Sort bounding boxes with Tl() : Opencv Android

Question

I am trying to sort the bounding boxes with y axis and then x axis but the results I find from tl().x and tl().y are bit confusing and after lot of work I couldn't find anything in documentation. Here are some results please take a look. I want them to be in order from 1 to 30

CODE:

m = Utils.loadResource(MainActivity.this, R.drawable.sheet1, Highgui.CV_LOAD_IMAGE_COLOR);
//Mat original = Utils.loadResource(MainActivity.this, R.drawable.sheet1, Highgui.CV_LOAD_IMAGE_COLOR);
Bitmap bm = Bitmap.createBitmap(m.cols(), m.rows(),Bitmap.Config.ARGB_8888);

Imgproc.cvtColor(m, m, Imgproc.COLOR_BGR2GRAY);
Imgproc.medianBlur(m, m,3); 
Imgproc.threshold(m, m, 0, 255, Imgproc.THRESH_OTSU);
Core.bitwise_not(m, m);
Imgproc.dilate(m, m, Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(1,118)));

java.util.List<MatOfPoint> contours = new ArrayList<MatOfPoint>();                  
Imgproc.findContours(m.clone(), contours, new Mat() ,Imgproc.RETR_EXTERNAL , Imgproc.CHAIN_APPROX_SIMPLE);
Rect rect = Imgproc.boundingRect(contours.get(35));                         
Toast.makeText(MainActivity.this, "TL:"+rect.tl()+"BR:"+rect.br(), Toast.LENGTH_LONG).show();

enter image description here

EDIT:

This is cropped region and the coordinates showing above are of these boxes. enter image description here

Original Image:

enter image description here

Please offer some more background on the scenario and narrow the scope of your question - what, specifically, are you confused about/do you need help doing? — snickers10m, Apr 26 '15 at 23:18
If you can also list which areas of the documentation you looked to for help on your problem it can help us to get you an answer more quickly. — snickers10m, Apr 26 '15 at 23:19
Alright, please add any new information to your post with the "edit" button (beneath the tags you listed) that's the best place to put it. Then, continue with the other issues I pointed out with your question. — snickers10m, Apr 26 '15 at 23:22
@snickers10m MCQ 16 to onwards are on the right side of the image but why their y component is less ? — Zain ul abdeen, Apr 26 '15 at 23:25
@Antonio Contours are correct from bounding boxes I have cropped the region and showed them in ImageView which gives the correct boxes but fro your satisfaction I have added the code above. — Zain ul abdeen, Apr 27 '15 at 01:28
@Antonio tl().x and tl().y gives the same results and I have uploaded the image like its shown above but when it gives the resultant image it is rotated — Zain ul abdeen, Apr 27 '15 at 19:27
@HelpingDesk Ok, so the results you have are perfectly reasonable (your input image is rotated, so x and y are swapped). I struggle to understand what's your problem. — Antonio, Apr 27 '15 at 19:32
@HelpingDesk Well, isn't your input image simply rotated? If you need to rotate it after loading in opencv, you can check how this is done in C++: http://stackoverflow.com/a/23990392/2436175 — Antonio, Apr 27 '15 at 19:40
@Antonio Ok If input image is rotated I have applied dialation horizontally how does it combined the circles? — Zain ul abdeen, Apr 27 '15 at 19:43
@HelpingDesk Please ask a clear question, I still do not understand what is your problem. — Antonio, Apr 27 '15 at 20:26
@Antonio I just want at contour(0) it should be MCQ number 1 and at contour(1) MCQ number 2 and so on — Zain ul abdeen, Apr 27 '15 at 20:32
@Antonio If you look at the image above it has an index before circles in each row — Zain ul abdeen, Apr 27 '15 at 20:38

score 1 · Answer 1 · answered Apr 27 '15 at 20:48

1

So you want to sort with priority first left to right and then top to bottom. x coordinate is more important, however for similar x what counts is the y. Write a sorting function, in which you have a relationship which in pseudocode looks like this:

boolean isLessThan(bboxA,bboxB,unsigned int tolerance = 100) {

    if (bboxA.tl().x + tolerance < bboxB.tl().x);
         return true;
    if (bboxB.tl().x + tolerance < bboxA.tl().x);
         return false;
    return (bboxA.tl().y < bboxB.tl().y);

    }

(Or hardcode tolerance)

answered Apr 27 '15 at 20:48

Antonio

19,451
13
99
197

what is tolerance here? – Zain ul abdeen Apr 27 '15 at 20:55
@HelpingDesk For similar x (displacement from the left side), what counts is the y coordinate. To define "similar" you use a threshold: if their difference of their x coordinates is within this threshold, than you have to check the y coordinate. I call this threshold "tolerance". – Antonio Apr 27 '15 at 20:58

Sort bounding boxes with Tl() : Opencv Android

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