fix alpha tests

src/ImageSharp.Drawing/DrawImage.cs

@@ -96,7 +96,7 @@ namespace ImageSharp
         /// <param name="source">The image this method extends.</param>
         /// <param name="image">The image to blend with the currently processing image.</param>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
-        /// <param name="percent">The opacity of the image image to blend. Must be between 0 and 100.</param>
+        /// <param name="percent">The opacity of the image image to blend. Must be between 0 and 1.</param>
         /// <param name="size">The size to draw the blended image.</param>
         /// <param name="location">The location to draw the blended image.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>

tests/ImageSharp.Tests/Processors/Filters/AlphaTest.cs

@@ -11,11 +11,11 @@ namespace ImageSharp.Tests
 
     public class AlphaTest : FileTestBase
     {
-        public static readonly TheoryData<int> AlphaValues
-        = new TheoryData<int>
+        public static readonly TheoryData<float> AlphaValues
+        = new TheoryData<float>
         {
-            20 ,
-            80
+            20/100f ,
+            80/100f
         };
 
         [Theory]