如何按位置对矩形数组进行排序? [英] How to sort an array of rectangles by position?

问题描述

我刚刚意识到，如果仅对包含文本的区域执行OCR处理，则速度会快很多.因此，我要做的是检测图像中的文本区域，然后对每个文本区域执行OCR处理.这是使用OpenCV进行检测文本区域"步骤的结果(我用它在图像上绘制矩形):

I've just realized that if I perform OCR process only on the regions that contain text, it would be a lot faster. So what I did were detecting the text regions in the image and then perform OCR process on each one of them. This is the result of "detecting text regions" step using OpenCV (I used it to draw the rectangles on the image):

唯一的问题是我无法按文本在原始图像上出现的顺序排列文本结果.在这种情况下，应为:

The only problem remains is I couldn't arrange the text result in the order that they appear on the original image. In this case, it should be:

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

其他一些情况:

基本上任何其他带有文字的图像.

Some other cases:

Basically any other images that have text on them.

因此，我正在尝试对矩形数组(起点，宽度和高度)进行排序，然后重新排列与它们相关的文本.

So I'm trying to sort the array of rectangles (origin point, width and height) then rearrange the text associate with them.

我不知道是否有必要，但这是我使用的代码:

I don't know if it's necessary, but here is the code I used:

我如何检测文本区域

+(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流程(使用Tesseract):

This is the OCR process (using 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);
}

推荐答案

您想要的是按y位置(y-高度/2)和x(x-宽度/2)对rect数组进行排序在同一垂直线上.

What you want is to sort the array of rects by y position (y - height/2) and then x (x - width/2) if they are on the same vertical line.

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)));
}];

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