Python 图像与二进制格式、 str 与byte之间转换

图像转换为二进制

图像转换为二进制主要是方便数据传输，比如在web开发中，将数据从客户端传到服务端需要将客户端的数据转换为Byte类型，然后在服务端接收到数据后再将Byte类型的数据转换为图像.

• RGB图像转换为二进制方式有两种:

  • 通过url读取图像并且转换为二进制字节流

    from urllib import request
    image = request.urlopen('https://pic.cnblogs.com/avatar/875028/20160405220401.png').read()
    

  • 读入本地图像然后转换为二进制字节流

    import cv2
    with open('/media/work/data/temp.jpg', 'rb') as data:
        image = data.read()
    

• 二进制图像转换为RGB图像方式有两种

  • 通过PIL 读取二进制字节流

    from PIL import Image
    import io
    import numpy as np
    # covert byte to RGB image
    img = Image.open(io.BytesIO(image))
    # Image 转numpy
    img_np = np.array(img)
    

  • 通过cv2读取二进制字节流

    import cv2
    import numpy as np
    from PIL import Image
    # img BGR
    img = cv2.imdecode(np.frombuffer(image, np.uint8), cv2.IMREAD_COLOR)
    # covert BRG to RGB
    img_np = cv2.cvtColor(img. cv2.COLOR_RGB2BGR)
    #numpy 转Image
    img = Image.fromarray(img_np)
    

• string 与 byte　之间转换

  # bytes 
  b = b"something"
  # str 
  s = "something"
  # str to bytes two method
  b = bytes(s, encoding = "utf8")
  b = str.encode(s)
  # bytes to str two method
  s = str(b, encoding = "utf-8")
  s = bytes.decode(b)