Allow changing the current region of interest without having to reloa…

…d the entire image.

src/Tesseract.Tests/EngineTests.cs

@@ -52,6 +52,31 @@ public void CanParseText()
                 }
             }
         }
+
+		[Test]
+		public void CanParseDifferentRegionsInSameImage()
+		{
+			using (var engine = new TesseractEngine(@"./tessdata", "eng", EngineMode.Default)) {
+				using(var img = Pix.LoadFromFile("./phototest.tif")) {
+					using(var page = engine.Process(img, Rect.FromCoords(0, 0, img.Width, 188))) {
+						var region1Text = page.GetText();
+
+						const string expectedTextRegion1 =
+							"This is a lot of 12 point text to test the\nocr code and see if it works on all types\nof file format.\n\n";
+
+						Assert.That(region1Text, Is.EqualTo(expectedTextRegion1));
+
+						page.RegionOfInterest =  Rect.FromCoords(0, 188, img.Width, img.Height);
+
+						var region2Text = page.GetText();
+						const string expectedTextRegion2 =
+							"The quick brown dog jumped over the\nlazy fox. The quick brown dog jumped\nover the lazy fox. The quick brown dog\njumped over the lazy fox. The quick\nbrown dog jumped over the lazy fox.\n\n";
+
+						Assert.That(region2Text, Is.EqualTo(expectedTextRegion2));
+					}
+				}
+			}
+		}
 
         [Test]
         public void CanParseUznFile()

src/Tesseract/Page.cs

@@ -9,14 +9,41 @@ namespace Tesseract
     public sealed class Page : DisposableBase
     {
         private bool runRecognitionPhase;
-
+		private Rect regionOfInterest;
+
+
         public TesseractEngine Engine { get; private set; }
+		public Pix Image { get; private set; }
 
-        internal Page(TesseractEngine engine)
+        internal Page(TesseractEngine engine, Pix image, Rect regionOfInterest)
         {
             Engine = engine;
+			Image = image;
+			RegionOfInterest = regionOfInterest;
         }
-
+
+		/// <summary>
+		/// The current region of interest being parsed.
+		/// </summary>
+		public Rect RegionOfInterest {
+			get {
+				return regionOfInterest;
+			}
+			set {
+				if (value.X1 < 0 || value.Y1 < 0 || value.X2 > Image.Width || value.Y2 > Image.Height)
+                	throw new ArgumentException("The region of interest to be processed must be within the image bounds.", "value");
+
+				if(regionOfInterest != value) {					
+					regionOfInterest = value;
+
+					// update region of interest in image
+					Interop.TessApi.BaseApiSetRectangle(Engine.Handle, regionOfInterest.X1, regionOfInterest.Y1, regionOfInterest.Width, regionOfInterest.Height);
+
+					// request rerun of recognition on the next call that requires recognition
+					runRecognitionPhase = true;
+				}
+			}
+		}
 
         public PageIterator AnalyseLayout()
         {

src/Tesseract/TesseractEngine.cs

@@ -187,7 +187,7 @@ public Page Process(Pix image, PageSegMode? pageSegMode = null)
         /// <returns>A result iterator</returns>
         public Page Process(Pix image, Rect region, PageSegMode? pageSegMode = null)
         {        	
-            return Process(image, null, new Rect(0, 0, image.Width, image.Height), pageSegMode);
+            return Process(image, null, region, pageSegMode);
         }
 
 
@@ -227,11 +227,10 @@ public Page Process(Pix image, string inputName, Rect region, PageSegMode? pageS
 
             Interop.TessApi.BaseAPISetPageSegMode(handle, pageSegMode.HasValue ? pageSegMode.Value : DefaultPageSegMode);
             Interop.TessApi.BaseApiSetImage(handle, image.Handle);
-            Interop.TessApi.BaseApiSetRectangle(handle, region.X1, region.Y1, region.Width, region.Height);
             if(!String.IsNullOrEmpty(inputName)) {
             	Interop.TessApi.BaseApiSetInputName(handle, inputName);
             }
-            var page = new Page(this);
+            var page = new Page(this, image, region);
             page.Disposed += OnIteratorDisposed;
             return page;
         }