +1,83 @@
+/*
+straighten-img.cpp
+Draw a line on an image and the image rotates so that the line is horizontal
+
+Author:  Nash 
+Website: http://opencv-code.com/tutorials/straighten-up-an-image/
+
+Usage:
+1. Click to set the start point.
+2. Drag your mouse.
+3. Click to set the end point.
+4. The corrected image will be displayed.
+5. Click the original image again to restart.
+6. Press 'q' to quit.
+*/
+
+#include <opencv2/imgproc/imgproc.hpp>
+#include <opencv2/highgui/highgui.hpp>
+#include <cmath>
+#include <iostream>
+
+cv::Mat im0, im1;
+std::vector<cv::Point> pt;
+
+void straighten_image(std::vector<cv::Point> pt)
+{
+	double angle = std::atan((double)(pt[0].y - pt[1].y) / 
+	                                 (pt[0].x - pt[1].x)) * 
+	                                 (180 / CV_PI);
+
+	cv::Point2f center(im0.cols/2., im0.rows/2.);
+	cv::Mat dst, r = cv::getRotationMatrix2D(center, angle, 1.0);
+	cv::warpAffine(im0, dst, r, im0.size());
+	cv::imshow("dst", dst);
+	cv::imwrite("src.jpg", im1);
+	cv::imwrite("dst.jpg", dst);
+}
+
+void on_mouse(int event, int x, int y, int flags, void* param)
+{
+	if (event == CV_EVENT_LBUTTONDOWN)
+	{
+		switch (pt.size())
+		{
+			case 0:
+				pt.push_back(cv::Point(x,y));
+				break;
+			case 1:
+				pt.push_back(cv::Point(x,y));
+				straighten_image(pt);
+				break;
+			case 2:
+				im1 = im0.clone();
+				pt.clear();
+				break;
+		}
+	}
+	else if (event == CV_EVENT_MOUSEMOVE && pt.size() == 1)
+	{
+		im1 = im0.clone();
+		cv::line(im1, pt[0], cv::Point(x,y), CV_RGB(255,0,0), 2);
+	}
+
+	if (im1.data)
+		cv::imshow("src", im1);
+}
+
+int main()
+{
+	im0 = cv::imread("lena.png");
+	if (!im0.data)
+	{
+		std::cout << "Cannot load source image!" << std::endl;
+		return -1;
+	}
+
+	cv::namedWindow("src", CV_WINDOW_AUTOSIZE);
+	cv::setMouseCallback("src", on_mouse, 0);
+	cv::imshow("src", im0);
+	cv::waitKey();
+	return 0;
+}
+
-- 
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