matchTemplate opencv not working as shown in opencv document

I am struggling with the problem as IN the image that I have captured from camera , I need to find the existence and location of some patterns.

For this I found to use matchTemplate method of opencv.I used the images used in the sample of opencv and wrote the code but the result is different.

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  • http://opencv.itseez.com/doc/tutorials/imgproc/histograms/template_matching/template_matching.html

    This is the link which tell us about matchTemplate.

    When I implemented it it shows the result:-

    enter image description here

    My code is below:-

    -(void)matchPatchNet
    {
        IplImage    *res;
        CvPoint     minloc, maxloc;
        double      minval, maxval;
        int         img_width, img_height;
        int         tpl_width, tpl_height;
        int         res_width, res_height;
    
    
        NSString *pathPatron = [[NSBundle mainBundle] pathForResource:@"timage" ofType:@"jpg"];
    
        UIImage *tim = [UIImage imageWithContentsOfFile:pathPatron];
        NSString *pathPatron2 = [[NSBundle mainBundle] pathForResource:@"simage" ofType:@"jpg"];
    
        UIImage *tim2 = [UIImage imageWithContentsOfFile:pathPatron2];
    
        IplImage *img = [self CreateIplImageFromUIImage:tim2];//
    
        IplImage *tpl = [self CreateIplImageFromUIImage:tim];
        cv::Mat forground1 = [tim2 CVMat];
    
        cv::Mat forground2 = [tim CVMat];
        img_width  = img->width;
        img_height = img->height;
        tpl_width  = tpl->width;
        tpl_height = tpl->height;
        res_width  = img_width - tpl_width + 1;
        res_height = img_height - tpl_height + 1;    
        res = cvCreateImage( cvSize( res_width, res_height ), IPL_DEPTH_32F, 1 );
    
        cvMatchTemplate( img, tpl, res, CV_TM_CCOEFF_NORMED );
    
        UIImage *ipala=[self UIImageFromIplImage:res];
        cv::Mat forground3 = [ipala CVMat];
        cv::normalize(forground3, forground3, 0, 1, cv::NORM_MINMAX, CV_8UC1);
    
        cvMinMaxLoc( res, &minval, &maxval, &minloc, &maxloc, 0 );    
    
        cvRectangle( img, 
                    cvPoint( maxloc.x, maxloc.y ), 
                    cvPoint( maxloc.x + tpl_width, maxloc.y + tpl_height ),
                    cvScalar( 0, 255, 0, 0 ), 1, 0, 0 ); 
        /* display images */
        self.imageView.image = [self UIImageFromIplImage:img]; 
        cvReleaseImage(&img);
        cvReleaseImage(&tpl);
        cvReleaseImage(&res);
    }
    

    Please tell me what am I doing wrong .Please help me.

    Thanks in advance

    Solutions Collect From Internet About “matchTemplate opencv not working as shown in opencv document”

    I strongly suggest you to use the C++ interface and the current docs, which you’ll find here: OpenCV v2.4.2 documentation

    Get the lastest Version of OpenCV for iOS here: OpenCV for iOS and drop it into your project and include this into your project prefixes:

    ExampleApp-Prefix.pch:

    #ifdef __cplusplus
        #import <opencv2/opencv.hpp>
    #endif
    

    Use this to “convert” UIImages to cv::Mats:

    UIImageCVMatConverter.h:

    //
    //  UIImageCVMatConverter.h
    //
    
    #import <Foundation/Foundation.h>
    
    @interface UIImageCVMatConverter : NSObject {
    
    }
    
    + (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat;
    + (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat withUIImage:(UIImage*)image;
    + (cv::Mat)cvMatFromUIImage:(UIImage *)image;
    + (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image;
    + (UIImage *)scaleAndRotateImageFrontCamera:(UIImage *)image;
    + (UIImage *)scaleAndRotateImageBackCamera:(UIImage *)image;
    
    @end
    

    UIImageCVMatConverter.mm:

    //
    //  UIImageCVMatConverter.m
    //
    
    #import "UIImageCVMatConverter.h"
    
    @implementation UIImageCVMatConverter
    
    + (UIImage *)UIImageFromCVMat:(cv::Mat)cvMat withUIImage:(UIImage*)image;
    {
      CGColorSpaceRef colorSpace = CGImageGetColorSpace( image.CGImage );
        CGFloat cols = image.size.width;
        CGFloat rows = image.size.height;
        CGFloat widthStep = image.size.width;
        CGContextRef contextRef = CGBitmapContextCreate( NULL, cols, rows, 8, widthStep*4, colorSpace, kCGImageAlphaNoneSkipLast | kCGBitmapByteOrderDefault );
        CGContextDrawImage( contextRef, CGRectMake(0, 0, cols, rows), image.CGImage );
        CGContextSetRGBStrokeColor( contextRef, 1, 0, 0, 1 );
        CGImageRef cgImage = CGBitmapContextCreateImage( contextRef );
        UIImage* result = [UIImage imageWithCGImage:cgImage];
        CGImageRelease( cgImage );
        CGContextRelease( contextRef );
        CGColorSpaceRelease( colorSpace );
        return result;
    }
    
    +(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();
        }
        CGDataProviderRef provider = CGDataProviderCreateWithCFData( (__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;
    }
    
    + (cv::Mat)cvMatFromUIImage:(UIImage *)image
    {
        CGColorSpaceRef colorSpace = CGImageGetColorSpace( image.CGImage );
        CGFloat cols = image.size.width;
        CGFloat rows = image.size.height;
        cv::Mat cvMat( rows, cols, CV_8UC4 );
        CGContextRef contextRef = CGBitmapContextCreate( cvMat.data, cols, rows, 8, cvMat.step[0], colorSpace, kCGImageAlphaNoneSkipLast | kCGBitmapByteOrderDefault );
        CGContextDrawImage( contextRef, CGRectMake(0, 0, cols, rows), image.CGImage );
        CGContextRelease( contextRef );
        CGColorSpaceRelease( colorSpace );
        return cvMat;
    }
    
    + (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image
    {
      cv::Mat cvMat = [UIImageCVMatConverter cvMatFromUIImage:image];
      cv::Mat grayMat;
        if ( cvMat.channels() == 1 ) {
            grayMat = cvMat;
      }
        else {
            grayMat = cv :: Mat( cvMat.rows,cvMat.cols, CV_8UC1 );
            cv::cvtColor( cvMat, grayMat, CV_BGR2GRAY );
        }
      return grayMat;
    }
    
    + (UIImage *)scaleAndRotateImageBackCamera:(UIImage *)image
    {
      static int kMaxResolution = 640;
      CGImageRef imgRef = image.CGImage;
      CGFloat width = CGImageGetWidth( imgRef );
      CGFloat height = CGImageGetHeight( imgRef );
      CGAffineTransform transform = CGAffineTransformIdentity;
      CGRect bounds = CGRectMake( 0, 0, width, height );
      if ( width > kMaxResolution || height > kMaxResolution ) {
        CGFloat ratio = width/height;
        if ( ratio > 1 ) {
          bounds.size.width = kMaxResolution;
          bounds.size.height = bounds.size.width / ratio;
        }
            else {
          bounds.size.height = kMaxResolution;
          bounds.size.width = bounds.size.height * ratio;
        }
      }
      CGFloat scaleRatio = bounds.size.width / width;
      CGSize imageSize = CGSizeMake( CGImageGetWidth(imgRef), CGImageGetHeight(imgRef) );
      CGFloat boundHeight;
      UIImageOrientation orient = image.imageOrientation;
      switch( orient ) {
        case UIImageOrientationUp:
          transform = CGAffineTransformIdentity;
          break;
        case UIImageOrientationUpMirrored:
          transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
          transform = CGAffineTransformScale(transform, -1.0, 1.0);
          break;
        case UIImageOrientationDown:
          transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
          transform = CGAffineTransformRotate(transform, M_PI);
          break;
        case UIImageOrientationDownMirrored:
          transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
          transform = CGAffineTransformScale(transform, 1.0, -1.0);
          break;
        case UIImageOrientationLeftMirrored:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
          transform = CGAffineTransformScale(transform, -1.0, 1.0);
          transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
          break;
        case UIImageOrientationLeft:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
          transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
          break;
        case UIImageOrientationRightMirrored:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeScale(-1.0, 1.0);
          transform = CGAffineTransformRotate(transform, M_PI / 2.0);
          break;
        case UIImageOrientationRight:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
          transform = CGAffineTransformRotate(transform, M_PI / 2.0);
          break;
        default:
          [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];
      }
      UIGraphicsBeginImageContext( bounds.size );
      CGContextRef context = UIGraphicsGetCurrentContext();
      if ( orient == UIImageOrientationRight || orient == UIImageOrientationLeft ) {
        CGContextScaleCTM( context, -scaleRatio, scaleRatio );
        CGContextTranslateCTM( context, -height, 0 );
      }
        else {
        CGContextScaleCTM( context, scaleRatio, -scaleRatio );
        CGContextTranslateCTM( context, 0, -height );
      }
      CGContextConcatCTM( context, transform );
      CGContextDrawImage( UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef );
      UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext();
      UIGraphicsEndImageContext();
      return returnImage;
    }
    
    + (UIImage *)scaleAndRotateImageFrontCamera:(UIImage *)image
    {
      static int kMaxResolution = 640;
      CGImageRef imgRef = image.CGImage;
      CGFloat width = CGImageGetWidth(imgRef);
      CGFloat height = CGImageGetHeight(imgRef);
      CGAffineTransform transform = CGAffineTransformIdentity;
      CGRect bounds = CGRectMake( 0, 0, width, height);
      if (width > kMaxResolution || height > kMaxResolution) {
        CGFloat ratio = width/height;
        if (ratio > 1) {
          bounds.size.width = kMaxResolution;
          bounds.size.height = bounds.size.width / ratio;
        } else {
          bounds.size.height = kMaxResolution;
          bounds.size.width = bounds.size.height * ratio;
        }
      }
    
      CGFloat scaleRatio = bounds.size.width / width;
      CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
      CGFloat boundHeight;
      UIImageOrientation orient = image.imageOrientation;
      switch(orient) {
        case UIImageOrientationUp:
          transform = CGAffineTransformIdentity;
          break;
        case UIImageOrientationUpMirrored:
          transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
          transform = CGAffineTransformScale(transform, -1.0, 1.0);
          break;
        case UIImageOrientationDown:
          transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
          transform = CGAffineTransformRotate(transform, M_PI);
          break;
        case UIImageOrientationDownMirrored:
          transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
          transform = CGAffineTransformScale(transform, 1.0, -1.0);
          break;
        case UIImageOrientationLeftMirrored:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
          transform = CGAffineTransformScale(transform, -1.0, 1.0);
          transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
          break;
        case UIImageOrientationLeft:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
          transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
          break;
            case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
          boundHeight = bounds.size.height;
          bounds.size.height = bounds.size.width;
          bounds.size.width = boundHeight;
          transform = CGAffineTransformMakeScale(-1.0, 1.0);
          transform = CGAffineTransformRotate(transform, M_PI / 2.0);
          break;
            default:
          [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];
      }
      UIGraphicsBeginImageContext( bounds.size );
      CGContextRef context = UIGraphicsGetCurrentContext();
      if ( orient == UIImageOrientationRight || orient == UIImageOrientationLeft ) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
      }
        else {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
      }
      CGContextConcatCTM( context, transform );
      CGContextDrawImage( UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef );
      UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext();
      UIGraphicsEndImageContext();
      return returnImage;
    }
    
    @end
    

    This is code I used to find several marker inside an image and push their center points into a std::vector:

    #import "UIImageCVMatConverter.h"
    
    ...
    
    cv::Mat src_img;
    cv::Mat result_mat;
    cv::Mat debug_img;
    cv::Mat template_img;
    
    NSArray *markerImages = [NSArray arrayWithObjects:@"marker-1.png", nil];
    
    std::vector<cv::Point> markerPoints;
    
    // input image
    src_img = [UIImageCVMatConverter cvMatFromUIImage:cameriaInputImage];
    cv::cvtColor(src_img, debug_img, CV_GRAY2BGR);
    
    for (NSString *marker in markerImages) {
        template_img = [UIImageCVMatConverter cvMatFromUIImage:[UIImage imageNamed:marker]];
        cv::cvtColor(template_img, template_img, CV_GRAY2BGR);
    
        int match_method = CV_TM_CCORR_NORMED;
    
        cv::matchTemplate(src_img, template_img, result_mat, match_method);
    
        cv::normalize(result_mat, result_mat, 0, 1, cv::NORM_MINMAX, -1, cv::Mat());
    
        double minVal;
        double maxVal;
    
        cv::Point minLoc, maxLoc, matchLoc;
        cv::minMaxLoc(result_mat, &minVal, &maxVal, &minLoc, &maxLoc, cv::Mat() );
        if ( match_method  == CV_TM_SQDIFF || match_method == CV_TM_SQDIFF_NORMED ) {
            matchLoc = minLoc;
        }
        else {
            matchLoc = maxLoc;
        }
    
        cv::Point top_left = matchLoc;
        cv::Point bottom_right = cv::Point(matchLoc.x + template_img.cols , matchLoc.y + template_img.rows);
        cv::Point center = cv::Point(0,0);
    
        center.x = (bottom_right.x + top_left.x) / 2;
        center.y = (bottom_right.y + top_left.y) / 2;
    
        markerPoints.push_back(center);
    }
    

    I hope that helps …