I need something like here OpenCV C++/Obj-C: Detecting a sheet of paper / Square Detection
My code is working like a charm when my background and foreground is not the same, but if my background is almost the same color as the document it can't work anymore.
Here is the picture with a beige bg + almost beige document what is not working.. Can somebody help in this how can I fix this code?
https://i.imgur.com/81DrIIK.jpg
and the code is here:
vector<Point> getPoints(Mat image)
{
int width = image.size().width;
int height = image.size().height;
Mat image_proc = image.clone();
vector<vector<Point> > squares;
// blur will enhance edge detection
Mat blurred(image_proc);
medianBlur(image_proc, blurred, 9);
Mat gray0(blurred.size(), CV_8U), gray;
vector<vector<Point> > contours;
// find squares in every color plane of the image
for (int c = 0; c < 3; c++)
{
int ch[] = {c, 0};
mixChannels(&blurred, 1, &gray0, 1, ch, 1);
// try several threshold levels
const int threshold_level = 2;
for (int l = 0; l < threshold_level; l++)
{
// Use Canny instead of zero threshold level!
// Canny helps to catch squares with gradient shading
if (l == 0)
{
Canny(gray0, gray, 10, 20, 3); //
// Dilate helps to remove potential holes between edge segments
dilate(gray, gray, Mat(), Point(-1,-1));
}
else
{
gray = gray0 >= (l+1) * 255 / threshold_level;
}
// Find contours and store them in a list
findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
// Test contours
vector<Point> approx;
for (size_t i = 0; i < contours.size(); i++)
{
// approximate contour with accuracy proportional
// to the contour perimeter
approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);
// Note: absolute value of an area is used because
// area may be positive or negative - in accordance with the
// contour orientation
if (approx.size() == 4 &&
fabs(contourArea(Mat(approx))) > 1000 &&
isContourConvex(Mat(approx)))
{
double maxCosine = 0;
for (int j = 2; j < 5; j++)
{
double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
maxCosine = MAX(maxCosine, cosine);
}
if (maxCosine < 0.3)
squares.push_back(approx);
}
}
}
double largest_area = -1;
int largest_contour_index = 0;
for(int i=0;i<squares.size();i++)
{
double a =contourArea(squares[i],false);
if(a>largest_area)
{
largest_area = a;
largest_contour_index = i;
}
}
__android_log_print(ANDROID_LOG_VERBOSE, APPNAME, "Scaning size() %d",squares.size());
vector<Point> points;
if(squares.size() > 0)
{
points = squares[largest_contour_index];
}
else
{
points.push_back(Point(0, 0));
points.push_back(Point(width, 0));
points.push_back(Point(0, height));
points.push_back(Point(width, height));
}
return points;
}
}
Thanks
You can do threshold operation in S space of HSV-color-space. https://en.wikipedia.org/wiki/HSL_and_HSV#General_approach
I just split the channels of BGR and HSV as follow. More operations are needed.
Related
how can shapes like the ones in the photo can be recognized? I'd like to achieve it with an iOS-app, but the only that's recognized currently is the red square which is filled out.
I'm using OpenCV version 2.4.9 on iOS 8.
// Convert to grayscale
cv::Mat gray;
cv::cvtColor(src, gray, CV_BGR2GRAY);
// Convert to binary image using Canny
cv::Mat bw;
cv::Canny(gray, bw, 0, 50, 5);
imageView.image = [UIImage fromCVMat:gray];
// Find contours
std::vector<std::vector<cv::Point> > contours;
cv::findContours(bw.clone(), contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE);
// The array for storing the approximation curve
std::vector<cv::Point> approx;
// We'll put the labels in this destination image
cv::Mat dst = src.clone();
for (int i = 0; i < contours.size(); i++)
{
// Approximate contour with accuracy proportional
// to the contour perimeter
cv::approxPolyDP(
cv::Mat(contours[i]),
approx,
cv::arcLength(cv::Mat(contours[i]), true) * 0.02,
true
);
BOOL area = std::fabs(cv::contourArea(contours[i])) < 10;
BOOL convex = false; // !cv::isContourConvex(approx);
// Skip small or non-convex objects
if (area || convex) {
if (area) {
NSLog(#"contourarea : %f", std::fabs(cv::contourArea(contours[i])));
} else {
NSLog(#"convex : %i", !cv::isContourConvex(approx));
}
NSLog(#"=========");
continue;
}
if (approx.size() == 1) {
setLabel(dst, "TRI", contours[i]); // Triangles
} else if (approx.size() >= 4 && approx.size() <= 6) {
// Number of vertices of polygonal curve
int vtc = approx.size();
// Get the degree (in cosines) of all corners
std::vector<double> cos;
for (int j = 2; j < vtc+1; j++) {
cos.push_back(angle(approx[j%vtc], approx[j-2], approx[j-1]));
}
// Sort ascending the corner degree values
std::sort(cos.begin(), cos.end());
// Get the lowest and the highest degree
double mincos = cos.front();
double maxcos = cos.back();
// Use the degrees obtained above and the number of vertices
// to determine the shape of the contour
if (vtc == 4 && mincos >= -0.1 && maxcos <= 0.3)
{
// Detect rectangle or square
cv::Rect r = cv::boundingRect(contours[i]);
double ratio = std::abs(1 - (double)r.width / r.height);
setLabel(dst, ratio <= 0.02 ? "SQU" : "RECT", contours[i]);
}
else if (vtc == 5 && mincos >= -0.34 && maxcos <= -0.27)
setLabel(dst, "PENTA", contours[i]);
else if (vtc == 6 && mincos >= -0.55 && maxcos <= -0.45)
setLabel(dst, "HEXA", contours[i]);
}
else
{
// Detect and label circles
double area = cv::contourArea(contours[i]);
cv::Rect r = cv::boundingRect(contours[i]);
int radius = r.width / 2;
if (std::abs(1 - ((double)r.width / r.height)) <= 0.2 &&
std::abs(1 - (area / (CV_PI * std::pow(radius, 2)))) <= 0.2) {
}
}
} // end of for() loop
Im trying to detect the colour of a set of shapes in a black image using OpenCV, for which I use Canny detection. However the color output always comes back as black.
std::vector<std::pair<cv::Point, cv::Vec3b> > Asteroids::DetectPoints(const cv::Mat &image)
{
cv::Mat imageGray;
cv::cvtColor( image, imageGray, CV_BGR2GRAY );
cv::threshold(imageGray, imageGray, 1, 255, cv::THRESH_BINARY);
cv::Mat canny_output;
std::vector<std::vector<cv::Point> > contours;
std::vector<cv::Vec4i> hierarchy;
int thresh = 10;
// Detect edges using canny
cv::Canny( imageGray, canny_output, thresh, thresh*2, 3 );
// Find contours
cv::findContours( canny_output, contours, hierarchy, CV_RETR_LIST, CV_CHAIN_APPROX_NONE, cv::Point(0, 0) );
std::vector<std::pair<cv::Point, cv::Vec3b> > points;
for(unsigned int i = 0; i < contours.size(); i++ )
{
cv::Rect rect = cv::boundingRect(contours[i]);
std::pair<cv::Point, cv::Vec3b> posColor;
posColor.first = cv::Point( rect.tl().x + (rect.size().width / 2), rect.tl().y + (rect.size().height / 2));
posColor.second = image.at<cv::Vec3b>( posColor.first.x, posColor.first.y );
//Dont add teh entry to the list if one with the same color and position is already pressent,
//The contour detection sometimes returns duplicates
bool isInList = false;
for(unsigned int j = 0; j < points.size(); j++)
if(points[j].first == posColor.first && points[j].second == posColor.second)
isInList = true;
if(!isInList)
points.push_back( posColor );
}
return points;
}
I know it has to be an issue with the positions or something along those lines, but I cant figure out what
I might be wrong, but off the top of my head :
Shouldn't this read
posColor.second = image.at<cv::Vec3b>(posColor.first.y, posColor.first.x);
and not the other way around like you did it ?
Matrix notation, not cartesian notation ?
working on square detection. the problem is on the radiant floor. as you can see pictures.
any idea for solve this problem ?
thank you.
source image :
output :
source code:
void EdgeDetection::find_squares(const cv::Mat& image,
vector >& squares,cv::Mat& outputFrame) {
unsigned long imageSize = (long) (image.rows * image.cols) / 1000;
if (imageSize > 1200) RESIZE = 9;
else if (imageSize > 600) RESIZE = 5;
else if (imageSize > 300) RESIZE = 3;
else RESIZE = 1;
Mat src(Size(image.cols / RESIZE, image.rows / RESIZE),CV_YUV420sp2BGR);
// Resize src to img size
resize(image, src, src.size() ,0.5, 0.5, INTER_LINEAR);
Mat imgeorj=image;
const int N = 10;//11;
Mat pyr, timg, gray0(src.size(), CV_8U), gray;
// down-scale and upscale the image to filter out the noise
pyrDown(src, pyr, Size(src.cols / 2, src.rows / 2));
pyrUp(pyr, timg, src.size());
#ifdef blured
Mat blurred(src);
medianBlur(src, blurred, 15);
#endif
vector<vector<Point> > contours;
// find squares in every color plane of the image
for ( int c = 0; c < 3; ++c) {
int ch[] = {c, 0};
mixChannels(&timg, 1, &gray0, 1, ch, 1);
// try several threshold levels
for ( int l = 0; l < N; ++l) {
// hack: use Canny instead of zero threshold level.
// Canny helps to catch squares with gradient shading
if (l == 0) {
// apply Canny. Take the upper threshold from slider
// and set the lower to 0 (which forces edges merging)
// Canny(gray0, gray, 0, thresh, 5);
// Canny(gray0, gray, (10+l), (10+l)*3, 3);
Canny(gray0, gray,50, 200, 3 );
// dilate canny output to remove potential
// holes between edge segments
dilate(gray, gray, Mat(), Point(-1, -1));
//erode(gray, gray, Mat(), Point(-1, -1), 1);
} else {
// apply threshold if l!=0:
// tgray(x,y) = gray(x,y) < (l+1)*255/N ? 255 : 0
gray = gray0 >= (l + 1) * 255 / N;
}
// find contours and store them all as a list
findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
vector<Point> approx;
// test each contour
for (size_t i = 0; i < contours.size(); ++i) {
// approximate contour with accuracy proportional
// to the contour perimeter
approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true) * 0.02, true);
if (approx.size() == 4 &&
fabs(contourArea(Mat(approx))) > 5000 &&
isContourConvex(Mat(approx))) {
float maxCosine = 0;
for (register int j = 2; j < 5; ++j) {
// find the maximum cosine of the angle between joint edges
float cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
maxCosine = MAX(maxCosine, cosine);
}
// if cosines of all angles are small
// (all angles are ~90 degree) then write quandrange
// vertices to resultant sequence
if (maxCosine < 0.3) {
squares.push_back(approx);
}
}
}
}
}
debugSquares(squares, imgeorj,outputFrame);
}
You can try using Hough transform for detecting straight edges and use the those for constructing the square.
First of all sorry if question was asked. I am working on an app that can detect the corner of a document. I am right now using openCV to detect edge. I have achieved this using openCV but I am not getting the perfect result.
I have also tried the BradLarson GPUImage but I am able how to start with this.
My code that detect the corner of the document but not a perfect result.
void find_squares(Mat& image, cv::vector<cv::vector<cv::Point>>&squares)
{
// blur will enhance edge detection
Mat blurred(image);
//cv::resize(image, image, cvSize(0.25, 0.25));
Mat gray0(blurred.size(), CV_8U), gray;
//medianBlur(image, blurred, 9); //default 9;
GaussianBlur(image, blurred, cvSize(9, 9), 2.0,2.0);
vector<vector<cv::Point> > contours;
// find squares in every color plane of the image
for (int c = 0; c < 3; c++)
{
int ch[] = {c, 0};
mixChannels(&blurred, 1, &gray0, 1, ch, 1);
// try several threshold levels
const int threshold_level = 4;
for (int l = 0; l < threshold_level; l++)
{
// Use Canny instead of zero threshold level!
// Canny helps to catch squares with gradient shading
if (l == 0)
{
Canny(gray0, gray, 10, 20, 3); //
// Dilate helps to remove potential holes between edge segments
dilate(gray, gray, Mat(), cv::Point(-1,-1));
}
else
{
gray = gray0 >= (l+1) * 255 / threshold_level;
}
// Find contours and store them in a list
findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
// Test contours
vector<cv::Point> approx;
for (size_t i = 0; i < contours.size(); i++)
{
// approximate contour with accuracy proportional
// to the contour perimeter
approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);
// Note: absolute value of an area is used because
// area may be positive or negative - in accordance with the
// contour orientation
if (approx.size() == 4 &&
fabs(contourArea(Mat(approx))) > 1000 &&
isContourConvex(Mat(approx)))
{
double maxCosine = 0;
for (int j = 2; j < 5; j++)
{
double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
maxCosine = MAX(maxCosine, cosine);
}
if (maxCosine < 0.3)
squares.push_back(approx);
}
}
}
}
}
So my questions are:
1) is there any other library that can do this.
2) is there any problem in above code? Should I add some image processing before detection?
3) Can BradLarson GPUImage do this? And if it can then are there sources of sample code for edge detection?
Here is the out put of square-detection example my problem is filter this squares
first problem is its drawing one than more lines for same area;
second one is i just need to detect object not all image.
The other problem is i have to take just biggest object except all image.
Here is a code for detection:
static void findSquares( const Mat& image, vector >& squares ){
squares.clear();
Mat pyr, timg, gray0(image.size(), CV_8U), gray;
// down-scale and upscale the image to filter out the noise
pyrDown(image, pyr, Size(image.cols/2, image.rows/2));
pyrUp(pyr, timg, image.size());
vector<vector<Point> > contours;
// find squares in every color plane of the image
for( int c = 0; c < 3; c++ )
{
int ch[] = {c, 0};
mixChannels(&timg, 1, &gray0, 1, ch, 1);
// try several threshold levels
for( int l = 0; l < N; l++ )
{
// hack: use Canny instead of zero threshold level.
// Canny helps to catch squares with gradient shading
if( l == 0 )
{
// apply Canny. Take the upper threshold from slider
// and set the lower to 0 (which forces edges merging)
Canny(gray0, gray, 0, thresh, 5);
// dilate canny output to remove potential
// holes between edge segments
dilate(gray, gray, Mat(), Point(-1,-1));
}
else
{
// apply threshold if l!=0:
gray = gray0 >= (l+1)*255/N;
}
// find contours and store them all as a list
findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
vector<Point> approx;
// test each contour
for( size_t i = 0; i < contours.size(); i++ )
{
approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);
if( approx.size() == 4 &&
fabs(contourArea(Mat(approx))) > 1000 &&
isContourConvex(Mat(approx)) )
{
double maxCosine = 0;
for( int j = 2; j < 5; j++ )
{
// find the maximum cosine of the angle between joint edges
double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
maxCosine = MAX(maxCosine, cosine);
}
if( maxCosine < 0.3 )
squares.push_back(approx);
}
}
}
}
}
You need to take a look at the flags for findContours(). You can set a flag called CV_RETR_EXTERNAL which will return only the outer-most contour (all contours inside of it are thrown away). This will probably return the entire frame, so you'll need to narrow down the search so that it doesnt check your frame boundaries. Use the function copyMakeBorder() to accomplish this. I would also recommend removing your dilate function as it is probably causing duplicate contours on either side of a line (you might not even need the border if you remove the dilate). Here is my output: