如何以二进制形式读取Django request.FILES（图像）

Question

I want to get a binary image from request which contains an image file from ajax.

Senario - When a user uploads an image file, I want to do OCR(Optical Character Recognition) to the image file using google VISION API. For that, I need to read the file as binary.

Background - Currently, In my program, when the user uploads the image, the file is passed to Django view by ajax. I tried to get a binary file in the views.py. When I use request.FILES.get('file').read() , there is no data. But print(request.FILES.get('file').name) is 'bank.png'... I think it's weird.

Here is some code

views.py

def receipt_ocr(request):
    if request.method == 'POST':
        print(type(request.FILES["file"]))              #<class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
        print(type(request.FILES.get('file')))          #<class 'django.core.files.uploadedfile.InMemoryUploadedFile'>
        print(request.FILES.get('file'))                #bank.png
        imageFile = request.FILES.get('file')
        print(imageFile.size)                           #119227
        print(request.FILES.get('file').name)           #bank.png
        print(request.FILES.get('file').content_type)   #image/png
        print(type(request.FILES.get('file').open()))   #<class 'NoneType'>
        print(request.FILES.get('file').open())         #None
        print(type(request.FILES["file"].read()))       #<class 'bytes'>
        for chunk in imageFile.chunks():
            print(chunk)                               #this generates lot of binary and some rdf:Description rdf:about= ... things
        receipt_image = imageFile.read()
        print(type(receipt_image))
        print(receipt_image)

ajax part

                // receipt OCR process
                $.ajax({
                    url: "{% url 'place:receipt_ocr' %}",
                    enctype: 'multipart/form-data',
                    type: 'POST',
                    processData: false,
                    contentType: false,
                    data: postData,
                    complete: function(req){
                        alert('good');
                    },
                    error: function(req, err){
                        alert('message:' + err);
                    }
                });

What I exactly want to do is using this kind of code (google VISION API example code, OCR)

def detect_text(path):
    """Detects text in the file."""
    client = vision.ImageAnnotatorClient()

    with io.open(path, 'rb') as image_file:
        content = image_file.read() #read binary, save to content

    image = vision.types.Image(content=content)

    response = client.text_detection(image=image)
    texts = response.text_annotations
    print('Texts:')
    print(type(texts))

    for text in texts:
        print('\n"{}"'.format(text.description))

        vertices = (['({},{})'.format(vertex.x, vertex.y)
                    for vertex in text.bounding_poly.vertices])

        print('bounds: {}'.format(','.join(vertices)))

So I want to get 'content' of above code in my views.py from the request. (I don't need to use this function itself. I'll use some part of the function)

How can I get the binary image in views.py? I thought the code below would works, but it doens't work. and I don't know why.

f = request.FILES.get('file')
receipt_image = f.read()
image = vision.types.Image(content=receipt_image)

Thank you for your any help and comments.

===ADD===

'it doesn't work' means that I got this Traceback from the log.

Internal Server Error: /mdd_event/receipt_ocr/ Traceback (most recent call last): File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\api_core\grpc_helpers.py", line 57, in error_remapped_callable return callable_(*args, **kwargs) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\grpc\_channel.py", line 565, in __call__ return _end_unary_response_blocking(state, call, False, None) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\grpc\_channel.py", line 467, in _end_unary_response_blocking raise _Rendezvous(state, None, None, deadline) grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with: status = StatusCode.INVALID_ARGUMENT details = "Request must specify image and features." debug_error_string = "{"created":"@1566165461.211000000","description":"Error received from peer ipv4:216.58.197.234:443","file":"src/core/lib/surface/call.cc","file_line":1052,"grpc_message":"Request must specify image and features.","grpc_status":3}" > 
The above exception was the direct cause of the following exception: Traceback (most recent call last): 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\django\core\handlers\exception.py", line 41, in inner response = get_response(request) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response response = self.process_exception_by_middleware(e, request) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\django\contrib\auth\decorators.py", line 23, in _wrapped_view return view_func(request, *args, **kwargs) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\django\contrib\auth\decorators.py", line 23, in _wrapped_view return view_func(request, *args, **kwargs) 
File "C:\Users\user\liam\dev\git\mdd_bean\mdd_event\views.py", line 530, in receipt_ocr response = client.text_detection(image=image) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\cloud\vision_helpers\decorators.py", line 101, in inner response = self.annotate_image(request, retry=retry, timeout=timeout) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\cloud\vision_helpers\__init__.py", line 72, in annotate_image r = self.batch_annotate_images([request], retry=retry, timeout=timeout) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\cloud\vision_v1\gapic\image_annotator_client.py", line 274, in batch_annotate_images request, retry=retry, timeout=timeout, metadata=metadata File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\api_core\gapic_v1\method.py", line 143, in __call__ return wrapped_func(*args, **kwargs) 
File "C:\Users\user\liam\dev\git\mdd_bean_env\lib\site-packages\google\api_core\grpc_helpers.py", line 59, in error_remapped_callable six.raise_from(exceptions.from_grpc_error(exc), exc) 
File "<string>", line 3, in raise_from google.api_core.exceptions.InvalidArgument: 400 Request must specify image and features.

Answer 1

I posted another question . Because this question include not one issue but some issues like 'there's no actual data but name and size', 'get binary image', 'google vision api using', ... So I decided post another one for only 'no data'issue. and there is the answer

Summary : I already read the data in request.FILES["file"].read() . So there's no data in buffer of subsequent calls.