[转]OpenCV: 分配与释放图像空间

心已赠人 2022-08-04 13:58 184阅读 0赞

经典中的经典, 真乃美味也!

分配与释放图像空间

分配图像空间:  
IplImage\* cvCreateImage(CvSize size, int depth, int channels);

size: cvSize(width,height);

depth: IPL\_DEPTH\_8U, IPL\_DEPTH\_8S, IPL\_DEPTH\_16U,  
IPL\_DEPTH\_16S, IPL\_DEPTH\_32S, IPL\_DEPTH\_32F, IPL\_DEPTH\_64F

channels: 1, 2, 3 or 4.  
注意数据为交叉存取.彩色图像的数据编排为b0 g0 r0 b1 g1 r1 ...

举例:

// 分配一个单通道字节图像  
IplImage\* img1=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);

// 分配一个三通道浮点图像  
IplImage\* img2=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_32F,3);

释放图像空间:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
cvReleaseImage(&img);

复制图像:  
IplImage\* img1=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
IplImage\* img2;  
img2=cvCloneImage(img1);

设定/获取兴趣区域:  
void cvSetImageROI(IplImage\* image, CvRect rect);  
void cvResetImageROI(IplImage\* image);  
vRect cvGetImageROI(const IplImage\* image);

大部分OpenCV函数都支持ROI.

设定/获取兴趣通道:  
void cvSetImageCOI(IplImage\* image, int coi); // 0=all  
int cvGetImageCOI(const IplImage\* image);

大部分OpenCV函数暂不支持COI.

读取存储图像

从文件中载入图像:  
IplImage\* img=0;  
img=cvLoadImage(fileName);  
if(!img) printf("Could not load image file: %s/n",fileName);

Supported image formats: BMP, DIB, JPEG, JPG, JPE, PNG, PBM, PGM, PPM,  
SR, RAS, TIFF, TIF

载入图像默认转为3通道彩色图像. 如果不是，则需加flag:

img=cvLoadImage(fileName,flag);

flag: >0 载入图像转为三通道彩色图像  
=0 载入图像转为单通道灰度图像  
<0 不转换载入图像(通道数与图像文件相同).

图像存储为图像文件:  
if(!cvSaveImage(outFileName,img)) printf("Could not save: %s/n",outFileName);

输入文件格式由文件扩展名决定.

存取图像元素

假设需要读取在i行j列像点的第k通道. 其中, 行数i的范围为\[0, height-1\], 列数j的范围为\[0, width-1\], 通道k的范围为\[0, nchannels-1\].  
间接存取: (比较通用, 但效率低, 可读取任一类型图像数据)  
对单通道字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
CvScalar s;  
s=cvGet2D(img,i,j); // get the (i,j) pixel value  
printf("intensity=%f/n",s.val\[0\]);  
s.val\[0\]=111;  
cvSet2D(img,i,j,s); // set the (i,j) pixel value

对多通道浮点或字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_32F,3);  
CvScalar s;  
s=cvGet2D(img,i,j); // get the (i,j) pixel value  
printf("B=%f, G=%f, R=%f/n",s.val\[0\],s.val\[1\],s.val\[2\]);  
s.val\[0\]=111;  
s.val\[1\]=111;  
s.val\[2\]=111;  
cvSet2D(img,i,j,s); // set the (i,j) pixel value

直接存取: (效率高, 但容易出错)  
对单通道字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
((uchar \*)(img->imageData + i\*img->widthStep))\[j\]=111;

对多通道字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,3);  
((uchar \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 0\]=111; // B  
((uchar \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 1\]=112; // G  
((uchar \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 2\]=113; // R

对多通道浮点图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_32F,3);  
((float \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 0\]=111; // B  
((float \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 1\]=112; // G  
((float \*)(img->imageData + i\*img->widthStep))\[j\*img->nChannels + 2\]=113; // R

用指针直接存取 : (在某些情况下简单高效)  
对单通道字节图像:  
IplImage\* img = cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
int height = img->height;  
int width = img->width;  
int step = img->widthStep/sizeof(uchar);  
uchar\* data = (uchar \*)img->imageData;  
data\[i\*step+j\] = 111;

对多通道字节图像:  
IplImage\* img = cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,3);  
int height = img->height;  
int width = img->width;  
int step = img->widthStep/sizeof(uchar);  
int channels = img->nChannels;  
uchar\* data = (uchar \*)img->imageData;  
data\[i\*step+j\*channels+k\] = 111;

对单通道浮点图像(假设用4字节调整):  
IplImage\* img = cvCreateImage(cvSize(640,480),IPL\_DEPTH\_32F,3);  
int height = img->height;  
int width = img->width;  
int step = img->widthStep/sizeof(float);  
int channels = img->nChannels;  
float \* data = (float \*)img->imageData;  
data\[i\*step+j\*channels+k\] = 111;

使用 c++ wrapper 进行直接存取: (简单高效)  
对单/多通道字节图像，多通道浮点图像定义一个 c++ wrapper:  
template<class T> class Image  
\{  
private:  
IplImage\* imgp;  
public:  
Image(IplImage\* img=0) \{imgp=img;\}  
~Image()\{imgp=0;\}  
void operator=(IplImage\* img) \{imgp=img;\}  
inline T\* operator\[\](const int rowIndx) \{  
return ((T \*)(imgp->imageData + rowIndx\*imgp->widthStep));\}  
\};

typedef struct\{  
unsigned char b,g,r;  
\} RgbPixel;

typedef struct\{  
float b,g,r;  
\} RgbPixelFloat;

typedef Image<RgbPixel> RgbImage;  
typedef Image<RgbPixelFloat> RgbImageFloat;  
typedef Image<unsigned char> BwImage;  
typedef Image<float> BwImageFloat;

单通道字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,1);  
BwImage imgA(img);  
imgA\[i\]\[j\] = 111;

多通道字节图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_8U,3);  
RgbImage imgA(img);  
imgA\[i\]\[j\].b = 111;  
imgA\[i\]\[j\].g = 111;  
imgA\[i\]\[j\].r = 111;

多通道浮点图像:  
IplImage\* img=cvCreateImage(cvSize(640,480),IPL\_DEPTH\_32F,3);  
RgbImageFloat imgA(img);  
imgA\[i\]\[j\].b = 111;  
imgA\[i\]\[j\].g = 111;  
imgA\[i\]\[j\].r = 111;

图像转换

转为灰度或彩色字节图像:  
cvConvertImage(src, dst, flags=0);

src = float/byte grayscale/color image  
dst = byte grayscale/color image  
flags = CV\_CVTIMG\_FLIP (flip vertically)  
CV\_CVTIMG\_SWAP\_RB (swap the R and B channels)

转换彩色图像为灰度图像:

使用OpenCV转换函数:

cvCvtColor(cimg,gimg,CV\_BGR2GRAY); // cimg -> gimg

直接转换:

for(i=0;i<cimg->height;i++) for(j=0;j<cimg->width;j++)  
gimgA\[i\]\[j\]= (uchar)(cimgA\[i\]\[j\].b\*0.114 +  
cimgA\[i\]\[j\].g\*0.587 +  
cimgA\[i\]\[j\].r\*0.299);

颜色空间转换:  
cvCvtColor(src,dst,code); // src -> dst

code = CV\_<X>2<Y>  
<X>/<Y> = RGB, BGR, GRAY, HSV, YCrCb, XYZ, Lab, Luv, HLS

e.g.: CV\_BGR2GRAY, CV\_BGR2HSV, CV\_BGR2Lab

绘图命令

画长方体:  
// 用宽度为1的红线在(100,100)与(200,200)之间画一长方体  
cvRectangle(img, cvPoint(100,100), cvPoint(200,200), cvScalar(255,0,0), 1);

画圆:  
// 在(100,100)处画一半径为20的圆,使用宽度为1的绿线  
cvCircle(img, cvPoint(100,100), 20, cvScalar(0,255,0), 1);

画线段:  
// 在(100,100)与(200,200)之间画绿色线段，宽度为1  
cvLine(img, cvPoint(100,100), cvPoint(200,200), cvScalar(0,255,0), 1);

画一组线段:  
CvPoint curve1\[\]=\{10,10, 10,100, 100,100, 100,10\};  
CvPoint curve2\[\]=\{30,30, 30,130, 130,130, 130,30, 150,10\};  
CvPoint\* curveArr\[2\]=\{curve1, curve2\};  
int nCurvePts\[2\]=\{4,5\};  
int nCurves=2;  
int isCurveClosed=1;  
int lineWidth=1;

cvPolyLine(img,curveArr,nCurvePts,nCurves,isCurveClosed,cvScalar(0,255,255),lineWidth);

画内填充色的多边形:  
cvFillPoly(img,curveArr,nCurvePts,nCurves,cvScalar(0,255,255));

添加文本:  
CvFont font;  
double hScale=1.0;  
double vScale=1.0;  
int lineWidth=1;  
cvInitFont(&font,CV\_FONT\_HERSHEY\_SIMPLEX|CV\_FONT\_ITALIC, hScale,vScale,0,lineWidth);

cvPutText (img,"My comment",cvPoint(200,400), &font, cvScalar(255,255,0));

Other possible fonts:

CV\_FONT\_HERSHEY\_SIMPLEX, CV\_FONT\_HERSHEY\_PLAIN,  
CV\_FONT\_HERSHEY\_DUPLEX, CV\_FONT\_HERSHEY\_COMPLEX,  
CV\_FONT\_HERSHEY\_TRIPLEX, CV\_FONT\_HERSHEY\_COMPLEX\_SMALL,  
CV\_FONT\_HERSHEY\_SCRIPT\_SIMPLEX, CV\_FONT\_HERSHEY\_SCRIPT\_COMPLEX,

本文来自CSDN博客，转载请标明出处：[http://blog.csdn.net/zhenxiaohui/archive/2009/08/03/4405177.aspx][http_blog.csdn.net_zhenxiaohui_archive_2009_08_03_4405177.aspx]

[http_blog.csdn.net_zhenxiaohui_archive_2009_08_03_4405177.aspx]: http://blog.csdn.net/zhenxiaohui/archive/2009/08/03/4405177.aspx