Convert png image bytes to numpy array

png_to_numpy.py

import numpy as np
from io import BytesIO
from PIL import Image

def png_bytes_to_numpy(png):
    """Convert png bytes to numpy array
    
    Example:  
    
    >>> fig = go.Figure(go.Scatter(x=[1], y=[1]))
    >>> plt.imshow(png_bytes_to_numpy(fig.to_image('png')))
    """
    return np.array(Image.open(BytesIO(png)))

how can i fix that error

You may have gotten your raw image bytes in a way that is unsupported by Pillow:

import io
from pathlib import Path

from PIL import Image

image_path = Path("image.png")
with image_path.open("rb") as fh:
    raw_image: bytes = fh.read()

raw_image_buffer = io.BytesIO(raw_image)
# `.seek(0)` moves the current position in the buffer to the beginning of the file.
# This ensures you read the entire buffer if you call `.read()` on it.
# If you don't do this, `.read()` will return no data because you are at the end of the buffer.
# Assigning to `_` designates that we don't want the value returned by `.seek(0)`.
# This prevents the output from displaying in the REPL.
_ = raw_image_buffer.seek(0)
# This will load the PNG correctly.
image = Image.open(raw_image_buffer)

# Lets set up an incorrect example:
raw_image_2 = image.tobytes()
raw_image_buffer_2 = io.BytesIO(raw_image_2)
_ = raw_image_buffer_2.seek(0)
image2 = Image.open(raw_image_buffer_2)
# PIL.UnidentifiedImageError: cannot identify image file

Why did this error occur, even though we went from bytes -> BytesIO -> PIL.Image.Image like in the first example? It is because the PIL.Image.Image method .tobytes() returns the pixel data of an image, not a fully encoded image. When you try to use Image.open on just pixel data, it can't determine the filetype, because there is no filetype for that data at all, just raw pixels.

Fixing our incorrect example:

raw_image_buffer_3 = io.BytesIO()
# We save the image data to a file-like object (in this case, our BytesIO object).
# `format="PNG"` is required when writing to a BytesIO object here.
# This because there is no file extension for Pillow to infer the filetype automatically.
image.save(raw_image_buffer_3, format="PNG")
_ = raw_image_buffer_3.seek(0)
image3 = Image.open(raw_image_buffer_3)
# Success!