Read text with Azure AI Vision Image Analysis

  • 6 minutes

To use Azure AI Vision for image analysis, including optical character recognition, you must provision an Azure AI Vision resource in an Azure subscription. The resource can be:

  • An Azure AI Services multi-service resource (either deployed as part of an Azure AI Foundry hub and project, or as a standalone resource).
  • A Computer Vision resource.

To use your deployed resource in an application, you must connect to its endpoint using either key-based authentication or Microsoft Entra ID authentication. You can find the endpoint for your resource in the Azure portal, or if you're working in an Azure AI Foundry project, in the Azure AI Foundry portal. The endpoint is in the form of a URL, and typically looks something like this:

https://<resource_name>.cognitiveservices.azure.com/

After establishing a connection, you can use the OCR feature by calling the ImageAnalysis function (via the REST API or with an equivalent SDK method), passing the image URL or binary data, and optionally specifying the language the text is written in (with a default value of en for English).

https://<endpoint>/computervision/imageanalysis:analyze?features=read&...

To use the Azure AI Vision Python SDK to extract text from an image, install the azure-ai-vision-imageanalysis package. Then, in your code, use either key-based authentication or Microsoft Entra ID authentication to connect an ImageAnalysisClient object to an Azure AI Vision resource. To find and read text in an image, call the analyze (or analyze_from_url) method, specifying the VisualFeatures.READ enumeration.

from azure.ai.vision.imageanalysis import ImageAnalysisClient
from azure.ai.vision.imageanalysis.models import VisualFeatures
from azure.core.credentials import AzureKeyCredential

client = ImageAnalysisClient(
    endpoint="<YOUR_RESOURCE_ENDPOINT>",
    credential=AzureKeyCredential("<YOUR_AUTHORIZATION_KEY>")
)

result = client.analyze(
    image_data=<IMAGE_DATA_BYTES>, # Binary data from your image file
    visual_features=[VisualFeatures.READ],
    language="en",
)

To use the Azure AI Vision .NET SDK to extract text from an image, install the Azure.AI.Vision.ImageAnalysis package. Then, in your code, use either key-based authentication or Microsoft Entra ID authentication to connect an ImageAnalysisClient object to an Azure AI Vision resource. To find and read text in an image, call the Analyze method, specifying the VisualFeatures.Read enumeration.

using Azure.AI.Vision.ImageAnalysis;

ImageAnalysisClient client = new ImageAnalysisClient(
    "<YOUR_RESOURCE_ENDPOINT>",
    new AzureKeyCredential("<YOUR_AUTHORIZATION_KEY>"));

ImageAnalysisResult result = client.Analyze(
    <IMAGE_DATA_BYTES>, // Binary data from your image file
    VisualFeatures.Read,
    new ImageAnalysisOptions { Language = t"en" });

The results of the Read OCR function are returned synchronously, either as JSON or the language-specific object of a similar structure. These results are broken down in blocks (with the current service only using one block), then lines, and then words. Additionally, the text values are included at both the line and word levels, making it easier to read entire lines of text if you don't need to extract text at the individual word level.

{
    "metadata":
    {
        "width": 500,
        "height": 430
    },
    "readResult":
    {
        "blocks":
        [
            {
                "lines":
                [
                    {
                        "text": "Hello World!",
                        "boundingPolygon":
                        [
                            {"x":251,"y":265},
                            {"x":673,"y":260},
                            {"x":674,"y":308},
                            {"x":252,"y":318}
                        ],
                        "words":
                        [
                            {
                                "text":"Hello",
                                "boundingPolygon":
                                [
                                    {"x":252,"y":267},
                                    {"x":307,"y":265},
                                    {"x":307,"y":318},
                                    {"x":253,"y":318}
                                ],
                            "confidence":0.996
                            },
                            {
                                "text":"World!",
                                "boundingPolygon":
                                [
                                    {"x":318,"y":264},
                                    {"x":386,"y":263},
                                    {"x":387,"y":316},
                                    {"x":319,"y":318}
                                ],
                                "confidence":0.99
                            }
                        ]
                    },
                ]
            }
        ]
    }
}