使用Opencv_CUDA 实现访问图像像素、直方图均衡化、几何变换

• 访问图像的各个像素强度
• 直方图的计算与均衡
• 几何变换：缩放、平移与旋转

1. 访问图像的各个像素强度

#include <iostream>
#include "opencv2/opencv.hpp"


int main()
{
	cv::Mat h_img1 = cv::imread("images/cameraman.tif", 0);
	cv::Scalar intensity = h_img1.at<uchar>(cv::Point(100, 50));
	std::cout << "Pixel Intensity of gray scale Image at (100,50) is:" << intensity.val[0] << std::endl;
	cv::Mat h_img2 = cv::imread("images/autumn.tif", 1);
	cv::Vec3b intensity1 = h_img2.at<cv::Vec3b>(cv::Point(100, 50));
	std::cout << "Pixel Intensity of color Image at (100,50) is:" << intensity1 << std::endl;
	return 0;
}

2. 直方图计算与均衡

• 直方图时图像的一个非常重要的属性，提供了图像外观的全局描述
• 通常直方图均匀分布，可以得到较好的视觉效果
• 对灰度图实现均衡化：

#include <iostream>
#include "opencv2/opencv.hpp"
#include<cudaimgproc.hpp>


int main()
{
    cv::Mat h_img1 = cv::imread("images/cameraman.tif", 0);
    cv::cuda::GpuMat d_img1, d_result1;
    d_img1.upload(h_img1);
    cv::cuda::equalizeHist(d_img1, d_result1);
    cv::Mat h_result1;
    d_result1.download(h_result1);
    cv::imshow("Original Image ", h_img1);
    cv::imshow("Histogram Equalized Image", h_result1);
    cv::imwrite("images/result_inversion.png", h_img1);
    cv::imwrite("images/result_inversion.png", h_result1);
    cv::waitKey();
    return 0;
}

• 对三通道彩色图实现均衡化：

#include <iostream>
#include "opencv2/opencv.hpp"


int main()
{
    cv::Mat h_img1 = cv::imread("images/autumn.tif");
    cv::Mat h_img2, h_result1;
    cvtColor(h_img1, h_img2, cv::COLOR_BGR2HSV);
    //Split the image into 3 channels; H, S and V channels respectively and store it in a std::vector
    std::vector< cv::Mat > vec_channels;
    cv::split(h_img2, vec_channels);
    //Equalize the histogram of only the V channel 
    cv::equalizeHist(vec_channels[2], vec_channels[2]);
    //Merge 3 channels in the vector to form the color image in HSV color space.
    cv::merge(vec_channels, h_img2);

    //Convert the histogram equalized image from HSV to BGR color space again
    cv::cvtColor(h_img2, h_result1, cv::COLOR_HSV2BGR);
    cv::imshow("Original Image ", h_img1);
    cv::imshow("Histogram Equalized Image", h_result1);
    cv::waitKey();
    return 0;
}

3. 几何变换

• 图像缩放：

#include <iostream>
#include "opencv2/opencv.hpp"
#include<opencv2/cudawarping.hpp>

int main()
{
    cv::Mat h_img1 = cv::imread("images/cameraman.tif", 0);
    cv::cuda::GpuMat d_img1, d_result1, d_result2;
    d_img1.upload(h_img1);
    int width = d_img1.cols;
    int height = d_img1.size().height;
    cv::cuda::resize(d_img1, d_result1, cv::Size(200, 200), cv::INTER_CUBIC);
    cv::cuda::resize(d_img1, d_result2, cv::Size(0.5 * width, 0.5 * height), cv::INTER_LINEAR);
    cv::Mat h_result1, h_result2;
    d_result1.download(h_result1);
    d_result2.download(h_result2);
    cv::imshow("Original Image ", h_img1);
    cv::imshow("Resized Image", h_result1);
    cv::imshow("Resized Image 2", h_result2);
    cv::imwrite("Resized1.png", h_result1);
    cv::imwrite("Resized2.png", h_result2);
    cv::waitKey();
    return 0;
}

• 图像平移与旋转

#include <iostream>
#include "opencv2/opencv.hpp"
#include<opencv2/cudawarping.hpp>

int main()
{
	cv::Mat h_img1 = cv::imread("images/cameraman.tif", 0);
	cv::cuda::GpuMat d_img1, d_result1, d_result2;
	d_img1.upload(h_img1);
	int cols = d_img1.cols;
	int rows = d_img1.size().height;
	//Translation
	cv::Mat trans_mat = (cv::Mat_<double>(2, 3) << 1, 0, 70, 0, 1, 50);
	cv::cuda::warpAffine(d_img1, d_result1, trans_mat, d_img1.size());
	//Rotation
	cv::Point2f pt(d_img1.cols / 2., d_img1.rows / 2.);
	cv::Mat r = cv::getRotationMatrix2D(pt, 45, 1.0);
	cv::cuda::warpAffine(d_img1, d_result2, r, cv::Size(d_img1.cols, d_img1.rows));
	cv::Mat h_result1, h_result2;
	d_result1.download(h_result1);
	d_result2.download(h_result2);
	cv::imshow("Original Image ", h_img1);
	cv::imshow("Translated Image", h_result1);
	cv::imshow("Rotated Image", h_result2);
	cv::imwrite("Translated.png", h_result1);
	cv::imwrite("Rotated.png", h_result2);
	cv::waitKey();
	return 0;
}