zxing/csharp/LuminanceSource.cs

using System.Text;

/*
 * Copyright 2009 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.
 */

namespace com.google.zxing
{

	/// <summary>
	/// The purpose of this class hierarchy is to abstract different bitmap implementations across
	/// platforms into a standard interface for requesting greyscale luminance values. The interface
	/// only provides immutable methods; therefore crop and rotation create copies. This is to ensure
	/// that one Reader does not modify the original luminance source and leave it in an unknown state
	/// for other Readers in the chain.
	/// 
	/// @author dswitkin@google.com (Daniel Switkin)
	/// </summary>
	public abstract class LuminanceSource
	{

	  private readonly int width;
	  private readonly int height;

	  protected internal LuminanceSource(int width, int height)
	  {
		this.width = width;
		this.height = height;
	  }

	  /// <summary>
	  /// Fetches one row of luminance data from the underlying platform's bitmap. Values range from
	  /// 0 (black) to 255 (white). Because Java does not have an unsigned byte type, callers will have
	  /// to bitwise and with 0xff for each value. It is preferable for implementations of this method
	  /// to only fetch this row rather than the whole image, since no 2D Readers may be installed and
	  /// getMatrix() may never be called.
	  /// </summary>
	  /// <param name="y"> The row to fetch, 0 <= y < getHeight(). </param>
	  /// <param name="row"> An optional preallocated array. If null or too small, it will be ignored.
	  ///            Always use the returned object, and ignore the .length of the array. </param>
	  /// <returns> An array containing the luminance data. </returns>
	  public abstract sbyte[] getRow(int y, sbyte[] row);

	  /// <summary>
	  /// Fetches luminance data for the underlying bitmap. Values should be fetched using:
	  /// int luminance = array[y * width + x] & 0xff;
	  /// </summary>
	  /// <returns> A row-major 2D array of luminance values. Do not use result.length as it may be
	  ///         larger than width * height bytes on some platforms. Do not modify the contents
	  ///         of the result. </returns>
	  public abstract sbyte[] Matrix {get;}

	  /// <returns> The width of the bitmap. </returns>
	  public int Width
	  {
		  get
		  {
			return width;
		  }
	  }

	  /// <returns> The height of the bitmap. </returns>
	  public int Height
	  {
		  get
		  {
			return height;
		  }
	  }

	  /// <returns> Whether this subclass supports cropping. </returns>
	  public virtual bool CropSupported
	  {
		  get
		  {
			return false;
		  }
	  }

	  /// <summary>
	  /// Returns a new object with cropped image data. Implementations may keep a reference to the
	  /// original data rather than a copy. Only callable if isCropSupported() is true.
	  /// </summary>
	  /// <param name="left"> The left coordinate, 0 <= left < getWidth(). </param>
	  /// <param name="top"> The top coordinate, 0 <= top <= getHeight(). </param>
	  /// <param name="width"> The width of the rectangle to crop. </param>
	  /// <param name="height"> The height of the rectangle to crop. </param>
	  /// <returns> A cropped version of this object. </returns>
	  public virtual LuminanceSource crop(int left, int top, int width, int height)
	  {
		throw new System.NotSupportedException("This luminance source does not support cropping.");
	  }

	  /// <returns> Whether this subclass supports counter-clockwise rotation. </returns>
	  public virtual bool RotateSupported
	  {
		  get
		  {
			return false;
		  }
	  }

	  /// <summary>
	  /// Returns a new object with rotated image data by 90 degrees counterclockwise.
	  /// Only callable if <seealso cref="#isRotateSupported()"/> is true.
	  /// </summary>
	  /// <returns> A rotated version of this object. </returns>
	  public virtual LuminanceSource rotateCounterClockwise()
	  {
		throw new System.NotSupportedException("This luminance source does not support rotation by 90 degrees.");
	  }

	  /// <summary>
	  /// Returns a new object with rotated image data by 45 degrees counterclockwise.
	  /// Only callable if <seealso cref="#isRotateSupported()"/> is true.
	  /// </summary>
	  /// <returns> A rotated version of this object. </returns>
	  public virtual LuminanceSource rotateCounterClockwise45()
	  {
		throw new System.NotSupportedException("This luminance source does not support rotation by 45 degrees.");
	  }

	  public override string ToString()
	  {
		sbyte[] row = new sbyte[width];
		StringBuilder result = new StringBuilder(height * (width + 1));
		for (int y = 0; y < height; y++)
		{
		  row = getRow(y, row);
		  for (int x = 0; x < width; x++)
		  {
			int luminance = row[x] & 0xFF;
			char c;
			if (luminance < 0x40)
			{
			  c = '#';
			}
			else if (luminance < 0x80)
			{
			  c = '+';
			}
			else if (luminance < 0xC0)
			{
			  c = '.';
			}
			else
			{
			  c = ' ';
			}
			result.Append(c);
		  }
		  result.Append('\n');
		}
		return result.ToString();
	  }

	}

}