From 0889318c57ebe215f341da1fa01cdd12d39856d5 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <dan@walms.co.uk>
Date: Sat, 9 May 2020 16:28:32 -0300
Subject: [PATCH] Add createscaled bitmap

---
 src/Avalonia.Visuals/Media/Imaging/Bitmap.cs       |  6 ++++++
 .../Platform/IPlatformRenderInterface.cs           |  2 ++
 src/Skia/Avalonia.Skia/ImmutableBitmap.cs          | 14 ++++++++++++++
 src/Skia/Avalonia.Skia/PlatformRenderInterface.cs  | 12 ++++++++++++
 .../Avalonia.Direct2D1/Direct2D1Platform.cs        |  5 +++++
 5 files changed, 39 insertions(+)

diff --git a/src/Avalonia.Visuals/Media/Imaging/Bitmap.cs b/src/Avalonia.Visuals/Media/Imaging/Bitmap.cs
index e276b7f65d..3d567fe458 100644
--- a/src/Avalonia.Visuals/Media/Imaging/Bitmap.cs
+++ b/src/Avalonia.Visuals/Media/Imaging/Bitmap.cs
@@ -23,6 +23,12 @@ namespace Avalonia.Media.Imaging
             return new Bitmap(factory.LoadBitmapToHeight(stream, height, interpolationMode));
         }
 
+        public static Bitmap CreateScaledBitmap(Bitmap src, PixelSize destinationSize, BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality)
+        {
+            IPlatformRenderInterface factory = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
+            return new Bitmap(factory.ResizeBitmap(src.PlatformImpl.Item, destinationSize, interpolationMode));
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Bitmap"/> class.
         /// </summary>
diff --git a/src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs b/src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs
index 381dde4891..e35d1154a1 100644
--- a/src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs
+++ b/src/Avalonia.Visuals/Platform/IPlatformRenderInterface.cs
@@ -114,6 +114,8 @@ namespace Avalonia.Platform
         /// <returns>An <see cref="IBitmapImpl"/>.</returns>
         IBitmapImpl LoadBitmapToHeight(Stream stream, int height, BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality);
 
+        IBitmapImpl ResizeBitmap(IBitmapImpl bitmapImpl, PixelSize destinationSize, BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality);
+
         /// <summary>
         /// Loads a bitmap implementation from a pixels in memory.
         /// </summary>
diff --git a/src/Skia/Avalonia.Skia/ImmutableBitmap.cs b/src/Skia/Avalonia.Skia/ImmutableBitmap.cs
index 887d023917..8323eabfbb 100644
--- a/src/Skia/Avalonia.Skia/ImmutableBitmap.cs
+++ b/src/Skia/Avalonia.Skia/ImmutableBitmap.cs
@@ -40,6 +40,20 @@ namespace Avalonia.Skia
             }
         }
 
+        public ImmutableBitmap(ImmutableBitmap src, PixelSize destinationSize, BitmapInterpolationMode interpolationMode)
+        {            
+            SKImageInfo info = new SKImageInfo(destinationSize.Width, destinationSize.Height, SKColorType.Bgra8888);
+            SKImage output = SKImage.Create(info);
+            src._image.ScalePixels(output.PeekPixels(), interpolationMode.ToSKFilterQuality());
+
+            _image = output;
+
+            PixelSize = new PixelSize(_image.Width, _image.Height);
+
+            // TODO: Skia doesn't have an API for DPI.
+            Dpi = new Vector(96, 96);
+        }
+
         // NOTE, putting the stream before options in the parameters, causes an exception
         // inside SKCodec.Create with optimized code. Probably a bug in .net compiler.
         // Other option is to have the argument order as desired and use PreserveSig options.
diff --git a/src/Skia/Avalonia.Skia/PlatformRenderInterface.cs b/src/Skia/Avalonia.Skia/PlatformRenderInterface.cs
index 32fee417a4..f744b2f00a 100644
--- a/src/Skia/Avalonia.Skia/PlatformRenderInterface.cs
+++ b/src/Skia/Avalonia.Skia/PlatformRenderInterface.cs
@@ -109,6 +109,18 @@ namespace Avalonia.Skia
             return new ImmutableBitmap(size, dpi, stride, format, data);
         }
 
+        public IBitmapImpl ResizeBitmap(IBitmapImpl bitmapImpl, PixelSize destinationSize, BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality)
+        {
+            if (bitmapImpl is ImmutableBitmap ibmp)
+            {
+                return new ImmutableBitmap(ibmp, destinationSize, interpolationMode);
+            }
+            else
+            {
+                throw new Exception("Invalid source bitmap type.");
+            }
+        }
+
         /// <inheritdoc />
         public IRenderTargetBitmapImpl CreateRenderTargetBitmap(PixelSize size, Vector dpi)
         {
diff --git a/src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs b/src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs
index fd6c2dffd5..ef5b3255c1 100644
--- a/src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs
+++ b/src/Windows/Avalonia.Direct2D1/Direct2D1Platform.cs
@@ -201,6 +201,11 @@ namespace Avalonia.Direct2D1
             throw new NotImplementedException();
         }
 
+        public IBitmapImpl ResizeBitmap(IBitmapImpl bitmapImpl, PixelSize destinationSize, BitmapInterpolationMode interpolationMode = BitmapInterpolationMode.HighQuality)
+        {
+            throw new NotImplementedException();
+        }
+
         public IBitmapImpl LoadBitmap(PixelFormat format, IntPtr data, PixelSize size, Vector dpi, int stride)
         {
             return new WicBitmapImpl(format, data, size, dpi, stride);