CODEWITHSUNDEEP
pythonopencvbounding-box
lucians
lucians

Reputation: 2269

Extract contours from bounding-box

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.

example

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:

original

Upvotes: 0

Views: 1342

Answers (2)

lucians
lucians

Reputation: 2269

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

Upvotes: 0

vasu gupta
vasu gupta

Reputation: 315

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

Upvotes: 3

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