基于OpenCV给图片添加边框

目标：

基于OpenCV的函数cv::copyMakeBorder给图像添加边框

函数简介：

copyMakeBorder( src, dst, top, bottom, left, right, borderType, value );

参数:

1. src: 原图像
2. dst: 目标图像
3. top, bottom, left, right: 每一个边界方向上像素的宽度.在这里使用图像原始大小的 5% .
4. borderType:边框的类型 。当前例子中位纯色或者边界的复制.
5. value: 如果borderType 设置位 BORDER_CONSTANT, 这个将作为边框的颜色.

边框的类型

1）纯色边框

    BORDER_CONSTANT，边框设置位某种单一的颜色，比如黑色

2）图像边界扩展

BORDER_REPLICATE，复制原图的边界进行扩展

代码

/**
 * @file copyMakeBorder_demo.cpp
 * @brief Sample code that shows the functionality of copyMakeBorder
 * @author OpenCV team
 */

#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

//![variables]
Mat src, dst;
int top, bottom, left, right;
int borderType;
const char* window_name = "copyMakeBorder Demo";
RNG rng(12345);
//![variables]

/**
 * @function main
 */
int main( int, char** argv )
{

  int c;

  //![load]
  src = imread( argv[1], IMREAD_COLOR ); // Load an image

  if( src.empty() )
    {
      printf(" No data entered, please enter the path to an image file \n");
      return -1;
    }
  //![load]

  /// Brief how-to for this program
  printf( "\n \t copyMakeBorder Demo: \n" );
  printf( "\t -------------------- \n" );
  printf( " ** Press 'c' to set the border to a random constant value \n");
  printf( " ** Press 'r' to set the border to be replicated \n");
  printf( " ** Press 'ESC' to exit the program \n");

  //![create_window]
  namedWindow( window_name, WINDOW_AUTOSIZE );
  //![create_window]

  //![init_arguments]
  /// Initialize arguments for the filter
  top = (int) (0.05*src.rows); bottom = (int) (0.05*src.rows);
  left = (int) (0.05*src.cols); right = (int) (0.05*src.cols);
  //![init_arguments]

  dst = src;
  imshow( window_name, dst );

  for(;;)
       {
         //![check_keypress]
         c = waitKey(500);

         if( (char)c == 27 )
           { break; }
         else if( (char)c == 'c' )
           { borderType = BORDER_CONSTANT; }
         else if( (char)c == 'r' )
           { borderType = BORDER_REPLICATE; }
         //![check_keypress]

         //![update_value]
         Scalar value( rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255) );
         //![update_value]

         //![copymakeborder]
         copyMakeBorder( src, dst, top, bottom, left, right, borderType, value );
         //![copymakeborder]

         //![display]
         imshow( window_name, dst );
         //![display]
       }

  return 0;
}

效果