LeastCommonMultiple

src/ImageSharp/Common/Helpers/ImageMaths.cs

@@ -13,6 +13,30 @@ namespace SixLabors.ImageSharp
     /// </summary>
     internal static class ImageMaths
     {
+        /// <summary>
+        /// Determine the Greatest CommonDivisor (GCD) of two numbers.
+        /// </summary>
+        public static int GreatestCommonDivisor(int a, int b)
+        {
+            while (b != 0)
+            {
+                int temp = b;
+                b = a % b;
+                a = temp;
+            }
+
+            return a;
+        }
+
+        /// <summary>
+        /// Determine the Least Common Multiple (LCM) of two numbers.
+        /// </summary>
+        public static int LeastCommonMultiple(int a, int b)
+        {
+            // https://en.wikipedia.org/wiki/Least_common_multiple#Reduction_by_the_greatest_common_divisor
+            return (a / GreatestCommonDivisor(a, b)) * b;
+        }
+
         /// <summary>
         /// Returns the absolute value of a 32-bit signed integer. Uses bit shifting to speed up the operation.
         /// </summary>

tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeProfilingBenchmarks.cs

@@ -10,6 +10,8 @@ using SixLabors.ImageSharp.Processing;
 using SixLabors.ImageSharp.Processing.Processors.Transforms;
 
 using SixLabors.Primitives;
+
+using Xunit;
 using Xunit.Abstractions;
 
 namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
@@ -38,11 +40,19 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
                     });
         }
 
-        // [Fact]
-        public void PrintWeightsData()
+        [Theory]
+        [InlineData(500, 200, nameof(KnownResamplers.Bicubic))]
+        [InlineData(50, 40, nameof(KnownResamplers.Bicubic))]
+        [InlineData(40, 30, nameof(KnownResamplers.Bicubic))]
+        [InlineData(500, 200, nameof(KnownResamplers.Lanczos8))]
+        [InlineData(100, 80, nameof(KnownResamplers.Lanczos8))]
+        [InlineData(100, 10, nameof(KnownResamplers.Lanczos8))]
+        [InlineData(10, 100, nameof(KnownResamplers.Lanczos8))]
+        public void PrintWeightsData(int srcSize, int destSize, string resamplerName)
         {
-            var size = new Size(500, 500);
-            var proc = new ResizeProcessor<Rgba32>(KnownResamplers.Bicubic, 200, 200, size);
+            var size = new Size(srcSize, srcSize);
+            var resampler = (IResampler) typeof(KnownResamplers).GetProperty(resamplerName).GetValue(null);
+            var proc = new ResizeProcessor<Rgba32>(resampler, destSize, destSize, size);
 
             WeightsBuffer weights = proc.PrecomputeWeights(Configuration.Default.MemoryAllocator, proc.Width, size.Width);
 
@@ -54,16 +64,19 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
                 for (int i = 0; i < window.Length; i++)
                 {
                     float value = span[i];
-                    bld.Append(value);
+                    bld.Append($"{value,7:F4}");
                     bld.Append("| ");
                 }
 
                 bld.AppendLine();
             }
 
-            File.WriteAllText("BicubicWeights.MD", bld.ToString());
+            string outDir = TestEnvironment.CreateOutputDirectory("." + nameof(this.PrintWeightsData));
+            string fileName = $@"{outDir}\{resamplerName}_{srcSize}_{destSize}.MD";
+
+            File.WriteAllText(fileName, bld.ToString());
 
-            // this.Output.WriteLine(bld.ToString());
+            this.Output.WriteLine(bld.ToString());
         }
     }
 }

tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs

@@ -56,6 +56,30 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
             }
         }
 
+        [Theory]
+        [WithFileCollection(nameof(CommonTestImages), DefaultPixelType, 1)]
+        [WithFileCollection(nameof(CommonTestImages), DefaultPixelType, 4)]
+        [WithFileCollection(nameof(CommonTestImages), DefaultPixelType, 8)]
+        [WithFileCollection(nameof(CommonTestImages), DefaultPixelType, -1)]
+        public void Resize_WorksWithAllParallelismLevels<TPixel>(TestImageProvider<TPixel> provider, int maxDegreeOfParallelism)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            if (maxDegreeOfParallelism >= 0)
+            {
+                provider.Configuration.MaxDegreeOfParallelism = maxDegreeOfParallelism;
+            }
+
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                SizeF newSize = image.Size() * 0.5f;
+                image.Mutate(x => x.Resize((Size)newSize, false));
+                FormattableString details = $"MDP{maxDegreeOfParallelism}";
+
+                image.DebugSave(provider, details);
+                //image.CompareToReferenceOutput(ImageComparer.TolerantPercentage(0.005f), provider, details);
+            }
+        }
+
         [Theory]
         [WithTestPatternImages(100, 100, DefaultPixelType)]
         public void Resize_Compand<TPixel>(TestImageProvider<TPixel> provider)

tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs

@@ -33,7 +33,7 @@ namespace SixLabors.ImageSharp.Tests
 
         public virtual string SourceFileOrDescription => "";
 
-        public Configuration Configuration { get; set; } = Configuration.Default.Clone();
+        public Configuration Configuration { get; set; } = Configuration.CreateDefaultInstance();
 
         /// <summary>
         /// Utility instance to provide informations about the test image & manage input/output