Vanara/PInvoke/Gdi32/GdiObjExtensions.cs

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using Vanara.Extensions;
using static Vanara.PInvoke.Gdi32;

namespace Vanara.PInvoke
{
	/// <summary>Extension methods to convert GdiObj handle variants to their .NET equivalents.</summary>
	public static class GdiObjExtensions
	{
		/// <summary>Draws on a device context (<see cref="Graphics"/>) via a DIB section. This is useful when you need to draw on a transparent background.</summary>
		/// <param name="dc">The device context.</param>
		/// <param name="bounds">The bounds of the device context to paint.</param>
		/// <param name="drawMethod">The draw method.</param>
		public static void DrawViaDIB(this IDeviceContext dc, in Rectangle bounds, Action<SafeHDC, Rectangle> drawMethod)
		{
			using (var sdc = new SafeHDC(dc))
				DrawViaDIB(sdc, bounds, drawMethod);
		}

		/// <summary>Draws on a device context (<see cref="SafeHDC"/>) via a DIB section. This is useful when you need to draw on a transparent background.</summary>
		/// <param name="hdc">The device context.</param>
		/// <param name="bounds">The bounds of the device context to paint.</param>
		/// <param name="drawMethod">The draw method.</param>
		public static void DrawViaDIB(this SafeHDC hdc, in Rectangle bounds, Action<SafeHDC, Rectangle> drawMethod)
		{
			// Create a memory DC so we can work off screen
			using (var memoryHdc = hdc.GetCompatibleDCHandle())
			{
				// Create a device-independent bitmap and select it into our DC
				var info = new BITMAPINFO(bounds.Width, -bounds.Height);
				using (memoryHdc.SelectObject(CreateDIBSection(hdc, ref info, 0, out var pBits, IntPtr.Zero, 0)))
				{
					// Call method
					drawMethod(memoryHdc, bounds);

					// Copy to foreground
					BitBlt(hdc, bounds.Left, bounds.Top, bounds.Width, bounds.Height, memoryHdc, 0, 0, RasterOperationMode.SRCCOPY);
				}
			}
		}

		/// <summary>Creates a <see cref="Bitmap"/> from an <see cref="HBITMAP"/>.</summary>
		/// <param name="hbmp">The HBMP value.</param>
		/// <returns>The Bitmap instance.</returns>
		public static Bitmap ToBitmap(this in HBITMAP hbmp) => hbmp.IsNull ? null : Image.FromHbitmap((IntPtr)hbmp);

		/// <summary>Creates a <see cref="Bitmap"/> from a <see cref="SafeHBITMAP"/>.</summary>
		/// <param name="hbmp">The HBMP value.</param>
		/// <returns>The Bitmap instance.</returns>
		public static Bitmap ToBitmap(this SafeHBITMAP hbmp) => ((HBITMAP)hbmp).ToBitmap();

		/// <summary>Creates a managed <see cref="System.Drawing.Brush"/> from this HBRUSH instance.</summary>
		/// <param name="hbr">The HBRUSH value.</param>
		/// <returns>A managed brush instance.</returns>
		public static Brush ToBrush(this in HBRUSH hbr) => hbr.IsNull ? null : new NativeBrush(hbr);

		/// <summary>Creates a managed <see cref="System.Drawing.Brush"/> from this HBRUSH instance.</summary>
		/// <param name="hbr">The HBRUSH value.</param>
		/// <returns>A managed brush instance.</returns>
		public static Brush ToBrush(this SafeHBRUSH hbr) => ((HBRUSH)hbr).ToBrush();

		/// <summary>Creates a <see cref="Font"/> from an <see cref="HFONT"/>.</summary>
		/// <param name="hf">The HFONT value.</param>
		/// <returns>The Font instance.</returns>
		public static Font ToFont(this in HFONT hf) => hf.IsNull ? null : Font.FromHfont((IntPtr)hf);

		/// <summary>Creates a <see cref="Font"/> from an <see cref="HFONT"/>.</summary>
		/// <param name="hf">The HFONT value.</param>
		/// <returns>The Font instance.</returns>
		public static Font ToFont(this SafeHFONT hf) => ((HFONT)hf).ToFont();

		/// <summary>Creates a <see cref="Pen"/> from an <see cref="HPEN"/>.</summary>
		/// <param name="hpen">The HPEN value.</param>
		/// <returns>The Pen instance.</returns>
		public static Pen ToPen(this in HPEN hpen)
		{
			using (var ptr = GetObject(hpen))
			{
				var lpen = ptr.ToStructure<EXTLOGPEN>();
				Pen pen = null;
				switch (lpen.elpBrushStyle)
				{
					case BrushStyle.BS_DIBPATTERN:
					case BrushStyle.BS_DIBPATTERNPT:
						var lw = (DIBColorMode)(uint)lpen.elpColor;
						var hb = CreateDIBPatternBrushPt(lpen.elpHatch, lw);
						pen = new Pen(((HBRUSH)hb).ToBrush());
						break;

					case BrushStyle.BS_HATCHED:
						var hbr = new HatchBrush((System.Drawing.Drawing2D.HatchStyle)lpen.elpHatch.ToInt32(), lpen.elpColor);
						pen = new Pen(hbr);
						break;

					case BrushStyle.BS_PATTERN:
						var pbr = new TextureBrush(Image.FromHbitmap(lpen.elpHatch));
						pen = new Pen(pbr);
						break;

					case BrushStyle.BS_HOLLOW:
					case BrushStyle.BS_SOLID:
					default:
						pen = new Pen(lpen.elpColor) { DashStyle = (DashStyle)lpen.Style };
						if (pen.DashStyle == DashStyle.Custom && lpen.elpNumEntries > 0)
						{
							var styleArray = lpen.elpStyleEntry.ToArray<uint>((int)lpen.elpNumEntries);
							pen.DashPattern = Array.ConvertAll(styleArray, i => (float)i);
						}
						break;
				}
				if (lpen.Type == Gdi32.PenType.PS_GEOMETRIC)
				{
					pen.LineJoin = lpen.Join == PenJoin.PS_JOIN_MITER ? LineJoin.Miter : (lpen.Join == PenJoin.PS_JOIN_BEVEL ? LineJoin.Bevel : LineJoin.Round);
					pen.EndCap = pen.StartCap = lpen.EndCap == PenEndCap.PS_ENDCAP_FLAT ? LineCap.Flat : (lpen.EndCap == PenEndCap.PS_ENDCAP_SQUARE ? LineCap.Square : LineCap.Round);
					pen.Width = LogicalWidthToDeviceWidth((int)lpen.elpWidth);
				}
				else
				{
					pen.Width = lpen.elpWidth;
				}
				return pen;
			}
		}

		/// <summary>Creates a <see cref="Pen"/> from an <see cref="HPEN"/>.</summary>
		/// <param name="hpen">The HPEN value.</param>
		/// <returns>The Pen instance.</returns>
		public static Pen ToPen(this SafeHPEN hpen) => ((HPEN)hpen).ToPen();

		/// <summary>Creates a <see cref="Region"/> from an <see cref="HRGN"/>.</summary>
		/// <param name="hrgn">The HRGN value.</param>
		/// <returns>The Region instance.</returns>
		public static Region ToRegion(this in HRGN hrgn) => hrgn.IsNull ? null : Region.FromHrgn((IntPtr)hrgn);

		/// <summary>Creates a <see cref="Region"/> from an <see cref="HRGN"/>.</summary>
		/// <param name="hrgn">The HRGN value.</param>
		/// <returns>The Region instance.</returns>
		public static Region ToRegion(this SafeHRGN hrgn) => ((HRGN)hrgn).ToRegion();

		private class NativeBrush : Brush
		{
			public NativeBrush(HBRUSH hBrush)
			{
				var lb = GetObject<LOGBRUSH>(hBrush);
				var b2 = CreateBrushIndirect(lb);
				SetNativeBrush(b2.DangerousGetHandle());
				b2.SetHandleAsInvalid();
			}

			public override object Clone() => this;
		}
	}
}