Applying OCR
Loop through each contour and take the x and y coordinates and the width and height using the function cv2.boundingRect(). Then draw a rectangle in the image using the function cv2.rectangle() with the help of obtained x and y coordinates and the width and height. There are 5 parameters in the cv2.rectangle(), the first parameter specifies the input image, followed by the x and y coordinates (starting coordinates of the rectangle), the ending coordinates of the rectangle which is (x+w, y+h), the boundary color for the rectangle in RGB value and the size of the boundary. Now crop the rectangular region and then pass it to the tesseract to extract the text from the image. Then we open the created text file in append mode to append the obtained text and close the file.
Sample image used for the code:
# Import required packages
import cv2
import pytesseract
# Mention the installed location of Tesseract-OCR in your system
pytesseract.pytesseract.tesseract_cmd = 'System_path_to_tesseract.exe'
# Read image from which text needs to be extracted
img = cv2.imread("sample.jpg")
# Preprocessing the image starts
# Convert the image to gray scale
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
# Performing OTSU threshold
ret, thresh1 = cv2.threshold(gray, 0, 255, cv2.THRESH_OTSU | cv2.THRESH_BINARY_INV)
# Specify structure shape and kernel size.
# Kernel size increases or decreases the area
# of the rectangle to be detected.
# A smaller value like (10, 10) will detect
# each word instead of a sentence.
rect_kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (18, 18))
# Applying dilation on the threshold image
dilation = cv2.dilate(thresh1, rect_kernel, iterations = 1)
# Finding contours
contours, hierarchy = cv2.findContours(dilation, cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_NONE)
# Creating a copy of image
im2 = img.copy()
# A text file is created and flushed
file = open("recognized.txt", "w+")
file.write("")
file.close()
# Looping through the identified contours
# Then rectangular part is cropped and passed on
# to pytesseract for extracting text from it
# Extracted text is then written into the text file
for cnt in contours:
x, y, w, h = cv2.boundingRect(cnt)
# Drawing a rectangle on copied image
rect = cv2.rectangle(im2, (x, y), (x + w, y + h), (0, 255, 0), 2)
# Cropping the text block for giving input to OCR
cropped = im2[y:y + h, x:x + w]
# Open the file in append mode
file = open("recognized.txt", "a")
# Apply OCR on the cropped image
text = pytesseract.image_to_string(cropped)
# Appending the text into file
file.write(text)
file.write("\n")
# Close the file
file.close()
Output:
Final text file:
Blocks of text detected:
Text Detection and Extraction using OpenCV and OCR
OpenCV (Open source computer vision) is a library of programming functions mainly aimed at real-time computer vision. OpenCV in python helps to process an image and apply various functions like resizing image, pixel manipulations, object detection, etc. In this article, we will learn how to use contours to detect the text in an image and save it to a text file.
Required Installations:
pip install opencv-python
pip install pytesseract
OpenCV package is used to read an image and perform certain image processing techniques. Python-tesseract is a wrapper for Google’s Tesseract-OCR Engine which is used to recognize text from images.
Download the tesseract executable file from this link.
Approach:
After the necessary imports, a sample image is read using the imread function of opencv.