最近由于项目需要，要在不缩小的情况下显示一张2500*2000大小的图片，找到了一篇博客写的非常好，是邹老师写于2011年的： http://blog.csdn.net/chenyusiyuan/article/details/6565424
我正在试着把它翻译成C 风格，用Mat类型，实现后会再发出来
原贴代码，简单修改并加上了一些注释，在VS2010上运行成功：
代码语言：javascript复制// Image_ScrollBar.cpp : Defines the entry point for the console application.
//
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc_c.h>
#include <iostream>
#include <vector>
using namespace std;
double mx = 0, my = 0;
int dx = 0, dy = 0, horizBar_x = 0, vertiBar_y = 0;
bool clickVertiBar = false, clickHorizBar = false, needScroll = false;
CvRect rect_bar_horiz, rect_bar_verti;
void help()
{
printf(
"/n"
"This program demonstrated the use of the cvSetMouseCallback /n"
"for viewing large image with scroll bar in a small window/n"
"created by OpenCV highgui model. (chenyusiyuan, 2011-06-24)/n"
"Call:/n"
"./Image_ScrollBar [<img_filename default im.jpg> <window_width default 1400> <window_height default 700>]/n/n"
);
}
void mouse_callback( int event, int x, int y, int flags, void* param )
{
if (needScroll)
{
switch( event )
{
case CV_EVENT_LBUTTONDOWN:
mx = x, my = y;
dx = 0, dy = 0;
// 按下左键时光标定位在水平滚动条区域内
if (x >= rect_bar_horiz.x && x <= rect_bar_horiz.x rect_bar_horiz.width
&& y >= rect_bar_horiz.y && y<= rect_bar_horiz.y rect_bar_horiz.height)
{
clickHorizBar = true;
}
// 按下左键时光标定位在垂直滚动条区域内
if (x >= rect_bar_verti.x && x <= rect_bar_verti.x rect_bar_verti.width
&& y >= rect_bar_verti.y && y<= rect_bar_verti.y rect_bar_verti.height)
{
clickVertiBar = true;
}
break;
case CV_EVENT_MOUSEMOVE:
if (clickHorizBar)
{
dx = fabs(x-mx) > 1 ? (int)(x-mx) : 0;
dy = 0;
}
if (clickVertiBar)
{
dx = 0;
dy = fabs(y-my) > 1 ? (int)(y-my) : 0;
}
mx = x, my = y;
break;
case CV_EVENT_LBUTTONUP:
mx = x, my = y;
dx = 0, dy = 0;
clickHorizBar = false;
clickVertiBar = false;
break;
default:
dx = 0, dy = 0;
break;
}
}
}
void myShowImageScroll(char* title, IplImage* src_img,
int winWidth = 1400, int winHeight = 700) // 显示窗口大小默认为 1400×700
{
IplImage* dst_img;
CvRect rect_dst, // 窗口中有效的图像显示区域
rect_src; // 窗口图像对应于源图像中的区域
int imgWidth = src_img->width,
imgHeight = src_img->height,
barWidth = 25; // 滚动条的宽度（像素）
double scale_w = (double)imgWidth/(double)winWidth, // 源图像与窗口的宽度比值 用以判断是否超出显示范围
scale_h = (double)imgHeight/(double)winHeight; // 源图像与窗口的高度比值 用以判断是否超出显示范围
if(scale_w<1) //如果小于1 说明原图比窗口小，窗口的宽度将重新赋值
winWidth = imgWidth barWidth;
if(scale_h<1) //如果小于1 说明原图比窗口小，窗口的高度将重新赋值
winHeight = imgHeight barWidth;
int showWidth = winWidth, showHeight = winHeight; // 窗口中有效的图像显示区域的宽和高
int src_x = 0, src_y = 0; // 源图像中 rect_src 的左上角位置
int horizBar_width = 0, horizBar_height = 0, //定义并初始化垂直于水平滑块的宽高
vertiBar_width = 0, vertiBar_height = 0;
needScroll = scale_w>1.0 || scale_h>1.0 ? true : false;
// 若图像大于设定的窗口大小，则显示滚动条
if(needScroll)
{
dst_img = cvCreateImage(cvSize(winWidth, winHeight),src_img->depth, src_img->nChannels);
cvZero(dst_img);
// 源图像宽度大于窗口宽度，则显示水平滚动条
if(scale_w > 1.0) //宽度超出了
{
showHeight = winHeight - barWidth;
horizBar_width = (int)((double)winWidth/scale_w);
horizBar_height = winHeight-showHeight;
horizBar_x = min(
max(0,horizBar_x dx),
winWidth-horizBar_width);
rect_bar_horiz = cvRect(
horizBar_x,
showHeight 1,
horizBar_width,
horizBar_height);
// 显示水平滚动条
cvRectangleR(dst_img, rect_bar_horiz, cvScalarAll(255), -1);
}
// 源图像高度大于窗口高度，则显示垂直滚动条
if(scale_h > 1.0) //高度超出了
{
showWidth = winWidth - barWidth;
vertiBar_width = winWidth-showWidth;
vertiBar_height = (int)((double)winHeight/scale_h);
vertiBar_y = min(
max(0,vertiBar_y dy),
winHeight-vertiBar_height);
rect_bar_verti = cvRect(
showWidth 1,
vertiBar_y,
vertiBar_width,
vertiBar_height); //确定垂直滚动条的白色部分的大小
// 显示垂直滚动条
cvRectangleR(dst_img, rect_bar_verti, cvScalarAll(255), -1);
}
showWidth = min(showWidth,imgWidth);
showHeight = min(showHeight,imgHeight);
// 设置窗口显示区的 ROI
rect_dst = cvRect(0, 0, showWidth, showHeight);
cvSetImageROI(dst_img, rect_dst);
// 设置源图像的 ROI
src_x = (int)((double)horizBar_x*scale_w);
src_y = (int)((double)vertiBar_y*scale_h);
src_x = min(src_x, imgWidth-showWidth);
src_y = min(src_y, imgHeight-showHeight);
rect_src = cvRect(src_x, src_y, showWidth, showHeight);
cvSetImageROI(src_img, rect_src);
// 将源图像内容复制到窗口显示区
cvCopy(src_img, dst_img);
cvResetImageROI(dst_img);
cvResetImageROI(src_img);
// 显示图像和滚动条
cvShowImage(title,dst_img);
cvReleaseImage(&dst_img);
}
// 源图像小于设定窗口，则直接显示图像，无滚动条
else
{
cvShowImage(title, src_img);
}
}
int main(int argc, char** argv)
{
help();
const char* filename = argc > 1 ? argv[1] : "1.bmp";
int width = 1200, height = 800;
if (4==argc)
{
sscanf( argv[2], "%u", &width );
sscanf( argv[3], "%u", &height );
}
cvNamedWindow("Image Scroll Bar", 1);
cvSetMouseCallback("Image Scroll Bar", mouse_callback);
IplImage* image = cvLoadImage( filename, CV_LOAD_IMAGE_COLOR );
if( !image )
{
fprintf( stderr, "Can not load %s and/or %s/n"
"Usage: Image_ScrollBar [<img_filename default im.jpg>]/n",
filename );
exit(-1);
}
while(1)
{
myShowImageScroll("Image Scroll Bar", image, width, height);
int KEY = cvWaitKey(10);
if( (char) KEY == 27 )
break;
}
cvDestroyWindow("Image Scroll Bar");
return 0;
} 
