OpenCV实战之文档扫描判卷

import cv2
import numpy as np

#图像显示
def cv_show(imgname,img):
    cv2.imshow(imgname,img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

#排序坐标函数
def order_pts(pts):
    rect=np.zeros((4,2),dtype='float32')

    s = np.sum(pts,axis=1)
    rect[0] = pts[np.argmin(s)]
    rect[2] = pts[np.argmax(s)]
    n = np.diff(pts,axis=1)
    rect[1] = pts[np.argmin(n)]
    rect[3] = pts[np.argmax(n)]

    return rect

#透视变换
def four_pts_change(img,pts):
    points = order_pts(pts)
    (tl,tr,bl,br) = points

    widthA = np.sqrt(((tr[1]-tl[1])**2)+((tr[0]-tl[0])**2))
    widthB = np.sqrt(((br[1] - bl[1]) ** 2) + ((br[0] - bl[0]) ** 2))
    width = max(int(widthA),int(widthB))

    lengthA = np.sqrt(((tr[1]-br[1])**2)+((tr[0]-br[0])**2))
    lengthB = np.sqrt(((tl[1] - bl[1]) ** 2) + ((tl[0] - bl[0]) ** 2))
    length = max(int(lengthA),int(lengthB))

    #输出图坐标
    dst = np.array([
        (0,0),
        (width-1,0),
        (width-1,length-1),
        (0,length)
    ],dtype='float32')

    M = cv2.getPerspectiveTransform(points,dst)
    wraped = cv2.warpPerspective(img,M,(width,length))
    return wraped
#正确答案
ANSWER_KEY={0:1,1:4,2:0,3:3,4:1}
# ANSWER_KEY = {0:1,1:3,2:0,3:4,4:1}

img = cv2.imread('./textcard.png')
cv_show('img',img)
orig = img.copy()
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
#高斯模糊
gaussian = cv2.GaussianBlur(gray,(3,3),0)
cv_show('gaussian',gaussian)
#边缘检测
canny = cv2.Canny(gaussian,70,150)
cv_show('canny',canny)      

#轮廓检测
cnts = cv2.findContours(canny,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)[0]
cnts = sorted(cnts,key=cv2.contourArea,reverse=True)
# cv2.drawContours(orig,cnts,-1,(149,32,190),2)
# cv_show('orig',orig)
for i in cnts:
    perix = cv2.arcLength(i,True)
    approx = cv2.approxPolyDP(i,0.01*perix,True)
    if len(approx)==4:
        screen = approx
        break
cv2.drawContours(orig,[screen],-1,(149,32,190),2)
# cv_show('orig',orig)
#透视变换
wraped = four_pts_change(img,screen.reshape(4,2))
cv_show('wraped',wraped)
wraped_gray = cv2.cvtColor(wraped,cv2.COLOR_BGR2GRAY)
#阈值处理
thresh = cv2.threshold(wraped_gray,0,255,cv2.THRESH_BINARY_INV|cv2.THRESH_OTSU)[1]
cv_show('thresh',thresh)

#检测轮廓
thresh_cnts=thresh.copy()
cnts1 = cv2.findContours(thresh_cnts,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)[0]
#白色填充轮廓
cv2.drawContours(thresh_cnts,cnts1,-1,(0,0,0),3)
cv_show('WRAPED',thresh_cnts)      

#检测圆形
questions = []
for cnt in cnts1:
    (x,y,w,h) = cv2.boundingRect(cnt)
    # print((x,y,w,h))
    arc = w/float(h)
    if w>20 and h>20 and arc >0.6 and arc<1.1:
        questions.append(cnt)
print('一共有{}个选项'.format(len(questions)))
# print(questions)

#从上到下排序
boundingBox =[ cv2.boundingRect(i) for i in questions]
(questionCnts,boundingBox) = zip(*sorted(zip(questions,boundingBox),key=lambda b:b[1][1],reverse=False))

correct =0
#每行遍历
for (q,i) in enumerate(np.arange(0,len(questions),5)):
    boundingBox = [cv2.boundingRect(c) for c in questionCnts[i:i+5]]
    (cnts,boundingBox) = zip(*sorted(zip(questionCnts[i:i+5],boundingBox),key=lambda b:b[1][0],reverse=False)) #每行从左到右排序
    bubble = None
    for (j,c) in enumerate(cnts):  #遍历每一行
        mask = np.zeros_like(thresh)
        cv2.drawContours(mask, [c], -1, 255, -1)  #不能丢
        mask = cv2.bitwise_and(thresh,thresh,mask=mask)
        # cv_show('mask', mask)
        total =  cv2.countNonZero(mask)
        if bubble is None or total>bubble[0]:
            bubble=(total,j)

    k = ANSWER_KEY[q]
    if k==bubble[1]:
        correct += 1

score = (correct/5)*100
# print(score)
print('[INFO]score : {:.2f}%'.format(score))
cv2.putText(wraped,'{:.2f}%'.format(score),(10,30),cv2.FONT_HERSHEY_SIMPLEX,0.9,(150,36,36),3)
# cv2.putText(wraped,score,(30,10),cv2.FONT_HERSHEY_SIMPLEX,0.9,(123,123,123),3)
cv_show('score',wraped)