[OpenCV笔记]0.OpenCV中显示多张图像
摘要
本文主要介绍OpenCV中同时显示多张IplImage图像的方法(C++形式的多图显示需要修改，用vector<Mat>可能比较方便)，有点类似MATLAB中的subplot，只是暂时还没有subplot那么完善，这种方法主要思想和用到的技术为：
- 主要思想：将多张小图组合成一张大图来显示
- 组合方式：按照图片的数量，将大图分割成特定的行列数，每一个小块放一张子图
- 输入方式：使用 中的 type va_list ，就可定义形参数目不确定的函数了。
1. va_list
- va_start Initialize a variable argument list (macro ) 初始化可变参数列
- va_arg Retrieve next argument (macro ) 读取下一个参数
- va_end End using variable argument list (macro ) 结束可变参数列的使用
下面是va_list的一个应用例子：
void PrintFloats (int n, ...)
{
int i;
double val;
printf ("Printing floats:");
va_list vl;
va_start(vl,n);
for (i=0;i<n;i++)
{
val=va_arg(vl,double);
printf (" [%.2f]",val);
}
va_end(vl);
printf ("\n");
}
2. cvShowMultiImages
程序需要的头文件：
#include <stdio.h> // printf #include <stdarg.h> // va_list, va_start, va_arg, va_end #include "cv.h" #include "opencv2/highgui/highgui_c.h"
主体程序：
void cvShowMultiImages(char* title,int nChannels, int nArgs, ...)
{
IplImage* img; // img - Used for getting the arguments
IplImage* DispImage;// DispImage - the image in which all the input images are to be copied
int size_r,size_c; // size - the size of the images in the window
int ind; // ind - the index of the image shown in the window
int x_c, y_r; // x_c,y_r - the coordinate of top left coner of input images
int w, h; // w,h - the width and height of the image
int r, c; // r - row , c - col
int space_r,space_c;// space - the spacing between images
if(nArgs <= 0) { // If argc < 0 or argc > 12 , return without displaying
printf("Number of arguments too small..../n");
return;
}
else if(nArgs > 12) {
printf("Number of arguments too large..../n");
return;
}
// Determine the size of the image,
// and the number of rows/cols
// from number of arguments
else if (nArgs == 1) {
r = c = 1;
size_r = 480; size_c = 640 ;
}
else if (nArgs == 2) { // x_c = size_row y_r=size_col
r = 1; c = 2;
// size_r = 705; size_c = 350 ; // specail set for show the full story of lena
size_r = 405; size_c = 540 ;
}
else if ( nArgs == 3 || nArgs == 4) {
r = 2; c = 2;
size_r = 405; size_c =540 ;
}
else if (nArgs == 5 || nArgs == 6) {
r = 2; c = 3;
size_r = 360; size_c = 480;
}
else if (nArgs == 7 || nArgs == 8) {
r = 2; c = 4;
size_r = 200; size_c = 240;
}
else {
r = 3; c = 4;
size_r = 150; size_c = 200;
}
// Create a new 3 channel image to show all the input images
// cvSize(width,height)=(col,row)=(y_r,x_c)
DispImage = cvCreateImage( cvSize(30 + size_c*c,40 + size_r*r), IPL_DEPTH_8U, nChannels );
// Used to get the arguments passed
va_list args;
va_start(args, nArgs); // stdarg.h
// Loop for nArgs number of arguments
space_r = 40/(r+1);
space_c = 30/(c+1);
for (ind = 0, x_c = space_c, y_r = space_r; ind < nArgs; ind++, x_c += (space_c + size_c)) {
// Get the Pointer to the IplImage
img = va_arg(args, IplImage*); // stdarg.h
if(img == 0) {// If img == NULL, release the image, and return
printf("Invalid arguments");
cvReleaseImage(&DispImage);
return;
}
// Find the width and height of the image
w = img->width;
h = img->height;
// Used to Align the images
// i.e. Align the image to next row e.g.r=1,c=2, this row is end , we have ind%c==0 ,
// then we move to the next row,even the next row can't through the cond ind < nArgs
if( ind % c == 0 && x_c!= space_c) {
x_c = space_c;
y_r += space_r + size_r;
}
cvSetImageROI(DispImage, cvRect(x_c, y_r, size_c, size_r)); // Set the image ROI to display the current image
cvResize(img, DispImage); // Resize the input image and copy the it to the Single Big Image
cvResetImageROI(DispImage); // Reset the ROI in order to display the next image
}
cvNamedWindow( title, 1 ); // Create a new window, and show the Single Big Image
cvShowImage( title, DispImage);
cvWaitKey(0);
va_end(args); // End the number of arguments
cvReleaseImage(&DispImage); // Release the Image Memory
}
3. 程序调用方式与结果显示
应用时，请注意所有输入的图像都应该为同一个通道数：1或者3
cvShowMultiImages("Lena1",3,2,src1,edges1Color);
cvShowMultiImages("Lena2",3,2,src2,edges2Color);
显示结果为：
好吧，其实me更想展示的是 ———— The Complete Story of Lena ：
