resize.cpp:4052: 错误: (-215:断言失败) !ssize.empty() 在函数 'cv::resize'

Question

我正在从我的应用程序中拍摄照片并将其上传到烧瓶上，在烧瓶上我正在运行下面的Python代码以从烧瓶中获取最近上传的图像并执行检测并从图像中提取车辆的车牌号。 我遇到的实际错误是图像正在安全且良好地上传到烧瓶上，但以上述错误的形式显示对检测无效。

from fileinput import filename
from flask import Flask, request, jsonify
import cv2
import imutils
import numpy as np
import pytesseract
import werkzeug


app = Flask(__name__)  #creating flask server


@app.route('/upload', methods=["POST"])   #defining the route of pages
def upload():
    if(request.method == "POST"):
        imagefile = request.files['image']
        imagefile2=str(imagefile)
        # print('12132')
        filename = werkzeug.utils.secure_filename(imagefile.filename)
        
        imagefile.save("./uploadedimages/"+filename)
        pytesseract.pytesseract.tesseract_cmd = r'C:\Program Files (x86)\Tesseract-OCR\tesseract.exe'
        
        img = cv2.imread(imagefile,cv2.IMREAD_COLOR)
        # print (imagefile2)
        img = cv2.resize(img, dsize=(600,400) )
        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
        gray = cv2.bilateralFilter(gray, 13, 15, 15) 
        edged = cv2.Canny(gray, 30, 200) 
        contours = cv2.findContours(edged.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
        contours = imutils.grab_contours(contours)
        contours = sorted(contours, key = cv2.contourArea, reverse = True)[:10]
        screenCnt = None
        
        for c in contours:
            peri = cv2.arcLength(c, True)
            approx = cv2.approxPolyDP(c, 0.018 * peri, True)
            
            if len(approx) == 4:
                screenCnt = approx
                break
        
        if screenCnt is None:
            detected = 0
            print ("No contour detected")
        else:
            detected = 1
            
        if detected == 1:
            cv2.drawContours(img, [screenCnt], -1, (0, 0, 255), 3)
        
        mask = np.zeros(gray.shape,np.uint8)
        new_image = cv2.drawContours(mask,[screenCnt],0,255,-1,)
        new_image = cv2.bitwise_and(img,img,mask=mask)
        
        (x, y) = np.where(mask == 255)
        (topx, topy) = (np.min(x), np.min(y))
        (bottomx, bottomy) = (np.max(x), np.max(y))
        Cropped = gray[topx:bottomx+1, topy:bottomy+1]
        
        text = pytesseract.image_to_string(Cropped, config='--psm 11')
        print("programming_fever's License Plate Recognition\n")
        print("Detected license plate Number is:",text)
        img = cv2.resize(img,(500,300))
        Cropped = cv2.resize(Cropped,(400,200))
        cv2.imshow('car',img)
        cv2.imshow('Cropped',Cropped)
        cv2.waitKey(0)
        cv2.destroyAllWindows()

        return jsonify({
            "message":"Uploaded"
        })

if __name__ == "__main__":
    app.run(debug=True, port=4000 )

我尝试过将图像转换为字符串，但没有成功。我正在使用 flutter 作为应用程序。 下面是接收烧瓶响应的应用程序屏幕代码。

uploadImage() async {
    final request = http.MultipartRequest(
        "POST", Uri.parse("https://6a6d-59-103-181-239.ngrok.io/upload"));

    final headers = {"Content-type": "multipart/form-data"};

    request.files.add(http.MultipartFile('image',
        selectedImage.readAsBytes().asStream(), selectedImage.lengthSync(),
        filename: selectedImage.path.split("/").last));

    request.headers.addAll(headers);
    final response = await request.send();
    http.Response res = await http.Response.fromStream(response);
    final resJson = jsonDecode(res.body);
    message = resJson['message'];
    setState(() {});
  }

Answer 1

OpenCV 的 cv2 绑定以神秘的方式告诉您您无意中传递了 None。这里

img = cv2.imread(imagefile,cv2.IMREAD_COLOR)

可能返回 None，可能是因为您打算传递

"./uploadedimages/"+filename

而不是 imagefile。