Removed Rectangles and replaced with viewports.

Viewport now can specify an origin point.

src/DtronixPdf/Actions/RenderPageAction.cs

@@ -10,7 +10,7 @@ namespace DtronixPdf.Actions
     {
         public readonly FpdfPageT _pageInstance;
         private readonly float _scale;
-        private readonly RectangleF _viewport;
+        private readonly Viewport _viewport;
         private readonly RenderFlags _flags;
         private readonly Color? _backgroundColor;
         private readonly bool _includeAlpha;
@@ -20,7 +20,7 @@ namespace DtronixPdf.Actions
             ThreadDispatcher dispatcher,
             FpdfPageT pageInstance,
             float scale,
-            RectangleF viewport,
+            Viewport viewport,
             RenderFlags flags,
             Color? backgroundColor,
             bool includeAlpha)
@@ -38,15 +38,15 @@ namespace DtronixPdf.Actions
         {
             
             var bitmap = fpdfview.FPDFBitmapCreateEx(
-                (int)_viewport.Width,
-                (int)_viewport.Height,
+                (int)_viewport.Size.Width,
+                (int)_viewport.Size.Height,
                 (int) (_includeAlpha ? FPDFBitmapFormat.BGRA : FPDFBitmapFormat.BGR) , 
                 IntPtr.Zero, 
                 0);
 
             if(_backgroundColor.HasValue)
                 fpdfview.FPDFBitmapFillRect(
-                    bitmap, 0, 0, (int)_viewport.Width, (int)_viewport.Height, (uint) _backgroundColor.Value.ToArgb());
+                    bitmap, 0, 0, (int)_viewport.Size.Width, (int)_viewport.Size.Height, (uint) _backgroundColor.Value.ToArgb());
 
             if (bitmap == null)
                 throw new Exception("failed to create a bitmap object");
@@ -63,20 +63,38 @@ namespace DtronixPdf.Actions
                 matrix.B = 0;
                 matrix.C = 0;
                 matrix.D = _scale;
-                matrix.E = -_viewport.Left;
-                matrix.F = -_viewport.Top;
+
+                switch (_viewport.OriginLocation)
+                {
+                    case ViewportOrigin.Unset:
+                        break;
+                    case ViewportOrigin.TopLeft:
+                        matrix.E = -_viewport.Origin.X;
+                        matrix.F = -_viewport.Origin.Y;
+                        break;
+                    case ViewportOrigin.TopRight:
+                        break;
+                    case ViewportOrigin.BottomRight:
+                        break;
+                    case ViewportOrigin.BottomLeft:
+                        break;
+                    case ViewportOrigin.Center:
+                        break;
+                    default:
+                        throw new ArgumentOutOfRangeException();
+                }
 
                 clipping.Left = 0;
-                clipping.Right = _viewport.Width;
+                clipping.Right = _viewport.Size.Width;
                 clipping.Bottom = 0;
-                clipping.Top = _viewport.Height;
+                clipping.Top = _viewport.Size.Height;
 
                 fpdfview.FPDF_RenderPageBitmapWithMatrix(bitmap, _pageInstance, matrix, clipping, (int) _flags);
 
                 return new PdfBitmap(
                     bitmap,
-                    (int)_viewport.Width,
-                    (int)_viewport.Height,
+                    (int)_viewport.Size.Width,
+                    (int)_viewport.Size.Height,
                     _dispatcher,
                     _includeAlpha ? PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb,
                     _scale,

src/DtronixPdf/PdfBitmap.cs

@@ -27,10 +27,20 @@ namespace DtronixPdf
 
         public float Scale { get; }
 
-        public RectangleF Viewport { get; }
+        public Viewport Viewport { get; }
 
         public bool IsDisposed { get; private set; }
 
+        /// <summary>
+        /// Only call within the dispatcher since dll calls are made.
+        /// </summary>
+        /// <param name="pdfBitmap"></param>
+        /// <param name="width"></param>
+        /// <param name="height"></param>
+        /// <param name="dispatcher"></param>
+        /// <param name="format"></param>
+        /// <param name="scale"></param>
+        /// <param name="viewport"></param>
         internal PdfBitmap(
             FpdfBitmapT pdfBitmap, 
             int width, 
@@ -38,7 +48,7 @@ namespace DtronixPdf
             ThreadDispatcher dispatcher, 
             PixelFormat format, 
             float scale, 
-            RectangleF viewport)
+            Viewport viewport)
         {
             _pdfBitmap = pdfBitmap;
             _dispatcher = dispatcher;

src/DtronixPdf/PdfPage.cs

@@ -51,7 +51,7 @@ namespace DtronixPdf
 
             return page;
         }
-
+        /*
         public Task<PdfBitmap> Render(RenderFlags flags)
         {
             return Render(flags, 1);
@@ -67,7 +67,7 @@ namespace DtronixPdf
         {
             return Render(flags, scale, viewport, false, Color.White);
         }
-
+        
         public Task<PdfBitmap> Render(
             RenderFlags flags,
             float scale,
@@ -76,19 +76,19 @@ namespace DtronixPdf
             Color? backgroundColor)
         {
             var translatedRectangle = new RectangleF(
-                (int) ((Size.Width / 2 - viewport.Size.Width / 2 + viewport.Center.X) * scale + viewport.Size.Width / 2 * (scale - 1)),
-                (int) ((Size.Height / 2 - viewport.Size.Height / 2 - viewport.Center.Y) * scale + viewport.Size.Height / 2 * (scale - 1)),
+                (int) ((Size.Width / 2 - viewport.Size.Width / 2 + viewport.Origin.X) * scale + viewport.Size.Width / 2 * (scale - 1)),
+                (int) ((Size.Height / 2 - viewport.Size.Height / 2 - viewport.Origin.Y) * scale + viewport.Size.Height / 2 * (scale - 1)),
                 viewport.Size.Width,
                 viewport.Size.Height);
 
             return Render(flags, scale, translatedRectangle, alpha, backgroundColor);
         }
-
+        */
 
         public async Task<PdfBitmap> Render(
             RenderFlags flags,
             float scale,
-            RectangleF viewport,
+            Viewport viewport,
             bool alpha,
             Color? backgroundColor)
         {

src/DtronixPdf/Viewport.cs

@@ -1,25 +1,25 @@
-using System;
-using System.Collections.Generic;
-using System.Drawing;
-using System.Text;
+using System.Drawing;
 
 namespace DtronixPdf
 {
-    public struct Viewport
+    public readonly struct Viewport
     {
-         public readonly PointF Center;
-         public readonly SizeF Size;
+        public ViewportOrigin OriginLocation { get; }
+        public PointF Origin { get; }
+        public SizeF Size { get; }
 
-        public Viewport(PointF center, SizeF size)
+        public Viewport(PointF origin, SizeF size, ViewportOrigin originLocation)
         {
-            Center = center;
+            OriginLocation = originLocation;
+            Origin = origin;
             Size = size;
         }
 
-        public Viewport(int x, int y, int width, int height)
+        public Viewport(int x, int y, int width, int height, ViewportOrigin originLocation)
         {
-            Center = new Point(x, y);
+            OriginLocation = originLocation;
+            Origin = new Point(x, y);
             Size = new Size(width, height);
         }
     }
-}
+}

src/DtronixPdf/ViewportOrigin.cs

@@ -0,0 +1,12 @@
+namespace DtronixPdf
+{
+    public enum ViewportOrigin
+    {
+        Unset,
+        TopLeft,
+        TopRight,
+        BottomRight,
+        BottomLeft,
+        Center
+    }
+}