Extract contours from bounding-box

Question

I have found this example which talk about SWT contours: Extracting text OpenCV

In my example (below) works pretty good but I need one more thing from the code: the rectangles which it detect (with inside the text) should be extracted one by one.

How can I do that having the following code ? I think about a loop but I don't know how to do it.

import cv2

image = cv2.imread("card.png")
gray = cv2.cvtColor(image,cv2.COLOR_BGR2GRAY) # grayscale
_,thresh = cv2.threshold(gray,150,255,cv2.THRESH_BINARY_INV) # threshold
kernel = cv2.getStructuringElement(cv2.MORPH_CROSS,(3,3))
dilated = cv2.dilate(thresh,kernel,iterations = 13) # dilate
_, contours, hierarchy = cv2.findContours(dilated,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE) # get contours

# for each contour found, draw a rectangle around it on original image
for contour in contours:
    # get rectangle bounding contour
    [x,y,w,h] = cv2.boundingRect(contour)

    # discard areas that are too large
    if h>300 and w>300:
        continue

    # discard areas that are too small
    if h<40 or w<40:
        continue

    # draw rectangle around contour on original image
    cv2.rectangle(image,(x,y),(x+w,y+h),(255,0,255),2)

# write original image with added contours to disk  
cv2.imwrite("contoured.jpg", image)

As requested, this is the original image:

1

Post your original image. – zindarod Sep 01 '17 at 15:09

score 3 · Answer 1 · answered Sep 01 '17 at 16:47

3

first use morpological operations to make sure that all digits are well formed and remove noise and afterword use findcontour function to get each digit separately

answered Sep 01 '17 at 16:47

vasu gupta

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Hi Take a look at my (self) answer. It seems to do the job fine: [answer](https://stackoverflow.com/questions/46001090/detect-space-between-text-opencv-python/46002089#46002089) – lucians Sep 04 '17 at 08:31

score 0 · Answer 2 · answered Sep 04 '17 at 08:32

Used this code to do the job. It detects region of text/digits in images.

import cv2

image = cv2.imread("C:\\Users\\Bob\\Desktop\\PyHw\\images\\test5.png")
gray = cv2.cvtColor(image,cv2.COLOR_BGR2GRAY) # grayscale
_,thresh = cv2.threshold(gray,150,255,cv2.THRESH_BINARY_INV) # threshold
kernel = cv2.getStructuringElement(cv2.MORPH_CROSS,(3,3))
dilated = cv2.dilate(thresh,kernel,iterations = 13) # dilate
_, contours, hierarchy = cv2.findContours(dilated,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE) # get contours


idx =0
# for each contour found, draw a rectangle around it on original image
for contour in contours:

    idx += 1

    # get rectangle bounding contour
    [x,y,w,h] = cv2.boundingRect(contour)

    # discard areas that are too large
    if h>300 and w>300:
        continue

    # discard areas that are too small
    if h<40 or w<40:
        continue

    # draw rectangle around contour on original image
    #cv2.rectangle(image,(x,y),(x+w,y+h),(255,0,255),2)

    roi = image[y:y + h, x:x + w]

    cv2.imwrite('C:\\Users\\Bob\\Desktop\\' + str(idx) + '.jpg', roi)

    cv2.imshow('img',roi)
    cv2.waitKey(0)

The code is based on this other question/answer: Extracting text OpenCV

Extract contours from bounding-box

2 Answers2