opencv3 图像处理（一）图像缩放（ python与c++ 实现）

opencv3 图像处理 之 图像缩放（ python与c++实现 ）

一. 主要函数介绍

1) 图像大小变换 Resize ()

原型：

void Resize(const CvArr* src,CvArr* dst,intinterpolation=CV_INTER_LINEAR);

说明：

2）图像读取 imread（）

原型：

python:
cv2.imread(filename[, flags]) → retval
c++:
Mat imread(const string& filename, int flags=1 )

说明：

3)图像创建 imwrite（）

原型：

python:
cv2.imwrite(filename, image[, params])
c++:
bool imwrite(const string& filename, InputArray image, const vector<int>& params=vector<int>())

说明：

注意： C++ 中 imwrite（函数的） params参数 ：

二、实例

python版（python3.5 opencv3.4）：

import numpy as np
import cv2

def resizeImage(image,width=None,height=None,inter=cv2.INTER_AREA):
newsize = (width,height)
#获取图像尺寸
(h,w) = image.shape[:2]
if width is None and height is None:
return image
#高度算缩放比例
if width is None:
n = height/float(h)
newsize = (int(n*w),height)
else :
n = width/float(w)
newsize = (width,int(h*n))

# 缩放图像
newimage = cv2.resize(image, newsize, interpolation=inter)
return newimage

imageOriginal = cv2.imread("test.jpg")
cv2.imshow("Original", imageOriginal)
#获取图像尺寸
w = width=imageOriginal.shape[1]
h = width=imageOriginal.shape[2]
print ("Image size:",w,h)
#放大2倍
newimage = resizeImage(imageOriginal,w*2,h*2,cv2.INTER_LINEAR)
cv2.imshow("New", newimage)
#保存缩放后的图像
cv2.imwrite('newimage.jpg',newimage)
#缩小5倍
newimage2 = resizeImage(imageOriginal,int(w/5),int(h/5),cv2.INTER_LINEAR)
cv2.imwrite('newimage2.jpg',newimage2)

C++ 版(imageResize.cpp)

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

using namespace std;
using namespace cv;

void imageResize(Mat image, Mat* dst, int width, int height, int inter = CV_INTER_AREA )
{

int w = image.cols;
int h = image.rows;
int newW = width;
int newH = height;
if(width == 0 && height ==0){
return;
}
if(width == 0){
float re = h/(float)height;
newW = (int) w * re;
} else {
float re = w/(float)width;
newH = (int) h * re;;
}

resize(image, *dst, Size(newW, newH),inter);

}

int main()
{
const char* filename = "test.jpg";
Mat image,dst;
//image = imread(filename, CV_LOAD_IMAGE_GRAYSCALE);
image = imread(filename, CV_LOAD_IMAGE_COLOR);
if (image.empty()) {
std::cout<<"Faild open file.";
}
//imshow("image", image);
//image.cols为图像的宽度 image.cols为图像的高度
int w = image.cols;
int h = image.rows;
std::cout<<"Image size:"<<w <<" * "<<h<<std::endl;
imageResize(image,&dst,w * 2, h * 2);

std::cout<<"new Image size:"<<dst.cols <<" * "<<dst.rows<<std::endl;
vector<int> compression_params;
//JPEG，参数为CV_IMWRITE_JPEG_QUALITY，值是从0到100，值越小压缩的越多
compression_params.push_back(CV_IMWRITE_JPEG_QUALITY);
compression_params.push_back(100);
//imshow("dstImage", dst);
imwrite("dstImage.jpg",dst,compression_params);

return 0;
}

编译：

sudo g++ imageResize.cpp  -o resize  `pkg-config --cflags --libs opencv