using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;

namespace WindowsFormsApp5
{
    public static class ImageFilter
    {
        public static Image FilterImage(this Image inputImage, FilterStyle style)
        {
            Bitmap outputImage = new Bitmap(inputImage.Width, inputImage.Height);
            Graphics G = Graphics.FromImage(outputImage);
            G.DrawImage(inputImage, 0, 0);

            if (style == FilterStyle.SemiTransparentColor) { G.FillRectangle(new SolidBrush(Color.FromArgb(50, Color.Red)), 0, 0, outputImage.Width, outputImage.Height); }
            if (style == FilterStyle.Vignette)
            {
                Brush b;
                b = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, outputImage.Width / 2, outputImage.Height), Color.Black, Color.Transparent, 360);
                G.FillRectangle(b, 0, 0, outputImage.Width / 2, outputImage.Height);
                b = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, outputImage.Width / 2, outputImage.Height), Color.Transparent, Color.Black, 360);
                G.FillRectangle(b, outputImage.Width - outputImage.Width / 2, 0, outputImage.Width / 2, outputImage.Height);
                b = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, outputImage.Width, outputImage.Height / 2), Color.Black, Color.Transparent, 90);
                G.FillRectangle(b, 0, 0, outputImage.Width, outputImage.Height / 2);
                b = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, outputImage.Width, outputImage.Height / 2), Color.Black, Color.Transparent, 270);
                G.FillRectangle(b, 0, outputImage.Height - outputImage.Height / 2 + 1, outputImage.Width, outputImage.Height / 2);
            }
            if (style == FilterStyle.GrayScale)
            {
                for (Int32 y = 0; y < outputImage.Height; y++)
                    for (Int32 x = 0; x < outputImage.Width; x++)
                    {
                        Color c = outputImage.GetPixel(x, y);

                        Int32 gs = (Int32)(c.R * 0.3 + c.G * 0.59 + c.B * 0.11);

                        outputImage.SetPixel(x, y, Color.FromArgb(gs, gs, gs));
                    }
            }
            if (style == FilterStyle.Invert)
            {
                for (int y = 0; (y <= (outputImage.Height - 1)); y++)
                {
                    for (int x = 0; (x <= (outputImage.Width - 1)); x++)
                    {
                        Color inv = outputImage.GetPixel(x, y);
                        inv = Color.FromArgb(255, (255 - inv.R), (255 - inv.G), (255 - inv.B));
                        outputImage.SetPixel(x, y, inv);
                    }
                }
            }
            return outputImage;
        }

        public enum FilterStyle
        {
            SemiTransparentColor, Vignette, GrayScale, Invert
        }
    }
}