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OpenCV
3.2.0
Open Source Computer Vision
|
.2.0+dfsg_doc_tutorials_imgproc_shapedescriptors_moments_moments
Goal
In this tutorial you will learn how to:
Theory
Code
This tutorial code's is shown lines below. You can also download it from here
#include <iostream>
using namespace std;
int thresh = 100;
int max_thresh = 255;
void thresh_callback(int, void* );
int main( int, char** argv )
{
const char* source_window = "Source";
createTrackbar(
" Canny thresh:",
"Source", &thresh, max_thresh, thresh_callback );
thresh_callback( 0, 0 );
return(0);
}
void thresh_callback(int, void* )
{
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
Canny( src_gray, canny_output, thresh, thresh*2, 3 );
vector<Moments> mu(contours.size() );
for(
size_t i = 0;
i < contours.size();
i++ )
vector<Point2f> mc( contours.size() );
for(
size_t i = 0;
i < contours.size();
i++ )
{ mc[
i] =
Point2f(
static_cast<float>(mu[
i].m10/mu[
i].m00) ,
static_cast<float>(mu[
i].m01/mu[
i].m00) ); }
for(
size_t i = 0;
i< contours.size();
i++ )
{
Scalar color =
Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
circle( drawing, mc[
i], 4, color, -1, 8, 0 );
}
imshow(
"Contours", drawing );
printf("\t Info: Area and Contour Length \n");
for(
size_t i = 0;
i< contours.size();
i++ )
{
printf(
" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f \n", (
int)
i, mu[
i].m00,
contourArea(contours[
i]),
arcLength( contours[
i],
true ) );
Scalar color =
Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
circle( drawing, mc[
i], 4, color, -1, 8, 0 );
}
}
Explanation
Result
Here it is:
@ IMREAD_COLOR
If set, always convert image to the 3 channel BGR color image.
Definition: imgcodecs.hpp:67
static MatExpr zeros(int rows, int cols, int type)
Returns a zero array of the specified size and type.
void cvtColor(InputArray src, OutputArray dst, int code, int dstCn=0)
Converts an image from one color space to another.
Point_< float > Point2f
Definition: types.hpp:181
int waitKey(int delay=0)
Waits for a pressed key.
void Canny(InputArray image, OutputArray edges, double threshold1, double threshold2, int apertureSize=3, bool L2gradient=false)
Finds edges in an image using the Canny algorithm .
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a window.
Size2i Size
Definition: types.hpp:315
Mat imread(const String &filename, int flags=IMREAD_COLOR)
Loads an image from a file.
@ COLOR_BGR2GRAY
convert between RGB/BGR and grayscale, color conversions
Definition: imgproc.hpp:538
#define CV_8UC3
Definition: interface.h:84
double contourArea(InputArray contour, bool oriented=false)
Calculates a contour area.
MatSize size
Definition: mat.hpp:1978
double arcLength(InputArray curve, bool closed)
Calculates a contour perimeter or a curve length.
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
Scalar_< double > Scalar
Definition: types.hpp:606
Random Number Generator.
Definition: core.hpp:2690
void drawContours(InputOutputArray image, InputArrayOfArrays contours, int contourIdx, const Scalar &color, int thickness=1, int lineType=LINE_8, InputArray hierarchy=noArray(), int maxLevel=INT_MAX, Point offset=Point())
Draws contours outlines or filled contours.
void blur(InputArray src, OutputArray dst, Size ksize, Point anchor=Point(-1,-1), int borderType=BORDER_DEFAULT)
Blurs an image using the normalized box filter.
Point2i Point
Definition: types.hpp:183
n-dimensional dense array class
Definition: mat.hpp:741
for i
Definition: modelConvert.m:63
int createTrackbar(const String &trackbarname, const String &winname, int *value, int count, TrackbarCallback onChange=0, void *userdata=0)
Creates a trackbar and attaches it to the specified window.
Definition: affine.hpp:52
@ WINDOW_AUTOSIZE
the user cannot resize the window, the size is constrainted by the image displayed.
Definition: highgui.hpp:184
Moments moments(InputArray array, bool binaryImage=false)
Calculates all of the moments up to the third order of a polygon or rasterized shape.
@ CHAIN_APPROX_SIMPLE
Definition: imgproc.hpp:448
void findContours(InputOutputArray image, OutputArrayOfArrays contours, OutputArray hierarchy, int mode, int method, Point offset=Point())
Finds contours in a binary image.
@ RETR_TREE
Definition: imgproc.hpp:436
void circle(InputOutputArray img, Point center, int radius, const Scalar &color, int thickness=1, int lineType=LINE_8, int shift=0)
Draws a circle.