Passing an image as an argument to a function in python

Question

How can I create a function that takes an image file (not image filename) in python. Simply, like the following:

FaceController.py

import cv2
from Computer_Vision import Face_Detector as FD


def detectface():
    img = cv2.imread('DSC_1902.JPG')
    FD.detect(img)


detectface()

Face_Detector.py

import cv2

def detect(img):
    face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
    for (x,y,w,h) in faces:
        img = cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
    cv2.namedWindow('img',cv2.WINDOW_NORMAL)
    cv2.imshow('img', img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()
    cv2.imwrite('messigray.png', img)
    return img

Error:

OpenCV Error: Assertion failed (!empty()) in cv::CascadeClassifier::detectMultiScale, file C:projectsopencv-pythonopencvmodulesobjdetectsrccascadedetect.cpp, line 1698
        faces = face_cascade.detectMultiScale(gray, 1.3, 5)
    cv2.error: C:projectsopencv-pythonopencvmodulesobjdetectsrccascadedetect.cpp:1698: error: (-215) !empty() in function cv::CascadeClassifier::detectMultiScale

Asked By: Mujtaba Faizi

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Source

Answer 1

You can pass a pointer pointing to the image instead of the image or the filename of the image

EDIT

def image_function(imagePointer):
    #DO SOMETHING WITH THE IMAGE

#HERE IS THE IMAGE POINTER
image = open('your_image.png')

#CALLING THE FUNCTION
image_function(image)

Sorry, I don’t know opencv so I can not help in your code 🙁

Answered By: Abhishek Chatterjee

Answer 2

You can actually pass the image as a tensor.
with cv2.imread() and torch.
Which is easy, useful.

short answer:
load with cv2.imread()
transform to tensor with
img = torch.Tensor(img)/255.

That works for my application.
Yours might be a little different.

Code answer:

from Computer_Vision import Face_Detector as FD

def detectface():
  import cv2 
  import torch
  
  folder = r"This Folder/"
  image_file = folder+"image.png"
  # or 
  # file = r"image.png"
  # image_file = os.path.join(folder, file)
  img = imread(image_file)
  
  img = torch.Tensor(img)/255. # THE KEY LINE HERE.

   FDdetect(img):
     """Do stuff with object detection..."""
     result = 
     return result

Answered By: Vince Hall

Passing an image as an argument to a function in python

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