Allow pad to work for non-alpha pixel formats

src/ImageSharp/Processing/Extensions/Transforms/PadExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 namespace SixLabors.ImageSharp.Processing
@@ -34,9 +34,10 @@ public static IImageProcessingContext Pad(this IImageProcessingContext source, i
                 Size = new Size(width, height),
                 Mode = ResizeMode.BoxPad,
                 Sampler = KnownResamplers.NearestNeighbor,
+                PadColor = color
             };
 
-            return color.Equals(default) ? source.Resize(options) : source.Resize(options).BackgroundColor(color);
+            return source.Resize(options);
         }
     }
 }

src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor.cs

@@ -21,19 +21,12 @@ public ResizeProcessor(ResizeOptions options, Size sourceSize)
 
             (Size size, Rectangle rectangle) = ResizeHelper.CalculateTargetLocationAndBounds(sourceSize, options);
 
-            this.Sampler = options.Sampler;
+            this.Options = options;
             this.DestinationWidth = size.Width;
             this.DestinationHeight = size.Height;
             this.DestinationRectangle = rectangle;
-            this.Compand = options.Compand;
-            this.PremultiplyAlpha = options.PremultiplyAlpha;
         }
 
-        /// <summary>
-        /// Gets the sampler to perform the resize operation.
-        /// </summary>
-        public IResampler Sampler { get; }
-
         /// <summary>
         /// Gets the destination width.
         /// </summary>
@@ -50,14 +43,9 @@ public ResizeProcessor(ResizeOptions options, Size sourceSize)
         public Rectangle DestinationRectangle { get; }
 
         /// <summary>
-        /// Gets a value indicating whether to compress or expand individual pixel color values on processing.
-        /// </summary>
-        public bool Compand { get; }
-
-        /// <summary>
-        /// Gets a value indicating whether to premultiply the alpha (if it exists) during the resize operation.
+        /// Gets the resize options.
         /// </summary>
-        public bool PremultiplyAlpha { get; }
+        public ResizeOptions Options { get; }
 
         /// <inheritdoc />
         public override ICloningImageProcessor<TPixel> CreatePixelSpecificCloningProcessor<TPixel>(Configuration configuration, Image<TPixel> source, Rectangle sourceRectangle)

src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor{TPixel}.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Advanced;
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -17,12 +16,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
     internal class ResizeProcessor<TPixel> : TransformProcessor<TPixel>, IResamplingTransformImageProcessor<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>
     {
+        private readonly ResizeOptions options;
         private readonly int destinationWidth;
         private readonly int destinationHeight;
         private readonly IResampler resampler;
         private readonly Rectangle destinationRectangle;
-        private readonly bool compand;
-        private readonly bool premultiplyAlpha;
         private Image<TPixel> destination;
 
         public ResizeProcessor(Configuration configuration, ResizeProcessor definition, Image<TPixel> source, Rectangle sourceRectangle)
@@ -31,13 +29,12 @@ public ResizeProcessor(Configuration configuration, ResizeProcessor definition,
             this.destinationWidth = definition.DestinationWidth;
             this.destinationHeight = definition.DestinationHeight;
             this.destinationRectangle = definition.DestinationRectangle;
-            this.resampler = definition.Sampler;
-            this.premultiplyAlpha = definition.PremultiplyAlpha;
-            this.compand = definition.Compand;
+            this.options = definition.Options;
+            this.resampler = definition.Options.Sampler;
         }
 
         /// <inheritdoc/>
-        protected override Size GetDestinationSize() => new Size(this.destinationWidth, this.destinationHeight);
+        protected override Size GetDestinationSize() => new(this.destinationWidth, this.destinationHeight);
 
         /// <inheritdoc/>
         protected override void BeforeImageApply(Image<TPixel> destination)
@@ -62,8 +59,11 @@ public void ApplyTransform<TResampler>(in TResampler sampler)
             Image<TPixel> destination = this.destination;
             Rectangle sourceRectangle = this.SourceRectangle;
             Rectangle destinationRectangle = this.destinationRectangle;
-            bool compand = this.compand;
-            bool premultiplyAlpha = this.premultiplyAlpha;
+            bool compand = this.options.Compand;
+            bool premultiplyAlpha = this.options.PremultiplyAlpha;
+            bool shouldFill = (this.options.Mode == ResizeMode.BoxPad || this.options.Mode == ResizeMode.Pad)
+                              && this.options.PadColor != default;
+            TPixel fillColor = this.options.PadColor.ToPixel<TPixel>();
 
             // Handle resize dimensions identical to the original
             if (source.Width == destination.Width
@@ -91,6 +91,11 @@ public void ApplyTransform<TResampler>(in TResampler sampler)
                     ImageFrame<TPixel> sourceFrame = source.Frames[i];
                     ImageFrame<TPixel> destinationFrame = destination.Frames[i];
 
+                    if (shouldFill)
+                    {
+                        destinationFrame.Clear(fillColor);
+                    }
+
                     ApplyNNResizeFrameTransform(
                         configuration,
                         sourceFrame,
@@ -123,6 +128,11 @@ public void ApplyTransform<TResampler>(in TResampler sampler)
                 ImageFrame<TPixel> sourceFrame = source.Frames[i];
                 ImageFrame<TPixel> destinationFrame = destination.Frames[i];
 
+                if (shouldFill)
+                {
+                    destinationFrame.Clear(fillColor);
+                }
+
                 ApplyResizeFrameTransform(
                     configuration,
                     sourceFrame,

src/ImageSharp/Processing/ResizeOptions.cs

@@ -51,5 +51,10 @@ public class ResizeOptions
         /// the alpha (if it exists) during the resize operation.
         /// </summary>
         public bool PremultiplyAlpha { get; set; } = true;
+
+        /// <summary>
+        /// Gets or sets the color to use as a background when padding an image.
+        /// </summary>
+        public Color PadColor { get; set; }
     }
 }

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

@@ -20,41 +20,37 @@ public class PadTest
         public void ImageShouldPad<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Pad(image.Width + 50, image.Height + 50));
-                image.DebugSave(provider);
+            using Image<TPixel> image = provider.GetImage();
+            image.Mutate(x => x.Pad(image.Width + 50, image.Height + 50));
+            image.DebugSave(provider);
 
-                // Check pixels are empty
-                for (int y = 0; y < 25; y++)
+            // Check pixels are empty
+            for (int y = 0; y < 25; y++)
+            {
+                for (int x = 0; x < 25; x++)
                 {
-                    for (int x = 0; x < 25; x++)
-                    {
-                        Assert.Equal(default, image[x, y]);
-                    }
+                    Assert.Equal(default, image[x, y]);
                 }
             }
         }
 
         [Theory]
-        [WithFileCollection(nameof(CommonTestImages), PixelTypes.Rgba32)]
+        [WithFileCollection(nameof(CommonTestImages), PixelTypes.Rgba32 | PixelTypes.Rgb24)]
         public void ImageShouldPadWithBackgroundColor<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            var color = Color.Red;
+            Color color = Color.Red;
             TPixel expected = color.ToPixel<TPixel>();
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Pad(image.Width + 50, image.Height + 50, color));
-                image.DebugSave(provider);
+            using Image<TPixel> image = provider.GetImage();
+            image.Mutate(x => x.Pad(image.Width + 50, image.Height + 50, color));
+            image.DebugSave(provider);
 
-                // Check pixels are filled
-                for (int y = 0; y < 25; y++)
+            // Check pixels are filled
+            for (int y = 0; y < 25; y++)
+            {
+                for (int x = 0; x < 25; x++)
                 {
-                    for (int x = 0; x < 25; x++)
-                    {
-                        Assert.Equal(expected, image[x, y]);
-                    }
+                    Assert.Equal(expected, image[x, y]);
                 }
             }
         }

tests/ImageSharp.Tests/Processing/Transforms/PadTest.cs

@@ -23,7 +23,7 @@ public void PadWidthHeightResizeProcessorWithCorrectOptionsSet()
 
             Assert.Equal(width, resizeProcessor.DestinationWidth);
             Assert.Equal(height, resizeProcessor.DestinationHeight);
-            Assert.Equal(sampler, resizeProcessor.Sampler);
+            Assert.Equal(sampler, resizeProcessor.Options.Sampler);
         }
     }
 }

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

@@ -35,7 +35,7 @@ public void ResizeWidthAndHeightAndSampler()
 
             Assert.Equal(width, resizeProcessor.DestinationWidth);
             Assert.Equal(height, resizeProcessor.DestinationHeight);
-            Assert.Equal(sampler, resizeProcessor.Sampler);
+            Assert.Equal(sampler, resizeProcessor.Options.Sampler);
         }
 
         [Fact]
@@ -52,8 +52,8 @@ public void ResizeWidthAndHeightAndSamplerAndCompand()
 
             Assert.Equal(width, resizeProcessor.DestinationWidth);
             Assert.Equal(height, resizeProcessor.DestinationHeight);
-            Assert.Equal(sampler, resizeProcessor.Sampler);
-            Assert.Equal(compand, resizeProcessor.Compand);
+            Assert.Equal(sampler, resizeProcessor.Options.Sampler);
+            Assert.Equal(compand, resizeProcessor.Options.Compand);
         }
 
         [Fact]
@@ -78,8 +78,8 @@ public void ResizeWithOptions()
 
             Assert.Equal(width, resizeProcessor.DestinationWidth);
             Assert.Equal(height, resizeProcessor.DestinationHeight);
-            Assert.Equal(sampler, resizeProcessor.Sampler);
-            Assert.Equal(compand, resizeProcessor.Compand);
+            Assert.Equal(sampler, resizeProcessor.Options.Sampler);
+            Assert.Equal(compand, resizeProcessor.Options.Compand);
 
             // Ensure options are not altered.
             Assert.Equal(width, resizeOptions.Size.Width);