Create nicer wrapper of Stbi.

Quik.StbImage/StbImage.cs

@@ -0,0 +1,132 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace Quik.Stb
+{
+    /// <summary>
+    /// A class that encompasses all features of stb_image.h in a safe way.
+    /// </summary>
+    public unsafe class StbImage : IDisposable
+    {
+        private bool isDisposed = false;
+
+        /// <summary>
+        /// Pointer to the image.
+        /// </summary>
+        public IntPtr ImagePointer { get; }
+
+        /// <summary>
+        /// Width of the image.
+        /// </summary>
+        public int Width { get; }
+
+        /// <summary>
+        /// Height of the image.
+        /// </summary>
+        /// <value></value>
+        public int Height { get; }
+
+        /// <summary>
+        /// Internal image format.
+        /// </summary>
+        public StbiImageFormat Format { get; }
+        public bool IsFloat { get; }
+
+        private StbImage(IntPtr image, int x, int y, StbiImageFormat format, bool isFloat)
+        {
+            ImagePointer = image;
+            Width = x;
+            Height = y;
+            Format = format;
+            IsFloat = isFloat;
+        }
+
+        ~StbImage()
+        {
+            Dispose(false);
+        }
+
+        public void Dispose() => Dispose(true);
+
+        private void Dispose(bool disposing)
+        {
+            if (isDisposed) return;
+
+            if (disposing)
+            {
+                GC.SuppressFinalize(this);
+            }
+
+            Stbi.image_free(ImagePointer.ToPointer());
+            isDisposed = true;
+        }
+
+        /// <summary>
+        /// Set to flip the y-axis of loaded images on load.
+        /// </summary>
+        public static bool FlipVerticallyOnLoad { set => Stbi.set_flip_vertically_on_load(1); }
+
+        /// <summary>
+        /// Set to unpremultiply images on load.
+        /// </summary>
+        /// <remarks>
+        /// According to the stb_image documentation, only iPhone PNG images
+        /// can come with premultiplied alpha.
+        /// </remarks>
+        public static bool UnpremultiplyOnLoad { set => Stbi.set_unpremultiply_on_load(1); }
+
+        /// <summary>
+        /// Try loading an image, without raising exceptions.
+        /// </summary>
+        /// <param name="image">The resulting image.</param>
+        /// <param name="stream">Source stream.</param>
+        /// <param name="format">The desired image format.</param>
+        /// <returns>True on success.</returns>
+        public static bool TryLoad(out StbImage image, Stream stream, StbiImageFormat format = StbiImageFormat.Default, bool isFloat = false)
+        {
+            int x, y, iFormat;
+            StbiStreamWrapper wrapper = new StbiStreamWrapper(stream, true);
+            wrapper.CreateCallbacks(out stbi_io_callbacks cb);
+
+            stream.Position = 0;
+            IntPtr imagePtr;
+            if (isFloat)
+            {
+                imagePtr = (IntPtr)Stbi.loadf_from_callbacks(&cb, null, &x, &y, &iFormat, (int)format);
+            }
+            else
+            {
+                imagePtr = (IntPtr)Stbi.load_from_callbacks(&cb, null, &x, &y, &iFormat, (int)format);
+            }
+
+            if (imagePtr != IntPtr.Zero)
+            {
+                image = new StbImage(imagePtr, x, y, (StbiImageFormat)iFormat, isFloat);
+                return true;
+            }
+            else
+            {
+                image = null;
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// Load an image.
+        /// </summary>
+        /// <param name="stream">The stream to load from.</param>
+        /// <param name="format">The desired image format.</param>
+        /// <returns>The image object.</returns>
+        public static StbImage Load(Stream stream, StbiImageFormat format = StbiImageFormat.Default)
+        {
+            if (TryLoad(out StbImage image, stream, format))
+            {
+                return image;
+            }
+
+            string reason = Marshal.PtrToStringUTF8((IntPtr)Stbi.failure_reason());
+            throw new Exception($"Failed to load image: {reason}");
+        }
+    }
+}

Quik.StbImage/StbiImageFormat.cs

@@ -0,0 +1,11 @@
+namespace Quik.Stb
+{
+    public enum StbiImageFormat
+    {
+        Default     = (int)StbiEnum.STBI_default,
+        Grey        = (int)StbiEnum.STBI_grey,
+        GreyAlpha   = (int)StbiEnum.STBI_grey_alpha,
+        Rgb         = (int)StbiEnum.STBI_rgb,
+        Rgba        = (int)StbiEnum.STBI_rgb_alpha
+    }
+}