如何按位置对矩形数组排序？

Question

我刚刚意识到，如果我只对包含文本的区域执行OCR处理，它会快得多。因此，我所做的是检测图像中的文本区域，然后对每个区域进行OCR处理。这是使用OpenCV“检测文本区域”步骤的结果（我用它在图像上绘制矩形）：

唯一的问题是我不能把文本结果按照它们出现在原始图像上的顺序排列。在这种情况下，应该是：

circle oval triangle square trapezium
diamond rhombus parallelogram rectangle pentagon
hexagon heptagon octagon nonagon decagon

基本上是任何其他有文字的图像。

+(NSMutableArray*) detectLetters:(UIImage*) image


{
    cv::Mat img;
    UIImageToMat(image, img);
    if (img.channels()!=1) {
        NSLog(@"NOT A GRAYSCALE IMAGE! CONVERTING TO GRAYSCALE.");
        cv::cvtColor(img, img, CV_BGR2GRAY);
    }
//The array of text regions (rectangle)
NSMutableArray* array = [[NSMutableArray alloc] init];

cv::Mat img_gray=img, img_sobel, img_threshold, element;

//Edge detection
cv::Sobel(img_gray, img_sobel, CV_8U, 1, 0, 3, 1, 0, cv::BORDER_DEFAULT);

cv::threshold(img_sobel, img_threshold, 0, 255, CV_THRESH_OTSU+CV_THRESH_BINARY);

element = getStructuringElement(cv::MORPH_RECT, cv::Size(17, 3) );

cv::morphologyEx(img_threshold, img_threshold, CV_MOP_CLOSE, element);

std::vector< std::vector< cv::Point> > contours;

//
cv::findContours(img_threshold, contours, 0, 1);

std::vector<std::vector<cv::Point> > contours_poly( contours.size() );


for( int i = 0; i < contours.size(); i++ )
    if (contours[i].size()>50)
    {
        cv::approxPolyDP( cv::Mat(contours[i]), contours_poly[i], 3, true );
        cv::Rect appRect( boundingRect( cv::Mat(contours_poly[i]) ));
        if (appRect.width>appRect.height){
                [array addObject:[NSValue valueWithCGRect:CGRectMake(appRect.x,appRect.y,appRect.width,appRect.height)]];
        }

    }

return array;
}

这是OCR过程（使用Tesseract）：

NSMutableArray *arr=[STOpenCV detectLetters:img];

CFTimeInterval totalStartTime = CACurrentMediaTime();
NSMutableString *res=[[NSMutableString alloc] init];

for(int i=0;i<arr.count;i++){
    NSLog(@"\n-------------\nPROCESSING REGION %d/%lu",i+1,(unsigned long)arr.count);

    //Set the OCR region using the result from last step
    tesseract.rect=[[arr objectAtIndex:i] CGRectValue];


    CFTimeInterval startTime = CACurrentMediaTime();

    NSLog(@"Start to recognize: %f",startTime);

    [tesseract recognize];

    NSString *result=[tesseract recognizedText];

    NSLog(@"Result: %@", result);
    [res appendString:result];

    CFTimeInterval elapsedTime = CACurrentMediaTime() - startTime;

    NSLog(@"FINISHED: %f", elapsedTime);
}

Answer 1

您想要的是对矩形数组按y位置（y高度/2）排序，如果它们在同一垂直线上，则按x（x宽度/2）排序。

NSArray *sortedRects;
sortedRects = [unsortedRects sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
    CGRect *first = (CGRect*)a;
    CGRect *second = (CGRect*)b;
CGFloat yDifference = first.y - (first.height / 2.0 < second.y) - (second.height / 2.0)
    return (yDifference < 0) || (yDifference == 0 && (first.x - (first.width / 2.0 < second.x) || (second.width / 2.0)));
}];