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 CodeLibrary
{
   public  class ImageHelper
    {  /// <summary>
       /// 图像灰度化
       /// </summary>
       /// <param name="bmp"></param>
       /// <returns></returns>
        public static Bitmap ToGray(Bitmap bmp)
        {
            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    //获取该点的像素的RGB的颜色
                    Color color = bmp.GetPixel(i, j);
                    //利用公式计算灰度值
                    int gray = (int)(color.R * 0.3 + color.G * 0.59 + color.B * 0.11);
                    Color newColor = Color.FromArgb(gray, gray, gray);
                    bmp.SetPixel(i, j, newColor);
                }
            }
            return bmp;
        }
        /// <summary>
        /// 图像灰度反转
        /// </summary>
        /// <param name="bmp"></param>
        /// <returns></returns>
        public static Bitmap GrayReverse(Bitmap bmp)
        {
            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    //获取该点的像素的RGB的颜色
                    Color color = bmp.GetPixel(i, j);
                    Color newColor = Color.FromArgb(255 - color.R, 255 - color.G, 255 - color.B);
                    bmp.SetPixel(i, j, newColor);
                }
            }
            return bmp;
        }
        /// <summary>
         /// 图像二值化1：取图片的平均灰度作为阈值，低于该值的全都为0，高于该值的全都为255
         /// </summary>
         /// <param name="bmp"></param>
         /// <returns></returns>
        public static Bitmap ConvertTo1Bpp1(Bitmap bmp)
        {
            int average = 0;
            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    Color color = bmp.GetPixel(i, j);
                    average += color.B;
                }
            }
            average = (int)average / (bmp.Width * bmp.Height);

            for (int i = 0; i < bmp.Width; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                    //获取该点的像素的RGB的颜色
                    Color color = bmp.GetPixel(i, j);
                    int value = 255 - color.B;
                    Color newColor = value > average ? Color.FromArgb(0, 0, 0) : Color.FromArgb(255, 255, 255);
                    bmp.SetPixel(i, j, newColor);
                }
            }
            return bmp;
        }

        /// <summary>
        /// 图像二值化2
        /// </summary>
        /// <param name="img"></param>
        /// <returns></returns>
        public static Bitmap ConvertTo1Bpp2(Bitmap img)
        {
            int w = img.Width;
            int h = img.Height;
            Bitmap bmp = new Bitmap(w, h, PixelFormat.Format1bppIndexed);
            BitmapData data = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);
            for (int y = 0; y < h; y++)
            {
                byte[] scan = new byte[(w + 7) / 8];
                for (int x = 0; x < w; x++)
                {
                    Color c = img.GetPixel(x, y);
                    if (c.GetBrightness() >= 0.5) scan[x / 8] |= (byte)(0x80 >> (x % 8));
                }
                Marshal.Copy(scan, 0, (IntPtr)((int)data.Scan0 + data.Stride * y), scan.Length);
            }
            return bmp;
        }
        /// <summary>
         /// 图像明暗调整
         /// </summary>
         /// <param name="b">原始图</param>
         /// <param name="degree">亮度[-255, 255]</param>
         /// <returns></returns>
        public static Bitmap KiLighten(Bitmap b, int degree)
        {
            if (b == null)
            {
                return null;
            }

            if (degree < -255) degree = -255;
            if (degree > 255) degree = 255;

            try
            {

                int width = b.Width;
                int height = b.Height;

                int pix = 0;

                BitmapData data = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

                unsafe
                {
                    byte* p = (byte*)data.Scan0;
                    int offset = data.Stride - width * 3;
                    for (int y = 0; y < height; y++)
                    {
                        for (int x = 0; x < width; x++)
                        {
                            // 处理指定位置像素的亮度
                            for (int i = 0; i < 3; i++)
                            {
                                pix = p[i] + degree;

                                if (degree < 0) p[i] = (byte)Math.Max(0, pix);
                                if (degree > 0) p[i] = (byte)Math.Min(255, pix);

                            } // i
                            p += 3;
                        } // x
                        p += offset;
                    } // y
                }

                b.UnlockBits(data);

                return b;
            }
            catch
            {
                return null;
            }

        } // end of Lighten
    }
}