vendoring NetVips

vendor/NetVips/Region.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Runtime.InteropServices;
+using NetVips.Internal;
+
+namespace NetVips;
+
+/// <summary>
+/// Wrap a <see cref="VipsRegion"/> object.
+/// </summary>
+/// <remarks>
+/// A region is a small part of an image. You use regions to read pixels
+/// out of images without storing the entire image in memory.
+/// At least libvips 8.8 is needed.
+/// </remarks>
+public class Region : VipsObject
+{
+    private Region(nint pointer) : base(pointer)
+    {
+    }
+
+    /// <summary>
+    /// Make a region on an image.
+    /// </summary>
+    /// <param name="image"><see cref="Image"/> to create this region on.</param>
+    /// <returns>A new <see cref="Region"/>.</returns>
+    /// <exception cref="VipsException">If unable to make a new region on <paramref name="image"/>.</exception>
+    public static Region New(Image image)
+    {
+        var vi = VipsRegion.New(image);
+        if (vi == IntPtr.Zero)
+        {
+            throw new VipsException("unable to make region");
+        }
+
+        return new Region(vi);
+    }
+
+    /// <summary>
+    /// Width of pixels held by region.
+    /// </summary>
+    public int Width => VipsRegion.Width(this);
+
+    /// <summary>
+    /// Height of pixels held by region.
+    /// </summary>
+    public int Height => VipsRegion.Height(this);
+
+    /// <summary>
+    /// Fetch an area of pixels.
+    /// </summary>
+    /// <param name="left">Left edge of area to fetch.</param>
+    /// <param name="top">Top edge of area to fetch.</param>
+    /// <param name="width">Width of area to fetch.</param>
+    /// <param name="height">Height of area to fetch.</param>
+    /// <returns>An array of bytes filled with pixel data.</returns>
+    public byte[] Fetch(int left, int top, int width, int height)
+    {
+        var pointer = VipsRegion.Fetch(this, left, top, width, height, out var size);
+        if (pointer == IntPtr.Zero)
+        {
+            throw new VipsException("unable to fetch from region");
+        }
+
+        var managedArray = new byte[size];
+        Marshal.Copy(pointer, managedArray, 0, (int)size);
+
+        GLib.GFree(pointer);
+
+        return managedArray;
+    }
+}