使用OpenCV在iOS中进行透视变换+裁剪

Question

我正在尝试实施裁剪和放大透视校正功能进入即将推出的应用。在做研究的同时，我遇到了：

Executing cv::warpPerspective for a fake deskewing on a set of cv::Point

http://sudokugrab.blogspot.ch/2009/07/how-does-it-all-work.html

所以我决定尝试用OpenCV实现这个功能 - 框架就在那里，所以安装很快。但是，我没有得到我希望的结果:(第二张图片是结果）

我已经翻译了所有代码以使用Xcode并三次检查了坐标。你能告诉我我的代码有什么问题吗？为了完整起见，我还包括了UIImage - ＆gt; Mat转换+逆转：

- (void)confirmedImage
{
    if ([_adjustRect frameEdited]) {

    cv::Mat src = [self cvMatFromUIImage:_sourceImage];

    // My original Coordinates
    // 4-------3
    // |       |
    // |       |
    // |       |
    // 1-------2

    CGFloat scaleFactor =  [_sourceImageView contentScale];
    CGPoint p1 = [_adjustRect coordinatesForPoint:4 withScaleFactor:scaleFactor];
    CGPoint p2 = [_adjustRect coordinatesForPoint:3 withScaleFactor:scaleFactor];
    CGPoint p3 = [_adjustRect coordinatesForPoint:1 withScaleFactor:scaleFactor];
    CGPoint p4 = [_adjustRect coordinatesForPoint:2 withScaleFactor:scaleFactor];

    std::vector<cv::Point2f> c1;
    c1.push_back(cv::Point2f(p1.x, p1.y));
    c1.push_back(cv::Point2f(p2.x, p2.y));
    c1.push_back(cv::Point2f(p3.x, p3.y));
    c1.push_back(cv::Point2f(p4.x, p4.y));

    cv::RotatedRect box = minAreaRect(cv::Mat(c1));
    cv::Point2f pts[4];
    box.points(pts);

    cv::Point2f src_vertices[3];
    src_vertices[0] = pts[0];
    src_vertices[1] = pts[1];
    src_vertices[2] = pts[3];

    cv::Point2f dst_vertices[4];
    dst_vertices[0].x = 0;
    dst_vertices[0].y = 0;

    dst_vertices[1].x = box.boundingRect().width-1;
    dst_vertices[1].y = 0;

    dst_vertices[2].x = 0;
    dst_vertices[2].y = box.boundingRect().height-1;

    dst_vertices[3].x = box.boundingRect().width-1;
    dst_vertices[3].y = box.boundingRect().height-1;

    cv::Mat warpAffineMatrix = getAffineTransform(src_vertices, dst_vertices);

    cv::Mat rotated;
    cv::Size size(box.boundingRect().width, box.boundingRect().height);
    warpAffine(src, rotated, warpAffineMatrix, size, cv::INTER_LINEAR, cv::BORDER_CONSTANT);


    [_sourceImageView setNeedsDisplay];
    [_sourceImageView setImage:[self UIImageFromCVMat:rotated]];
    [_sourceImageView setContentMode:UIViewContentModeScaleAspectFit];

    rotated.release();
    src.release();

    }
}

- (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, rows, cols), image.CGImage );
    CGContextRelease( contextRef );
    CGColorSpaceRelease( colorSpace );
    return cvMat;
}

这是解决我问题的正确方法吗？你有任何可以帮我解决的示例代码吗？

感谢您阅读我的问题！

UDATE：

我实际上在这里开源了我的UIImagePickerController替代品：https://github.com/mmackh/MAImagePickerController-of-InstaPDF 其中包括可调裁剪视图，滤镜和透视校正。

Answer 1

我认为getAffineTransform中的点对应是不正确的。

检查box.points(pts);

输出的点坐标

为什么不使用p1 p2 p3 p4来计算转换？