- 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