/*
* 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;
using Windows.UI;
using Windows.UI.Xaml.Media.Imaging;

namespace ZXing
{
    /// <summary>
    /// class which represents the luminance values for a bitmap object of a WriteableBitmap class
    /// </summary>
    public partial class BitmapLuminanceSource : BaseLuminanceSource
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="BitmapLuminanceSource"/> class.
        /// </summary>
        /// <param name="width">The width.</param>
        /// <param name="height">The height.</param>
        protected BitmapLuminanceSource(int width, int height)
           : base(width, height)
        {
        }

        /// <summary>
        /// initializing constructor
        /// </summary>
        /// <param name="writeableBitmap"></param>
        [System.CLSCompliant(false)]
        public BitmapLuminanceSource(WriteableBitmap writeableBitmap)
           : base(writeableBitmap.PixelWidth, writeableBitmap.PixelHeight)
        {
            var height = writeableBitmap.PixelHeight;
            var width = writeableBitmap.PixelWidth;

            // In order to measure pure decoding speed, we convert the entire image to a greyscale array
            // luminance array is initialized with new byte[width * height]; in base class

            var data = System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions.ToArray(writeableBitmap.PixelBuffer, 0, (int)writeableBitmap.PixelBuffer.Length);
            if (data.Length != writeableBitmap.PixelBuffer.Length)
            {
                throw new InvalidOperationException(String.Format("The WriteableBitmap instance isn't correct initialized. The PixelBuffer length is {0}, but the resulting data array is {1}", writeableBitmap.PixelBuffer.Length, data.Length));
            }
            var luminanceIndex = 0;
            var maxSourceIndex = width * height * 4;
            if (data.Length != writeableBitmap.PixelBuffer.Length)
            {
                throw new InvalidOperationException(String.Format("The WriteableBitmap instance isn't correct initialized. The PixelBuffer length is {0}, but it should be {1} (height * width * 4)", writeableBitmap.PixelBuffer.Length, maxSourceIndex));
            }
            for (var sourceIndex = 0; sourceIndex < maxSourceIndex; sourceIndex += 4)
            {
                var c = Color.FromArgb(
                   data[sourceIndex],
                   data[sourceIndex + 1],
                   data[sourceIndex + 2],
                   data[sourceIndex + 3]);
                luminances[luminanceIndex] = (byte)((RChannelWeight * c.R + GChannelWeight * c.G + BChannelWeight * c.B) >> ChannelWeight);
                luminanceIndex++;
            }
        }

        /// <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 override LuminanceSource CreateLuminanceSource(byte[] newLuminances, int width, int height)
        {
            return new BitmapLuminanceSource(width, height) { luminances = newLuminances };
        }
    }
}