Mat 和 CvMat，IplImage相互转化

The section is just a summary “cheatsheet” of common things you may want to do with cv::Mat:. The code snippets below all assume the correct

namespace is used:

using

 namespace

 cv

;




using

 namespace

 std

;

Convert an IplImage or CvMat to an cv::Mat and a cv::Mat to an IplImage or CvMat:

// Assuming somewhere IplImage *iplimg; exists




// and has been allocated and cv::Mat Mimg has been defined




Mat

 imgMat

(

iplimg

);

  //Construct an Mat image "img" out of an IplImage




Mimg

 =

 iplimg

;

       //Or just set the header of pre existing cv::Mat




                     //Ming to iplimg's data (no copying is done)







//Convert to IplImage or CvMat, no data copying




IplImage

 ipl_img

 =

 img

;




CvMat

 cvmat

 =

 img

;

 // convert cv::Mat -> CvMat

A very simple way to operate on a rectanglular sub-region of an image (ROI – “Region of Interest”):

//Make a rectangle




Rect

 roi

(

10

,

 20

,

 100

,

 50

);




//Point a cv::Mat header at it (no allocation is done)




Mat

 image_roi

 =

 image

(

roi

);

A bit advanced, but should you want efficiently to sample from a circular region in an image (below, instead of sampling, we just draw into a BGR image) :

// the function returns x boundary coordinates of




// the circle for each y. RxV[y1] = x1 means that




// when y=y1, -x1 <=x<=x1 is inside the circle




void

 getCircularROI

(

int

 R

,

 vector

 <

 int

 >

 &

 RxV

)




{




    RxV

.

resize

(

R

+

1

);




    for

(

 int

 y

 =

 0

;

 y

 <=

 R

;

 y

++

 )




        RxV

[

y

]

 =

 cvRound

(

sqrt

((

double

)

R

*

R

 -

 y

*

y

));




}







// This draws a circle in the green channel




// (note the "[1]" for a BGR" image,




// blue and red channels are not modified),




// but is really an example of how to *sample* from a circular region.




void

 drawCircle

(

Mat

 &

image

,

 int

 R

,

 Point

 center

)




{




    vector

<

int

>

 RxV

;




    getCircularROI

(

R

,

 RxV

);







    Mat_

<

Vec3b

>&

 img

 =

 (

Mat_

<

Vec3b

>&

)

image

;

 //3 channel pointer to image




    for

(

 int

 dy

 =

 -

R

;

 dy

 <=

 R

;

 dy

++

 )




    {




        int

 Rx

 =

 RxV

[

abs

(

dy

)];




        for

(

 int

 dx

 =

 -

Rx

;

 dx

 <=

 Rx

;

 dx

++

 )




            img

(

center

.

y

+

dy

,

 center

.

x

+

dx

)[

1

]

 =

 255

;




    }




}




出自：http://opencv.willowgarage.com/documentation/cpp/c++_cheatsheet.html