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POiOS:Retrieve rectangle shaped image from the background image
 

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  1. POiOS:Retrieve rectangle shaped image from the background image
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    <p>I am working on an implementation where I have a rectangle shaped image in an big background image. I am trying to programmatically retrieve the rectangle shaped image from the big image and retrieve text information from that particular rectangle image. I am trying to use Open-CV third party framework, but couldn't able to retrieve the rectangle image from the big background image. Could someone please guide me, how i can achieve this?</p> <p><strong>UPDATED:</strong></p> <p>I found the <a href="https://code.ros.org/trac/opencv/browser/trunk/opencv/samples/c/squares.c?rev=27" rel="nofollow">Link</a> to find out the square shapes using OpenCV. Can i get it modified for finding Rectangle shapes? Can someone guide me on this?</p> <p>UPDATED LATEST:</p> <p>I got the code finally, here is it below.</p> <pre><code> - (cv::Mat)cvMatWithImage:(UIImage *)image { CGColorSpaceRef colorSpace = CGImageGetColorSpace(image.CGImage); CGFloat cols = image.size.width; CGFloat rows = image.size.height; cv::Mat cvMat(rows, cols, CV_8UC4); // 8 bits per component, 4 channels CGContextRef contextRef = CGBitmapContextCreate(cvMat.data, // Pointer to backing data cols, // Width of bitmap rows, // Height of bitmap 8, // Bits per component cvMat.step[0], // Bytes per row colorSpace, // Colorspace kCGImageAlphaNoneSkipLast | kCGBitmapByteOrderDefault); // Bitmap info flags CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage); CGContextRelease(contextRef); return cvMat; } -(UIImage *)UIImageFromCVMat:(cv::Mat)cvMat { NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize()*cvMat.total()]; CGColorSpaceRef colorSpace; if ( cvMat.elemSize() == 1 ) { colorSpace = CGColorSpaceCreateDeviceGray(); } else { colorSpace = CGColorSpaceCreateDeviceRGB(); } //CFDataRef data; CGDataProviderRef provider = CGDataProviderCreateWithCFData( (CFDataRef) data ); // It SHOULD BE (__bridge CFDataRef)data CGImageRef imageRef = CGImageCreate( cvMat.cols, cvMat.rows, 8, 8 * cvMat.elemSize(), cvMat.step[0], colorSpace, kCGImageAlphaNone|kCGBitmapByteOrderDefault, provider, NULL, false, kCGRenderingIntentDefault ); UIImage *finalImage = [UIImage imageWithCGImage:imageRef]; CGImageRelease( imageRef ); CGDataProviderRelease( provider ); CGColorSpaceRelease( colorSpace ); return finalImage; } -(void)forOpenCV { imageView = [UIImage imageNamed:@"myimage.jpg"]; if( imageView != nil ) { cv::Mat tempMat = [imageView CVMat]; cv::Mat greyMat = [self cvMatWithImage:imageView]; cv::vector&lt;cv::vector&lt;cv::Point&gt; &gt; squares; cv::Mat img= [self debugSquares: squares: greyMat]; imageView = [self UIImageFromCVMat: img]; self.imageView.image = imageView; } } double angle( cv::Point pt1, cv::Point pt2, cv::Point pt0 ) { double dx1 = pt1.x - pt0.x; double dy1 = pt1.y - pt0.y; double dx2 = pt2.x - pt0.x; double dy2 = pt2.y - pt0.y; return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10); } - (cv::Mat) debugSquares: (std::vector&lt;std::vector&lt;cv::Point&gt; &gt;) squares : (cv::Mat &amp;)image { NSLog(@"%lu",squares.size()); // blur will enhance edge detection //cv::Mat blurred(image); cv::Mat blurred = image.clone(); medianBlur(image, blurred, 9); cv::Mat gray0(image.size(), CV_8U), gray; cv::vector&lt;cv::vector&lt;cv::Point&gt; &gt; contours; // find squares in every color plane of the image for (int c = 0; c &lt; 3; c++) { int ch[] = {c, 0}; mixChannels(&amp;image, 1, &amp;gray0, 1, ch, 1); // try several threshold levels const int threshold_level = 2; for (int l = 0; l &lt; 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, cv::Mat(), cv::Point(-1,-1)); } else { gray = gray0 &gt;= (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 cv::vector&lt;cv::Point&gt; approx; for (size_t i = 0; i &lt; contours.size(); i++) { // approximate contour with accuracy proportional // to the contour perimeter approxPolyDP(cv::Mat(contours[i]), approx, arcLength(cv::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 &amp;&amp; fabs(contourArea(cv::Mat(approx))) &gt; 1000 &amp;&amp; isContourConvex(cv::Mat(approx))) { double maxCosine = 0; for (int j = 2; j &lt; 5; j++) { double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1])); maxCosine = MAX(maxCosine, cosine); } if (maxCosine &lt; 0.3) squares.push_back(approx); } } } } NSLog(@"squares.size(): %lu",squares.size()); for( size_t i = 0; i &lt; squares.size(); i++ ) { cv::Rect rectangle = boundingRect(cv::Mat(squares[i])); NSLog(@"rectangle.x: %d", rectangle.x); NSLog(@"rectangle.y: %d", rectangle.y); if(i==squares.size()-1)////Detecting Rectangle here { const cv::Point* p = &amp;squares[i][0]; int n = (int)squares[i].size(); NSLog(@"%d",n); line(image, cv::Point(507,418), cv::Point(507+1776,418+1372), cv::Scalar(255,0,0),2,8); polylines(image, &amp;p, &amp;n, 1, true, cv::Scalar(255,255,0), 5, CV_AA); int fx1=rectangle.x; NSLog(@"X: %d", fx1); int fy1=rectangle.y; NSLog(@"Y: %d", fy1); int fx2=rectangle.x+rectangle.width; NSLog(@"Width: %d", fx2); int fy2=rectangle.y+rectangle.height; NSLog(@"Height: %d", fy2); line(image, cv::Point(fx1,fy1), cv::Point(fx2,fy2), cv::Scalar(0,0,255),2,8); } } return image; } </code></pre> <p>Thank you.</p>
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    1. COHi, Anyone help me on this please. Is there any sample for detecting a rectangle shaped image in a background image?
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    2. COIf you could [help me to install openCV correctly](http://stackoverflow.com/questions/13905471/opencv-2-4-3-ios-framework-compiler-trouble-recognising-some-c-headers), then I would be happy to help you with your problem!
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    3. COHave you actually tried _running_ squares.c (or [squares.cpp](https://github.com/Itseez/opencv/blob/master/samples/cpp/squares.cpp), the c++ version)? I've looked through the code - I can't run it (see above comment) - and it seems to me it will detect any kind of rectangle, not just squares.
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