Text Detection: Getting Bounding boxes

Question

I have a black and white image, of a text document. I want to be able to get a list of the bounding boxes for each character. I have attempted an algorithm myself, but it takes excessively long, and is only somewhat successful. Are there any python libraries I can use to find the bounding box? I've been looking into opencv but the documentation is hard to follow. And in this tutorial I can't even decipher whether the bounding boxes were found because I can't easily find what the functions actually do.

Hallucination

The LINK provided by you involves watershed algorithm. This is not required when you want to separate clear text. You better try THIS – Unthread

Answer 1

You can use boundingRect(). Make sure your image background is black and text in image is white.Using this code you can draw rectangles around text in your image. To get a list of every rectangle please add respective code segment as per your requirement.

import cv2
img = cv2.imread('input.png', 0) 
cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU,img)

image, contours, hier = cv2.findContours(img, cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)
for c in contours:
    # get the bounding rect
    x, y, w, h = cv2.boundingRect(c)
    # draw a white rectangle to visualize the bounding rect
    cv2.rectangle(img, (x, y), (x + w, y + h), 255, 1)

cv2.drawContours(img, contours, -1, (255, 255, 0), 1)

cv2.imwrite("output.png",img)

Apicella

Answer 2

I would suggest that you look into the boundingRect() function in the openCV library:

https://docs.opencv.org/2.4/doc/tutorials/imgproc/shapedescriptors/bounding_rects_circles/bounding_rects_circles.html

The documentation is based on cpp but it can be implemented in python as well.

Gathers