zxing/csharp/qrcode/detector/Detector.cs

/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using DecodeHintType = com.google.zxing.DecodeHintType;
using ReaderException = com.google.zxing.ReaderException;
using ResultPoint = com.google.zxing.ResultPoint;
using ResultPointCallback = com.google.zxing.ResultPointCallback;
using BitMatrix = com.google.zxing.common.BitMatrix;
using DetectorResult = com.google.zxing.common.DetectorResult;
using GridSampler = com.google.zxing.common.GridSampler;
using PerspectiveTransform = com.google.zxing.common.PerspectiveTransform;
using Version = com.google.zxing.qrcode.decoder.Version;
namespace com.google.zxing.qrcode.detector
{
	
	/// <summary> <p>Encapsulates logic that can detect a QR Code in an image, even if the QR Code
	/// is rotated or skewed, or partially obscured.</p>
	/// 
	/// </summary>
	/// <author>  Sean Owen
	/// </author>
	/// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source 
	/// </author>
	public class Detector
	{
		virtual protected internal BitMatrix Image
		{
			get
			{
				return image;
			}
			
		}
		virtual protected internal ResultPointCallback ResultPointCallback
		{
			get
			{
				return resultPointCallback;
			}
			
		}
		
		//UPGRADE_NOTE: Final was removed from the declaration of 'image '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"
		private BitMatrix image;
		private ResultPointCallback resultPointCallback;
		
		public Detector(BitMatrix image)
		{
			this.image = image;
		}
		
		/// <summary> <p>Detects a QR Code in an image, simply.</p>
		/// 
		/// </summary>
		/// <returns> {@link DetectorResult} encapsulating results of detecting a QR Code
		/// </returns>
		/// <throws>  ReaderException if no QR Code can be found </throws>
		public virtual DetectorResult detect()
		{
			return detect(null);
		}
		
		/// <summary> <p>Detects a QR Code in an image, simply.</p>
		/// 
		/// </summary>
		/// <param name="hints">optional hints to detector
		/// </param>
		/// <returns> {@link DetectorResult} encapsulating results of detecting a QR Code
		/// </returns>
		/// <throws>  ReaderException if no QR Code can be found </throws>
		public virtual DetectorResult detect(System.Collections.Hashtable hints)
		{
			
			resultPointCallback = hints == null?null:(ResultPointCallback) hints[DecodeHintType.NEED_RESULT_POINT_CALLBACK];
			
			FinderPatternFinder finder = new FinderPatternFinder(image, resultPointCallback);
			FinderPatternInfo info = finder.find(hints);
			
			return processFinderPatternInfo(info);
		}
		
		protected internal virtual DetectorResult processFinderPatternInfo(FinderPatternInfo info)
		{
			
			FinderPattern topLeft = info.TopLeft;
			FinderPattern topRight = info.TopRight;
			FinderPattern bottomLeft = info.BottomLeft;
			
			float moduleSize = calculateModuleSize(topLeft, topRight, bottomLeft);
			if (moduleSize < 1.0f)
			{
				throw ReaderException.Instance;
			}
			int dimension = computeDimension(topLeft, topRight, bottomLeft, moduleSize);
			Version provisionalVersion = Version.getProvisionalVersionForDimension(dimension);
			int modulesBetweenFPCenters = provisionalVersion.DimensionForVersion - 7;
			
			AlignmentPattern alignmentPattern = null;
			// Anything above version 1 has an alignment pattern
			if (provisionalVersion.AlignmentPatternCenters.Length > 0)
			{
				
				// Guess where a "bottom right" finder pattern would have been
				float bottomRightX = topRight.X - topLeft.X + bottomLeft.X;
				float bottomRightY = topRight.Y - topLeft.Y + bottomLeft.Y;
				
				// Estimate that alignment pattern is closer by 3 modules
				// from "bottom right" to known top left location
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				float correctionToTopLeft = 1.0f - 3.0f / (float) modulesBetweenFPCenters;
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				int estAlignmentX = (int) (topLeft.X + correctionToTopLeft * (bottomRightX - topLeft.X));
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				int estAlignmentY = (int) (topLeft.Y + correctionToTopLeft * (bottomRightY - topLeft.Y));
				
				// Kind of arbitrary -- expand search radius before giving up
				for (int i = 4; i <= 16; i <<= 1)
				{
					try
					{
						//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
						alignmentPattern = findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY, (float) i);
						break;
					}
					catch (ReaderException)
					{
						// try next round
					}
				}
				// If we didn't find alignment pattern... well try anyway without it
			}
			
			PerspectiveTransform transform = createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
			
			BitMatrix bits = sampleGrid(image, transform, dimension);
			
			ResultPoint[] points;
			if (alignmentPattern == null)
			{
				points = new ResultPoint[]{bottomLeft, topLeft, topRight};
			}
			else
			{
				points = new ResultPoint[]{bottomLeft, topLeft, topRight, alignmentPattern};
			}
			return new DetectorResult(bits, points);
		}
		
		public virtual PerspectiveTransform createTransform(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, ResultPoint alignmentPattern, int dimension)
		{
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			float dimMinusThree = (float) dimension - 3.5f;
			float bottomRightX;
			float bottomRightY;
			float sourceBottomRightX;
			float sourceBottomRightY;
			if (alignmentPattern != null)
			{
				bottomRightX = alignmentPattern.X;
				bottomRightY = alignmentPattern.Y;
				sourceBottomRightX = sourceBottomRightY = dimMinusThree - 3.0f;
			}
			else
			{
				// Don't have an alignment pattern, just make up the bottom-right point
				bottomRightX = (topRight.X - topLeft.X) + bottomLeft.X;
				bottomRightY = (topRight.Y - topLeft.Y) + bottomLeft.Y;
				sourceBottomRightX = sourceBottomRightY = dimMinusThree;
			}
			
			PerspectiveTransform transform = PerspectiveTransform.quadrilateralToQuadrilateral(3.5f, 3.5f, dimMinusThree, 3.5f, sourceBottomRightX, sourceBottomRightY, 3.5f, dimMinusThree, topLeft.X, topLeft.Y, topRight.X, topRight.Y, bottomRightX, bottomRightY, bottomLeft.X, bottomLeft.Y);
			
			return transform;
		}
		
		private static BitMatrix sampleGrid(BitMatrix image, PerspectiveTransform transform, int dimension)
		{
			
			GridSampler sampler = GridSampler.Instance;
			return sampler.sampleGrid(image, dimension, transform);
		}
		
		/// <summary> <p>Computes the dimension (number of modules on a size) of the QR Code based on the position
		/// of the finder patterns and estimated module size.</p>
		/// </summary>
		protected internal static int computeDimension(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft, float moduleSize)
		{
			int tltrCentersDimension = round(ResultPoint.distance(topLeft, topRight) / moduleSize);
			int tlblCentersDimension = round(ResultPoint.distance(topLeft, bottomLeft) / moduleSize);
			int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
			switch (dimension & 0x03)
			{
				
				// mod 4
				case 0: 
					dimension++;
					break;
					// 1? do nothing
				
				case 2: 
					dimension--;
					break;
				
				case 3: 
					throw ReaderException.Instance;
				}
			return dimension;
		}
		
		/// <summary> <p>Computes an average estimated module size based on estimated derived from the positions
		/// of the three finder patterns.</p>
		/// </summary>
		protected internal virtual float calculateModuleSize(ResultPoint topLeft, ResultPoint topRight, ResultPoint bottomLeft)
		{
			// Take the average
			return (calculateModuleSizeOneWay(topLeft, topRight) + calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
		}
		
		/// <summary> <p>Estimates module size based on two finder patterns -- it uses
		/// {@link #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)} to figure the
		/// width of each, measuring along the axis between their centers.</p>
		/// </summary>
		private float calculateModuleSizeOneWay(ResultPoint pattern, ResultPoint otherPattern)
		{
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int) pattern.X, (int) pattern.Y, (int) otherPattern.X, (int) otherPattern.Y);
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int) otherPattern.X, (int) otherPattern.Y, (int) pattern.X, (int) pattern.Y);
			if (System.Single.IsNaN(moduleSizeEst1))
			{
				return moduleSizeEst2 / 7.0f;
			}
			if (System.Single.IsNaN(moduleSizeEst2))
			{
				return moduleSizeEst1 / 7.0f;
			}
			// Average them, and divide by 7 since we've counted the width of 3 black modules,
			// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
			return (moduleSizeEst1 + moduleSizeEst2) / 14.0f;
		}
		
		/// <summary> See {@link #sizeOfBlackWhiteBlackRun(int, int, int, int)}; computes the total width of
		/// a finder pattern by looking for a black-white-black run from the center in the direction
		/// of another point (another finder pattern center), and in the opposite direction too.</p>
		/// </summary>
		private float sizeOfBlackWhiteBlackRunBothWays(int fromX, int fromY, int toX, int toY)
		{
			
			float result = sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
			
			// Now count other way -- don't run off image though of course
			float scale = 1.0f;
			int otherToX = fromX - (toX - fromX);
			if (otherToX < 0)
			{
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				scale = (float) fromX / (float) (fromX - otherToX);
				otherToX = 0;
			}
			else if (otherToX >= image.Width)
			{
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				scale = (float) (image.Width - 1 - fromX) / (float) (otherToX - fromX);
				otherToX = image.Width - 1;
			}
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			int otherToY = (int) (fromY - (toY - fromY) * scale);
			
			scale = 1.0f;
			if (otherToY < 0)
			{
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				scale = (float) fromY / (float) (fromY - otherToY);
				otherToY = 0;
			}
			else if (otherToY >= image.Height)
			{
				//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
				scale = (float) (image.Height - 1 - fromY) / (float) (otherToY - fromY);
				otherToY = image.Height - 1;
			}
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			otherToX = (int) (fromX + (otherToX - fromX) * scale);
			
			result += sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
			return result - 1.0f; // -1 because we counted the middle pixel twice
		}
		
		/// <summary> <p>This method traces a line from a point in the image, in the direction towards another point.
		/// It begins in a black region, and keeps going until it finds white, then black, then white again.
		/// It reports the distance from the start to this point.</p>
		/// 
		/// <p>This is used when figuring out how wide a finder pattern is, when the finder pattern
		/// may be skewed or rotated.</p>
		/// </summary>
		private float sizeOfBlackWhiteBlackRun(int fromX, int fromY, int toX, int toY)
		{
			// Mild variant of Bresenham's algorithm;
			// see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
			bool steep = System.Math.Abs(toY - fromY) > System.Math.Abs(toX - fromX);
			if (steep)
			{
				int temp = fromX;
				fromX = fromY;
				fromY = temp;
				temp = toX;
				toX = toY;
				toY = temp;
			}
			
			int dx = System.Math.Abs(toX - fromX);
			int dy = System.Math.Abs(toY - fromY);
			int error = - dx >> 1;
			int ystep = fromY < toY?1:- 1;
			int xstep = fromX < toX?1:- 1;
			int state = 0; // In black pixels, looking for white, first or second time
			for (int x = fromX, y = fromY; x != toX; x += xstep)
			{
				
				int realX = steep?y:x;
				int realY = steep?x:y;
				if (state == 1)
				{
					// In white pixels, looking for black
					if (image.get_Renamed(realX, realY))
					{
						state++;
					}
				}
				else
				{
					if (!image.get_Renamed(realX, realY))
					{
						state++;
					}
				}
				
				if (state == 3)
				{
					// Found black, white, black, and stumbled back onto white; done
					int diffX = x - fromX;
					int diffY = y - fromY;
					//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
					return (float) System.Math.Sqrt((double) (diffX * diffX + diffY * diffY));
				}
				error += dy;
				if (error > 0)
				{
					if (y == toY)
					{
						break;
					}
					y += ystep;
					error -= dx;
				}
			}
			int diffX2 = toX - fromX;
			int diffY2 = toY - fromY;
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			return (float) System.Math.Sqrt((double) (diffX2 * diffX2 + diffY2 * diffY2));
		}
		
		/// <summary> <p>Attempts to locate an alignment pattern in a limited region of the image, which is
		/// guessed to contain it. This method uses {@link AlignmentPattern}.</p>
		/// 
		/// </summary>
		/// <param name="overallEstModuleSize">estimated module size so far
		/// </param>
		/// <param name="estAlignmentX">x coordinate of center of area probably containing alignment pattern
		/// </param>
		/// <param name="estAlignmentY">y coordinate of above
		/// </param>
		/// <param name="allowanceFactor">number of pixels in all directions to search from the center
		/// </param>
		/// <returns> {@link AlignmentPattern} if found, or null otherwise
		/// </returns>
		/// <throws>  ReaderException if an unexpected error occurs during detection </throws>
		protected internal virtual AlignmentPattern findAlignmentInRegion(float overallEstModuleSize, int estAlignmentX, int estAlignmentY, float allowanceFactor)
		{
			// Look for an alignment pattern (3 modules in size) around where it
			// should be
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			int allowance = (int) (allowanceFactor * overallEstModuleSize);
			int alignmentAreaLeftX = System.Math.Max(0, estAlignmentX - allowance);
			int alignmentAreaRightX = System.Math.Min(image.Width - 1, estAlignmentX + allowance);
			if (alignmentAreaRightX - alignmentAreaLeftX < overallEstModuleSize * 3)
			{
				throw ReaderException.Instance;
			}
			
			int alignmentAreaTopY = System.Math.Max(0, estAlignmentY - allowance);
			int alignmentAreaBottomY = System.Math.Min(image.Height - 1, estAlignmentY + allowance);
			
			AlignmentPatternFinder alignmentFinder = new AlignmentPatternFinder(image, alignmentAreaLeftX, alignmentAreaTopY, alignmentAreaRightX - alignmentAreaLeftX, alignmentAreaBottomY - alignmentAreaTopY, overallEstModuleSize, resultPointCallback);
			return alignmentFinder.find();
		}
		
		/// <summary> Ends up being a bit faster than Math.round(). This merely rounds its argument to the nearest int,
		/// where x.5 rounds up.
		/// </summary>
		private static int round(float d)
		{
			//UPGRADE_WARNING: Data types in Visual C# might be different.  Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
			return (int) (d + 0.5f);
		}
	}
}