实战 | OpenCV+OCR实现环形文字识别实例(详细步骤 + 代码)
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背景介绍
详细实现步骤
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)gray = cv2.medianBlur(gray,3)circles = cv2.HoughCircles(gray,cv2.HOUGH_GRADIENT,1,100,\param1=200,param2=30,minRadius=200,maxRadius=300)isNG = Falseif circles is None:print("找圆失败！")else:circles = np.uint16(np.around(circles))a, b, c = circles.shapeprint (circles.shape)for i in range(b):cv2.circle(img_copy, (circles[0][i][0], circles[0][i][1]), circles[0][i][2], (0, 0, 255), 3, cv2.LINE_AA)cv2.circle(img_copy, (circles[0][i][0], circles[0][i][1]), 2, (0, 255, 0), 3, cv2.LINE_AA) # draw center of circlecv2.imshow("findCircle", img_copy)
x = circles[0][i][0] - circles[0][i][2]y = circles[0][i][1] - circles[0][i][2]w = h = 2 * circles[0][i][2]center = (circles[0][i][0], circles[0][i][1])radius = circles[0][i][2]C = 2 * math.pi * radiusprint(C,radius)ROI = img[y:y+h,x:x+w].copy()cv2.imshow('ROI',ROI)trans_center = (center[0]-x, center[1]-y)polarImg = cv2.warpPolar(ROI,(int(radius),int(C)),trans_center,radius,cv2.INTER_LINEAR + cv2.WARP_POLAR_LINEAR)polarImg = cv2.flip(polarImg,1) #镜像polarImg = cv2.transpose(polarImg)#转置cv2.imshow('polarImg',polarImg)cv2.imwrite('polarImg.png',polarImg)
【3】文字识别。使用EasyOCR或PaddleOCR均可，这里使用EasyOCR。
result = reader.readtext(polarImg)print(result)if len(result) > 0:for i in range(0,len(result)):print(result[i][1])if(result[i][2] < 0.4):continuefor j in range(4):if j > 0:cv2.line(polarImg,(tuple(result[i][0][j-1])),(tuple(result[i][0][j])),(0,255,0),2,cv2.LINE_AA)cv2.line(polarImg,(tuple(result[i][0][0])),(tuple(result[i][0][3])),(0,255,0),2,cv2.LINE_AA)strText = result[i][1].replace(' ','')cv2.putText(polarImg,strText,(result[i][0][3][0],result[i][0][3][1]+20),0,0.8,(0,0,255),2)cv2.imshow('polarImg-OCR',polarImg)
【4】极坐标反变换，将包含识别结果的图像还原成圆形。
polarImg = cv2.flip(polarImg,0) #镜像polarImg = cv2.transpose(polarImg)#转置polarImg_Inv = cv2.warpPolar(polarImg,(w,h),trans_center,radius,cv2.INTER_LINEAR + \cv2.WARP_POLAR_LINEAR + cv2.WARP_INVERSE_MAP)cv2.imshow('polarImg_Inv',polarImg_Inv)
【5】创建圆形mask图像做copyTo操作，使圆形外部图像与原图保持一致。
mask = np.zeros((h,w,1),np.uint8)cv2.circle(mask,trans_center,radius-3,(255,255,255),-1, cv2.LINE_AA)cv2.imshow('mask', mask)ROI = img[y:y+h,x:x+w]for i in range(0,ROI.shape[0]):for j in range(0, ROI.shape[1]):if mask[i,j] > 0:ROI[i,j] = polarImg_Inv[i,j]cv2.imshow('result', img)cv2.waitKey(0)
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