C#'s WriteAllBytes Equivalent Function in Python

Question

I have an image saved as a bytes array in C#. Below would be an example of how you could create such an array:

byte[] image_bytes= new byte[100] {137, 80, 78, 71, ..., 130};

Note: The above is a simplified example of I achieve the byte array. In reality, I am using Unity to generate the array. Here is a brief snippet on how I actually go about generating the byte array in case this sheds light on latter parts of the question:

camera.Render();
...
Texture2D image = new Texture2D(camera.targetTexture.width, camera.targetTexture.height);
image.ReadPixels(new Rect(0, 0, camera.targetTexture.width, camera.targetTexture.height), 0, 0);
image.Apply();
byte[] image_bytes = image.EncodeToPNG();
...

In C# I can use the function WriteAllBytes to save this image as a file that I can later open on my computer. I have tested this and thus know that the above image_bytes array is not corrupted as I can view the final image image_name.png :

File.WriteAllBytes("image_name.png", image_bytes);

The C# scirpt then sends the byte array as a JSON string over TCP connection to a python script. I have confirmed that the byte array arrives in the python script and has the same length. I have also confirmed that the first and last four bytes are the same, for example:

>>> data = json.loads(message)
>>> img_bytes = np.array(data["image"], dtype=bytes)
>>> print(img_bytes[0])
b'137'
>>> print(img_bytes[1])
b'80'
...
>>> print(img_bytes[-1])
b'130'

My goal is to eventually convert the byte array to an OpenCV frame so I can use OpenCV functions on it . However, I can't even seem to do the basics with it, for example, saving it to a file. When I try to save the data to a file in the python script, the resultant files can not be opened by standard image viewing software. I have tried a basic file save operations:

>>> with open("image_name.png", 'wb') as w:
>>>   w.write(img_bytes)

I have tried using OpenCV:

>>> img_np = cv2.imdecode(img_bytes, cv2.IMREAD_COLOR)
>>> cv2.imwrite("image_name.png", img_np)

I have also tried using PIL (Note: here I used the dimensions of the image):

>>> img_np = Image.frombytes('RGBA', (512, 384), img_bytes, 'raw')
>>> img_np.save("image_name.png")

None of the above Python save functions work (they all create files, but none of the files can be opened and viewed). What am I doing wrong? How can I save the file or even better convert the data to an OpenCV frame in Python?

TLDR: I have a byte array that represents an image in C#. I can save the byte array in C# using WriteAllBytes . I send the byte array to a Python script and have confirmed that it arrives uncorrupted. How can I save the file or even better convert the file to an OpenCV frame in Python?

Answer 1

Using dtype=bytes doesn't make sense. This makes each item a byte string , hence img_bytes[0] isn't. byte 137 , it's the byte string b'137 , because data["image"] is a list of ints.

So likely, you wanted:

img_bytes = np.array(data["image"], dtype=np.uint8)

But, you can also use:

img_bytes = bytes(data["image"])