Python bytesio to base64

In similar way you can work with other files: music, PDF, excel, csv, etc. or with stream from webcam.

from flask import Flask, send_file, request #render_template, import io import random import base64 import matplotlib.pyplot as plt from PIL import Image, ImageDraw import urllib.request app = Flask(__name__) @app.route('/') def index(): return """Examples
""" + """- send image
""" + """- send image to download
""" + """- img base64
""" + """- form1 (image without changes)
""" + """- form2 (image with changes)
""" def generate_image(): """Generate plot. Save in BytesIO""" # create random plot plt.cla() # to clear it because it may keep it between sessions y = [random.randint(-10, 10) for _ in range(10)] x = list(range(10)) plt.plot(x, y) # convert to file-like object obj = io.BytesIO() # file in memory to save image without using disk plt.savefig(obj, format='png') # save in file (BytesIO) obj.seek(0) # move to beginning of file (BytesIO) to read it return obj def generate_image(): """Load file to Pillow OR generate empty file in Pillow. Draw. Save in BytesIO""" # read image from file #image = Image.open('lenna.png') # OR: create empty image image = Image.new('RGB', (300, 300), (0,0,0)) # RGB, 300x300, black # draw something draw = ImageDraw.Draw(image) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html #draw.rectangle([(10,10), (90,90)], fill=(255,0,0)) draw.rectangle([(20,20), (280,280)], outline=(255,0,0), width=3) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.rectangle draw.text((5,5), "Hello World!", anchor="ms") # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.text # convert to file-like object obj = io.BytesIO() # file in memory to save image without using disk # image.save(obj, format='png') # save in file (BytesIO) # https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.save obj.seek(0) # move to beginning of file (BytesIO) to read it # return obj def generate_image(): """Get image from url. Doesn't have .getvalue() but still has .read()""" # get from url response = urllib.request.urlopen('https://picsum.photos/300/300') return response def generate_image(): """Get image from url. Read to Pillow. Draw. Save in BytesIO""" # get from url response = urllib.request.urlopen('https://picsum.photos/300/300') # read to pillow image = Image.open(response) # # draw something draw = ImageDraw.Draw(image) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html draw.rectangle([(20,20), (280,280)], outline=(255,0,0), width=3) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.rectangle draw.text((15,5), "Hello World!") # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.text # convert to file-like data obj = io.BytesIO() # file in memory to save image without using disk # image.save(obj, format='png') # save in file (BytesIO) # https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.save obj.seek(0) # move to beginning of file (BytesIO) to read it # return obj def generate_image(): """Get image from POST data""" request # get from url response = urllib.request.urlopen('https://picsum.photos/300/300') return response @app.route('/base64') def example1(): """Convert iamge to BASE64 url""" # get images img1 = generate_image() img2 = generate_image() # convert to bases64 data1 = img1.read() # get data from file (BytesIO) data1 = base64.b64encode(data1) # convert to base64 as bytes data1 = data1.decode() # convert bytes to string data2 = img2.read() # get data from file (BytesIO) data2 = base64.b64encode(data2) # convert to base64 as bytes data2 = data2.decode() # convert bytes to string # convert to with embed image img1 = ''.format(data1) img2 = ''.format(data2) # use in HTML html = img1 + img2 return html @app.route('/send_image') def example2(): """Send to client as image which browser will display""" # get image img = generate_image() # send to client as image # it needs object which has method `read() return send_file(img, 'file.png') # name `file.png` assigned to `mimetype` @app.route('/send_file') def example3(): """Send to client as file which browser will try to download""" # get image img = generate_image() # send to client as download file (with mimetype='application/octet-stream') # it needs object which has method `read() return send_file(img, as_attachment=True, attachment_filename='file.png') # mimetype='application/octet-stream') # without name as second argument because it was mimetype @app.route('/form1', methods=['GET', 'POST']) def example4(): """Get from POST (form)""" img = '- empty -' if request.method == 'POST': if "image" in request.files: print(request.files) # get image img = request.files["image"] # it has methodn .read() so it doesn't need to # convert to bases64 data = img.read() # get data from file (BytesIO) data = base64.b64encode(data) # convert to base64 as bytes data = data.decode() # convert bytes to string # convert to with embed image img = ''.format(data) return '
Send

' + img @app.route('/form2', methods=['GET', 'POST']) def example5(): """Get from POST (form)""" img = '- empty -' if request.method == 'POST': if "image" in request.files: print(request.files) # get image img = request.files["image"] # it has methodn .read() so it doesn't need to # read to pillow image = Image.open(img) # # draw something draw = ImageDraw.Draw(image) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html draw.rectangle([(20,20), (280,280)], outline=(255,0,0), width=3) # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.rectangle draw.text((15,5), "Hello World!") # https://pillow.readthedocs.io/en/stable/reference/ImageDraw.html#PIL.ImageDraw.ImageDraw.text # convert to file-like data obj = io.BytesIO() # file in memory to save image without using disk # image.save(obj, format='png') # save in file (BytesIO) # https://pillow.readthedocs.io/en/stable/reference/Image.html#PIL.Image.Image.save obj.seek(0) # convert to bases64 data = obj.read() # get data from file (BytesIO) data = base64.b64encode(data) # convert to base64 as bytes data = data.decode() # convert bytes to string # convert to with embed image img = ''.format(data) return '
Send

' + img if __name__ == '__main__': app.run(debug=True) # matplotlib need to work in main thread so flask can't use debug 

Notes:

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Python bytesio to base64

Last updated: Jun 23, 2023
Reading time · 4 min

# Table of Contents

# Convert an Image to a Base64-encoded String in Python

To convert an image to a base64 string in Python:

1. Use the with open() statement to open the image file.
2. Use the file.read() method to read the image's contents.
3. Use the base64.b64encode() method to encode the bytes using Base64 and return a bytes-like object.

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import base64 with open('house.webp', 'rb') as image_file: base64_bytes = base64.b64encode(image_file.read()) print(base64_bytes) base64_string = base64_bytes.decode() print(base64_string) 

The code sample assumes that you have the following house.webp image in the same directory as your Python script.

You can right-click on the image and select "Save image as" to download it.

We first imported the base64 native Python module.

The module provides functions for encoding binary data to printable ASCII characters and decoding such encodings back to binary data.

The next step is to use the with open() statement to open the image file in rb (read binary) mode.

The with open() statement takes care of closing the file even if an error occurs.

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import base64 with open('house.webp', 'rb') as image_file: base64_bytes = base64.b64encode(image_file.read()) print(base64_bytes) base64_string = base64_bytes.decode() print(base64_string) 

The base64.b64encode method encodes the supplied bytes-like object using Base64 and returns the encoded bytes.

If you want to convert the base64 encoded bytes to a string, use the bytes.decode method.

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base64_string = base64_bytes.decode() print(base64_string) 

The bytes.decode() method converts the bytes object to a string and removes the b prefix.

You can also pass the encoding as an argument to the decode() method.

The default encoding is utf-8 .

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base64_string = base64_bytes.decode('utf-8') print(base64_string) 

The first argument we passed to the open() function is the path to the image file.

If you are on Windows, prefix the path with r to mark it as a raw string.

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image_path = r'C:\Users\Alice\Desktop\my-image.png' 

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Conversion between base64 and OpenCV or PIL Image

When we are building web services using Python, we often send or receive images in base64 encoded format. However, when we are doing image processing tasks, we need to use PIL or OpenCV. In this post, I will share how to convert between OpenCV or PIL image and base64 encoded image.

base64 to PIL or OpenCV image

base64 to PIL Image

In the above code, since Image.open() only accepts image path or file-like object, we first convert the base64 encoded image to BytesIO object and then read the image using PIL.

base64 to OpenCV Image

 In the above code, we first convert binary image to Numpy array, then decode the array with cv2.imdecode() . The final img is an OpenCV image in Numpy ndarray format.

PIL or OpenCV image to base64

PIL Image to base64

 In the above code, instead of saving the PIL Image object img to the disk, we save it to im_file which is a file-like object. Note that in this case, we need to specify the image format in img.save() .

OpenCV to base64 image

 In the above code, we first save the image in Numpy ndarray format to im_arr which is a one-dim Numpy array. We then get the image in binary format by using the tobytes() method of this array.

References

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