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