OpenCv 调整写入图像大小时显示错误

Question

def face_cropped(img):
                gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
                faces = face_classifier.detectMultiScale(gray,1.3,5)
                #scaling factor = 1.3
                #minimum neighbor = 5
                
                for (x,y,w,y) in faces:
                    face_cropped = img[y:y+h,x:x+w]
                    return face_cropped
            cap = cv2.VideoCapture(0)
            img_id = 0
            while True:
                ret,my_frame = cap.read()
                if face_cropped(my_frame) is not None:
                    img_id+=1
                face = cv2.resize(face_cropped(my_frame),(450,450))
                face = cv2.cvtColor(face, cv2.COLOR_BGR2GRAY)
                file_name_path = "data/user."+str(id)+"."+str(img_id)+".jpg"
                cv2.imwrite(file_name_path,face)
                cv2.putText(face, str(img_id),(50,50), cv2.FONT_HERSHEY_COMPLEX,2,(0,255,0),2)
                cv2.imshow("Cropped Face", face)
                
                if cv2.waitKey(0) == 13 or int(img_id) == 100:
                    break
                
            cap.release()
            cv2.destroyAllWindows()
            messagebox.showinfo("Result","Generating dataset completed!")
        except Exception as es:
            messagebox.showerror("Error",f"Due to:{str(es)}",parent=self.root)

_得到这个错误

cv2.error: OpenCV(4.5.2) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-kuwfz3h3\opencv\modules\imgproc\src\resize.cpp:4051: 错误: (-215 :断言失败).ssize:empty() 在 function 'cv::resize'

Answer 1

这里你重复了两次“y”而不是指定“h”

for (x,y,w,y) in faces:
    face_cropped = img[y:y+h,x:x+w]
    return face_cropped

那么如果 face_classifier 没有找到任何人脸，你会返回什么？ 你应该检查 faces 是否为空，在这种情况下你不能调整不存在的东西的大小。

事实上，如果你的代码找到了它工作的面孔，我只是为了测试目的而放置了一些成本值（x，y，w，h）并且调整大小没有问题：

import cv2
def face_cropped(img):
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    faces = [(100,150,234,145)]
    #scaling factor = 1.3
    #minimum neighbor = 5
    
    for (x,y,w,h) in faces:
        face_cropped = img[y:y+h,x:x+w]
        return face_cropped

cap = cv2.VideoCapture(0)
img_id = 0
while True:
    ret,my_frame = cap.read()
    if face_cropped(my_frame) is not None:
        img_id+=1
    # else:
        # continue # you can add this else statement for skipping "empty frames"

    face = cv2.resize(face_cropped(my_frame),(450,450))
    face = cv2.cvtColor(face, cv2.COLOR_BGR2GRAY)
    file_name_path = "data/user."+str(id)+"."+str(img_id)+".jpg"
    cv2.imwrite(file_name_path,face)
    cv2.putText(face, str(img_id),(50,50), cv2.FONT_HERSHEY_COMPLEX,2,(0,255,0),2)
    cv2.imshow("Cropped Face", face)
    
    if cv2.waitKey(0) == 13 or int(img_id) == 100:
        break
    
cap.release()
cv2.destroyAllWindows()

这个问题可能是由于有时输入到调整大小 function 的 object，这应该是一个框架，是无。 您可以通过添加print(type(face_cropped(my_frame)))检查它是什么