[FIXED] license plate number detection failed using opencv and pytesseract

Issue

I was just learning license plate number detection from the following link:

Tutorial Link

`My code:

import cv2
import imutils
import pytesseract
pytesseract.pytesseract.tesseract_cmd = '/usr/bin/tesseract'
image = cv2.imread('test.jpg')
image = imutils.resize(image, width=300)
cv2.imshow("original image", image)
cv2.waitKey(0)

gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
cv2.imshow("greyed image", gray_image)
cv2.waitKey(0)

gray_image = cv2.bilateralFilter(gray_image, 11, 17, 17)
cv2.imshow("smoothened image", gray_image)
cv2.waitKey(0)

edged = cv2.Canny(gray_image, 30, 200)
cv2.imshow("edged image", edged)
cv2.waitKey(0)

cnts, new = cv2.findContours(edged.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
image1 = image.copy()
cv2.drawContours(image1, cnts, -1, (0, 255, 0), 3)
cv2.imshow("contours", image1)
cv2.waitKey(0)

cnts = sorted(cnts, key=cv2.contourArea, reverse=True)[:30]
screenCnt = None
image2 = image.copy()
cv2.drawContours(image2, cnts, -1, (0, 255, 0), 3)
cv2.imshow("Top 30 contours", image2)
cv2.waitKey(0)

i = 7
for c in cnts:
    perimeter = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.018 * perimeter, True)
    if len(approx) == 4:
        screenCnt = approx

    x, y, w, h = cv2.boundingRect(c)
    new_img = image[y:y+h, x:x+w]
    cv2.imwrite('./'+str(i)+'.png', new_img)
    i += 1
    break

    cv2.drawContours(image, [screenCnt], -1, (0, 255, 0), 3)
    cv2.imshow("image with detected license plate", image)
    cv2.waitKey(0)

Cropped_loc = './7.png'
cv2.imshow("cropped", cv2.imread(Cropped_loc))

plate = pytesseract.image_to_string(Cropped_loc, lang='eng')
print("Number plate is:", plate)
cv2.waitKey(0)
cv2.destroyAllWindows()

But I cant get the expected output. I cant even troubleshoot cause there is no error. The output after executing the code "I thought it would be simple, the website is asking for more details, thats why I am talking trash in qoutation."

Solution

This part of the code needs to be inside the if statement.

x, y, w, h = cv2.boundingRect(c)
new_img = image[y:y+h, x:x+w]
cv2.imwrite('./'+str(i)+'.png', new_img)
i += 1
break

And this part of the code needs to be out of the loop.

cv2.drawContours(image, [screenCnt], -1, (0, 255, 0), 3)
cv2.imshow("image with detected license plate", image)
cv2.waitKey(0)

So your loop needs to be like this:

for c in cnts:
    perimeter = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.018 * perimeter, True)
    if len(approx) == 4:
        screenCnt = approx

        x, y, w, h = cv2.boundingRect(c)
        new_img = image[y:y+h, x:x+w]
        cv2.imwrite('./'+str(i)+'.png', new_img)
        i += 1
        break

cv2.drawContours(image, [screenCnt], -1, (0, 255, 0), 3)
cv2.imshow("image with detected license plate", image)
cv2.waitKey(0)

Answered By - Ari