BlueHensCTF2022 - PurQRatory Solve Scripts

convert_part1.py

#edited: knew after writing this that pdfimages from poppler.utils does the same job but easier... 

from pdf2image import convert_from_path

#doing this in batches so it doesn't killed itself (+ forlooping broke somehow soooo yea)

dpi = 300
path = "./PurQRatory.pdf"

pages = convert_from_path(path, dpi=500, output_folder="",last_page=26)

pg_no = 1
for page in pages:
    page.save(f'./converted/qr{pg_no}.jpg', 'JPEG')
    pg_no += 1

pages = convert_from_path(path, dpi=dpi, first_page=27, last_page=52)

for page in pages:
    page.save(f'./converted/qr{pg_no}.jpg', 'JPEG')
    pg_no += 1

pages = convert_from_path(path, dpi=dpi, first_page=53, last_page=78)

for page in pages:
    page.save(f'./converted/qr{pg_no}.jpg', 'JPEG')
    pg_no += 1

pages = convert_from_path(path, dpi=dpi, first_page=79, last_page=107)

for page in pages:
    page.save(f'./converted/qr{pg_no}.jpg', 'JPEG')
    pg_no += 1

convert_part2.py

from PIL import Image
qr_count = 0
for pg in range(1,108):
    path = f"./converted/qr{pg}.jpg"

    im = Image.open(path)

    width, height = im.size

    padding = 320
    bot = height-1025
    top = height/3 + 200

    for i in range(4):
        if i == 0:
            im_cropped = im.crop((padding,padding,width/2,top))
        elif i == 1:
            im_cropped = im.crop((width/2,padding,width-padding,top))
        elif i == 2:
            im_cropped = im.crop((padding,top,width/2,bot))
        else:
            im_cropped = im.crop((width/2,top,width-padding,bot))
        
        qr_count += 1

        wc,hc = im_cropped.size
        res_im = im_cropped.resize((int(wc/5),int(hc/5)),resample=Image.Resampling.NEAREST)
        res_im.save(f"./converted/final/{qr_count}.jpg")

readqr.py

import cv2

path = "./converted/final"

f = open('val.txt', 'w')
for i in range(1, 428):
    img=cv2.imread(f"{path}/{i}.jpg")
    det=cv2.QRCodeDetector()
    val, pts, st_code=det.detectAndDecode(img)
    f.write(val+'\n')

f.close()

part1 -> pdf to image
part2 -> each of the QRs in the image into it's separated thing (+ resizing so the reader works better)
part3 -> qrcode reader in opencv, was able to read all but one qrcode