/*
* Copyright 2012 ZXing.Net 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;

namespace ZXing
{
    /// <summary>
    /// The base class for luminance sources which supports 
    /// cropping and rotating based upon the luminance values.
    /// </summary>
    public abstract class BaseLuminanceSource : LuminanceSource
    {
        // the following channel weights give nearly the same
        // gray scale picture as the java version with BufferedImage.TYPE_BYTE_GRAY
        // they are used in sub classes for luminance / gray scale calculation
        /// <summary>
        /// weight of the red channel for calculating a gray scale image
        /// </summary>
        protected const int RChannelWeight = 19562;
        /// <summary>
        /// weight of the green channel for calculating a gray scale image
        /// </summary>
        protected const int GChannelWeight = 38550;
        /// <summary>
        /// weight of the blue channel for calculating a gray scale image
        /// </summary>
        protected const int BChannelWeight = 7424;
        /// <summary>
        /// numbers of bits which for right shifting
        /// </summary>
        protected const int ChannelWeight = 16;

        /// <summary>
        /// 
        /// </summary>
        protected byte[] luminances;

        /// <summary>
        /// Initializes a new instance of the <see cref="BaseLuminanceSource"/> class.
        /// </summary>
        /// <param name="width">The width.</param>
        /// <param name="height">The height.</param>
        protected BaseLuminanceSource(int width, int height)
           : base(width, height)
        {
            luminances = new byte[width * height];
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="BaseLuminanceSource"/> class.
        /// </summary>
        /// <param name="luminanceArray">The luminance array.</param>
        /// <param name="width">The width.</param>
        /// <param name="height">The height.</param>
        protected BaseLuminanceSource(byte[] luminanceArray, int width, int height)
           : base(width, height)
        {
            luminances = new byte[width * height];
            Buffer.BlockCopy(luminanceArray, 0, luminances, 0, width * height);
        }

        /// <summary>
        /// Fetches one row of luminance data from the underlying platform's bitmap. Values range from
        /// 0 (black) to 255 (white). 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 &lt;= y &lt; Height.</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>
        override public byte[] getRow(int y, byte[] row)
        {
            int width = Width;
            if (row == null || row.Length < width)
            {
                row = new byte[width];
            }
            for (int i = 0; i < width; i++)
                row[i] = luminances[y * width + i];
            return row;
        }

        /// <summary>
        /// gets the luminance matrix
        /// </summary>
        public override byte[] Matrix
        {
            get { return luminances; }
        }

        /// <summary>
        /// Returns a new object with rotated image data by 90 degrees counterclockwise.
        /// Only callable if {@link #isRotateSupported()} is true.
        /// </summary>
        /// <returns>
        /// A rotated version of this object.
        /// </returns>
        public override LuminanceSource rotateCounterClockwise()
        {
            var rotatedLuminances = new byte[Width * Height];
            var newWidth = Height;
            var newHeight = Width;
            var localLuminances = Matrix;
            for (var yold = 0; yold < Height; yold++)
            {
                for (var xold = 0; xold < Width; xold++)
                {
                    var ynew = newHeight - xold - 1;
                    var xnew = yold;
                    rotatedLuminances[ynew * newWidth + xnew] = localLuminances[yold * Width + xold];
                }
            }
            return CreateLuminanceSource(rotatedLuminances, newWidth, newHeight);
        }

        /// <summary>
        /// TODO: not implemented yet
        /// </summary>
        /// <returns>
        /// A rotated version of this object.
        /// </returns>
        public override LuminanceSource rotateCounterClockwise45()
        {
            // TODO: implement a good 45 degrees rotation without lost of information
            return base.rotateCounterClockwise45();
        }

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

        /// <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 CropSupported is true.
        /// </summary>
        /// <param name="left">The left coordinate, 0 &lt;= left &lt; Width.</param>
        /// <param name="top">The top coordinate, 0 &lt;= top &lt;= Height.</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 override LuminanceSource crop(int left, int top, int width, int height)
        {
            if (left + width > Width || top + height > Height)
            {
                throw new ArgumentException("Crop rectangle does not fit within image data.");
            }
            var croppedLuminances = new byte[width * height];
            var oldLuminances = Matrix;
            var oldWidth = Width;
            var oldRightBound = left + width;
            var oldBottomBound = top + height;
            for (int yold = top, ynew = 0; yold < oldBottomBound; yold++, ynew++)
            {
                for (int xold = left, xnew = 0; xold < oldRightBound; xold++, xnew++)
                {
                    croppedLuminances[ynew * width + xnew] = oldLuminances[yold * oldWidth + xold];
                }
            }
            return CreateLuminanceSource(croppedLuminances, width, height);
        }

        /// <summary>
        /// </summary>
        /// <returns> Whether this subclass supports cropping.</returns>
        public override bool CropSupported
        {
            get
            {
                return true;
            }
        }

        /// <summary>
        /// </summary>
        /// <returns>Whether this subclass supports invertion.</returns>
        public override bool InversionSupported
        {
            get
            {
                return true;
            }
        }

        /// <summary>
        /// Inverts the luminance values (newValue = 255 - oldValue)
        /// </summary>
        public override LuminanceSource invert()
        {
            return new InvertedLuminanceSource(this);
        }

        /// <summary>
        /// Should create a new luminance source with the right class type.
        /// The method is used in methods crop and rotate.
        /// </summary>
        /// <param name="newLuminances">The new luminances.</param>
        /// <param name="width">The width.</param>
        /// <param name="height">The height.</param>
        /// <returns></returns>
        protected abstract LuminanceSource CreateLuminanceSource(byte[] newLuminances, int width, int height);
    }
}