using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace ShadowMerger
{
    public class LockBitmap
    {
        Bitmap source = null;
        IntPtr Iptr = IntPtr.Zero;
        BitmapData bitmapData = null;

        public byte[] Pixels { get; set; }
        public int Depth { get; private set; }
        public int Width { get; private set; }
        public int Height { get; private set; }

        public LockBitmap(Bitmap source)
        {
            this.source = source;
        }

        public void LockBits()
        {
            try
            {
                Width = source.Width;
                Height = source.Height;

                int PixelCount = Width * Height;

                Rectangle rect = new Rectangle(0, 0, Width, Height);

                Depth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);

                if (Depth != 8 && Depth != 24 && Depth != 32)
                {
                    throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");
                }

                bitmapData = source.LockBits(rect, ImageLockMode.ReadWrite,
                                             source.PixelFormat);

                int step = Depth / 8;
                Pixels = new byte[PixelCount * step];
                Iptr = bitmapData.Scan0;

                Marshal.Copy(Iptr, Pixels, 0, Pixels.Length);
            }
            catch
            {
                throw;
            }
        }

        public void UnlockBits()
        {
            try
            {
                Marshal.Copy(Pixels, 0, Iptr, Pixels.Length);

                source.UnlockBits(bitmapData);
            }
            catch
            {
                throw;
            }
        }

        public Color GetPixel(int x, int y)
        {
            Color clr = Color.Empty;

            int
                cCount = Depth / 8,
                i = ((y * Width) + x) * cCount;

            if (i > Pixels.Length - cCount)
                throw new IndexOutOfRangeException();

            if (Depth == 32)
            {
                byte
                    b = Pixels[i],
                    g = Pixels[i + 1],
                    r = Pixels[i + 2],
                    a = Pixels[i + 3];

                clr = Color.FromArgb(a, r, g, b);
            }

            if (Depth == 24)
            {
                byte b = Pixels[i],
                    g = Pixels[i + 1],
                    r = Pixels[i + 2];

                clr = Color.FromArgb(r, g, b);
            }

            if (Depth == 8)
            {
                byte c = Pixels[i];

                clr = Color.FromArgb(c, c, c);
            }

            return clr;
        }

        public void SetPixel(int x, int y, Color color)
        {
            int
                cCount = Depth / 8,
                i = ((y * Width) + x) * cCount;

            if (Depth == 32)
            {
                Pixels[i] = color.B;
                Pixels[i + 1] = color.G;
                Pixels[i + 2] = color.R;
                Pixels[i + 3] = color.A;
            }
            if (Depth == 24)
            {
                Pixels[i] = color.B;
                Pixels[i + 1] = color.G;
                Pixels[i + 2] = color.R;
            }
            if (Depth == 8)
            {
                Pixels[i] = color.B;
            }
        }
    }
}