来自 Google Vision API OCR 的响应 400，带有指定图像的 base64 字符串

Question

我已经阅读了How to use the Google Vision API for text detection from base64 encoded image?，但它根本没有帮助。 Cloud client library 对我来说是不可取的，因为我在 OCR 之前和期间进行了许多图像处理（例如旋转、裁剪、调整大小等）。将它们保存为新文件并将它们作为 Google Vision API 的输入重新读取是相当低效的。

因此，我直接查看了发布请求的文档：

• Using Python to send requests
• Base64 Encoding
• Optical character recognition (OCR),

以下是导致失败的最少代码：

import base64
import requests
import io

# Read the image file and transform it into a base64 string
with io.open("photos/foo.jpg", 'rb') as image_file:
    image = image_file.read()
content = base64.b64encode(image)

# Prepare the data for request
# Format copied from https://cloud.google.com/vision/docs/ocr
sending_request = {
  "requests": [
    {
      "image": {
        "content": content
      },
      "features": [
        {
          "type": "TEXT_DETECTION"
        }
      ]
    }
  ]
}

# Send the request and get the response
# Format copied from https://cloud.google.com/vision/docs/using-python
response = requests.post(
    url='https://vision.googleapis.com/v1/images:annotate?key={}'.format(API_KEY),
    data=sending_request,
    headers={'Content-Type': 'application/json'}
)

# Then get 400 code
response
# <Response [400]>
print(response.text)
{
  "error": {
    "code": 400,
    "message": "Invalid JSON payload received. Unexpected token.\nrequests=image&reque\n^",
    "status": "INVALID_ARGUMENT"
  }
}

我去了控制台，看到google.cloud.vision.v1.ImageAnnotator.BatchAnnotateImages 确实存在请求错误，但我不知道发生了什么。是不是因为requests.post中发送data的格式不对？

Answer 1

错误，"message": "Invalid JSON payload received. Unexpected token.\nrequests=image&reque\n^", 表示您正在传递非 json 格式，该格式必须是 json。因此，您应该将其转换为 json 并将其传递给请求，如下所示。

response = requests.post(
url='https://vision.googleapis.com/v1/images:annotate?key={}'.format(API_KEY),
# import json module
# dumps the object to JSON
data=json.dumps(sending_request), 
headers={'Content-Type': 'application/json'}

它将触发typeError: Object of type 'bytes' is not JSON serializable at the line of json.dumps([sending_request])，因为您没有解码 b64encode 图像。所以，先做这个然后发送请求

content = base64.b64encode(image).decode('UTF-8')