校历优化

tests/Jiaowu.Api.Tests/CaptchaKitIntegrationTests.cs

@@ -1,6 +1,7 @@
 using CaptchaKit.AspNetCore;
 using CaptchaKit;
 using Microsoft.Extensions.DependencyInjection;
+using SkiaSharp;
 
 namespace Jiaowu.Api.Tests;
 
@@ -34,6 +35,28 @@ public sealed class CaptchaKitIntegrationTests
         Assert.True(challenge.Challenge.ImageBytes!.AsSpan().StartsWith(new byte[] { 137, 80, 78, 71 }));
     }
 
+    [Fact]
+    public void Selection_visual_keeps_the_target_character_visible_above_noise()
+    {
+        var challenge = new SkiaTextCaptchaGenerator().CreateVisualChallenge(
+            new CaptchaGenerationRequest("test", DateTimeOffset.UtcNow.AddMinutes(1), 5),
+            "A", "choice-A", CaptchaChallengeType.Selection, "请选择对应字符");
+
+        using var bitmap = SKBitmap.Decode(challenge.Challenge.ImageBytes!);
+        Assert.NotNull(bitmap);
+
+        var targetPixelCount = 0;
+        for (var y = 0; y < bitmap!.Height; y++)
+        for (var x = bitmap.Width / 4; x < bitmap.Width * 3 / 4; x++)
+        {
+            var pixel = bitmap.GetPixel(x, y);
+            if (pixel.Red <= 30 && pixel.Green is >= 40 and <= 60 && pixel.Blue is >= 70 and <= 90)
+                targetPixelCount++;
+        }
+
+        Assert.True(targetPixelCount > 20, "The target character should be visibly rendered in the image center.");
+    }
+
     [Fact]
     public void Random_generator_produces_each_enabled_challenge_type()
     {