//Skala szarosci
//(c) 2019 by Tomasz Lubinski
//www.algorytm.org

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;

namespace Szarosc
{
    public partial class Form1 : Form
    {

        /// <summary>
        /// Zainicjuj
        /// </summary>
        public Form1()
        {
            InitializeComponent();
        }

        /// <summary>
        /// Wczytaj obraz
        /// </summary>
        private void wczytaj_Click(object sender, EventArgs e)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.Title = "Otwórz obraz";
            dlg.Filter = "pliki jpg (*.jpg)|*.jpg";
            if (dlg.ShowDialog() == DialogResult.OK)
            {
                picture.Image = new Bitmap(dlg.OpenFile());
                picture.Height = picture.Image.Height;
                picture.Width = picture.Image.Width;
                this.ClientSize = new System.Drawing.Size(Math.Max(picture.Width + 32, 300), picture.Height + 80);
            }
            dlg.Dispose();
        }

        /// <summary>
        /// Efekt negatywu
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void negative_Click(object sender, EventArgs e)
        {
            //Nie rob nic jezeli obraz jest jeszcze niewczytany
            if (picture.Image == null)
            {
                return;
            }

            //Sprawdz format obrazu - sprawdz czy obraz zawiera 3 kanały - RGB
            if (picture.Image.PixelFormat != PixelFormat.Format24bppRgb)
            {
                MessageBox.Show("Nieobsługiwany format pliku!", "Bład", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            //Pobierz wartosc wszystkich punktow obrazu
            Bitmap bitmap = (Bitmap)picture.Image;
            BitmapData bmpData = bitmap.LockBits(new Rectangle(0, 0, picture.Width, picture.Height), ImageLockMode.ReadWrite, bitmap.PixelFormat);
            byte[] pixelValues = new byte[Math.Abs(bmpData.Stride) * picture.Height];
            System.Runtime.InteropServices.Marshal.Copy(bmpData.Scan0, pixelValues, 0, pixelValues.Length);

            //Dla kolejnych punktow obrazu
            for (int i = 0; i < picture.Width*picture.Height; i++)
            {
                //Wartosci kolorow zapisane sa w kolejnosci Blue, Green, Red
                byte value = (byte) (0.299 * pixelValues[3 * i + 2] + 
                                     0.587 * pixelValues[3 * i + 1] + 
                                     0.114 * pixelValues[3 * i]);
                pixelValues[3 * i] = value;
                pixelValues[3 * i + 1] = value;
                pixelValues[3 * i + 2] = value;
            }

            //Wczytaj przetworzony obraz
            System.Runtime.InteropServices.Marshal.Copy(pixelValues, 0, bmpData.Scan0, pixelValues.Length);
            bitmap.UnlockBits(bmpData);
            picture.Refresh();
        }
    }
}