Face comparison

How it works

Submit a face comparison task with the URLs of two images. The SDK sends an ImageSyncScanRequest to the Content Moderation service with the sface-1 scene, which performs facial attribute detection.

Face comparison supports two detection modes:

• Synchronous detection: Returns results immediately. Use this for real-time scenarios. For request and response parameters, see the Synchronous Detection API reference.

• Asynchronous detection: Submits a task and returns results via polling or a callback notification. Use this for batch processing or when you do not need an immediate response. For parameters, see Asynchronous moderation.

Prerequisites

Before you begin, make sure you have:

• Installed the Content Moderation SDK for .NET dependencies. For installation steps, see Installation.

• Used the .NET version specified in the Installation guide. Using a different version causes operation calls to fail.

• Two publicly accessible face image URLs (HTTP or HTTPS, max 2,048 characters each).

• An AccessKey ID and AccessKey secret for a Resource Access Management (RAM) user with permission to call Content Moderation APIs. Store these as environment variables.

Submit a face comparison task

The following example submits a synchronous face comparison task. All requests use the sface-1 scene to compare face image 1 (url) against face image 2 (faceUrl).

using System;
using Newtonsoft.Json;
using Aliyun.Acs.Core;
using Aliyun.Acs.Core.Http;
using Aliyun.Acs.Core.Profile;
using Aliyun.Acs.Green.Model.V20180509;
using System.Collections.Generic;

namespace csharp_sdk_sample
{
    class Program
    {
        static void Main(string[] args)
        {
            // Retrieve credentials from environment variables.
            // Do not hardcode credentials in your code.
            DefaultProfile profile = DefaultProfile.GetProfile(
                    "cn-shanghai",
                    Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_ID"),
                    Environment.GetEnvironmentVariable("ALIBABA_CLOUD_ACCESS_KEY_SECRET"));

            // Reuse the client instance to improve performance and avoid repeated connections.
            DefaultAcsClient client = new DefaultAcsClient(profile);

            ImageSyncScanRequest request = new ImageSyncScanRequest();
            request.AcceptFormat = FormatType.JSON;
            request.ContentType = FormatType.JSON;
            request.Method = MethodType.POST;
            request.Encoding = "UTF-8";

            // faceUrl: the URL of face image 2 to compare against.
            Dictionary<string, object> extras = new Dictionary<string, object>();
            extras.Add("faceUrl", "<face-image-2-url>");

            // url: the URL of face image 1 (the source image).
            Dictionary<string, object> task1 = new Dictionary<string, object>();
            task1.Add("dataId", "<data-id>");
            task1.Add("url", "<face-image-1-url>");
            task1.Add("extras", extras);

            // scenes: set to "sface-1" for face comparison.
            // bizType: your business scenario identifier.
            Dictionary<string, object> httpBody = new Dictionary<string, object>();
            httpBody.Add("scenes", new List<string> { "sface-1" });
            httpBody.Add("bizType", "<business-scenario>");
            httpBody.Add("tasks", new List<Dictionary<string, object>> { task1 });

            request.SetContent(
                System.Text.Encoding.Default.GetBytes(JsonConvert.SerializeObject(httpBody)),
                "utf-8",
                FormatType.JSON);

            try
            {
                ImageSyncScanResponse response = client.GetAcsResponse(request);
                if (response.HttpResponse.Status != 200)
                {
                    Console.WriteLine("Request failed. Status: {0}", response.HttpResponse.Status);
                }
                Console.WriteLine(System.Text.Encoding.Default.GetString(response.HttpResponse.Content));
            }
            catch (Exception ex)
            {
                Console.WriteLine("Failed with error: {0}", ex.Message);
            }
        }
    }
}

Replace the following placeholders before running the code:

Usage notes

• Client reuse: Instantiate DefaultAcsClient once and reuse it across requests. Creating a new client per request degrades performance and increases connection overhead.

• Credentials: Store your AccessKey ID and AccessKey secret as environment variables (ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET). Hardcoding credentials in source code is a security risk.

• Image requirements: Both image URLs must be publicly accessible. The SDK does not support local files, binary data, or private URLs requiring authentication.

What's next

• To use asynchronous detection instead, see Asynchronous moderation.

• For the full list of request and response parameters for synchronous detection, see the Synchronous Detection API reference.