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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."

Mominul_Islam
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  • License plate number detection isn't easy. Tesseract is not really a reliable tool to do this even if some tutorials may suggest this. You will find tons of questions regarding this topic on Stackoverflow. Did you use the sample image from the tutorial or any other? Please carefully read [ask]. – Markus Dec 15 '22 at 08:03
  • if you are dissatisfied with a tutorial you found on the internet, **contact the author** for help. – Christoph Rackwitz Dec 15 '22 at 16:13
  • if len(approx) == 4: screenCnt = approx break – toyota Supra Dec 15 '22 at 20:23

1 Answers1

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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)
Ari
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