//	Spludlow Software
//	Copyright © Samuel P. Ludlow 2020 All Rights Reserved
//	Distributed under the terms of the GNU General Public License version 3
//	Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
//	https://www.spludlow.co.uk/LICENCE.TXT
//	The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
//	v1.14

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

using System.Drawing;

namespace Spludlow.MetSat
{
	public class CLM
	{
		//	2 bit colour source -> Format8bppIndexed PNG

		public static void ProcessGRIB(byte[] gribData, string targetFilename)
		{
			Spludlow.MetSat.GRIB grib = new GRIB(gribData);

			ProcessGRIB(grib, targetFilename);
		}

		public static void ProcessGRIB(Spludlow.MetSat.GRIB grib, string targetFilename)
		{
			System.Drawing.Imaging.PixelFormat pixelFormat = System.Drawing.Imaging.PixelFormat.Format8bppIndexed;

			int width = 3712;
			int height = 3712;

			Color[] pallete = new Color[256];
			for (int index = 0; index < 256; ++index)
				pallete[index] = Color.Yellow;

			pallete[0] = Color.Black;
			pallete[1] = Color.White;
			pallete[2] = Color.Green;
			pallete[3] = Color.Blue;

			using (Bitmap bitmap = new Bitmap(width, height, pixelFormat))
			{
				Spludlow.Drawing.Bitmaps.SetPalette(bitmap, pallete);

				byte[] bitmapData = Spludlow.Drawing.Bitmaps.ReadBitmapData(bitmap, pixelFormat);

				for (int y = 0; y < height; ++y)
				{
					for (int x = 0; x < width; ++x)
					{
						int offset = y * width + x;

						int bitIndex = offset * 2;

						int byteIndex = bitIndex / 8;
						int bitOffset = bitIndex % 8;

						bitOffset /= 2;

						int mask = 3 << ((3 - bitOffset) * 2);

						int value = (int)grib.Data[byteIndex];

						value &= mask;

						value = value >> ((3 - bitOffset) * 2);

						value = 3 - value;

						int targetOffset = (((width - 1) - y) * width) + ((width - 1) - x);	//	? first width should be height ???

						bitmapData[targetOffset] = (byte)value;
					}
				}

				Spludlow.Drawing.Bitmaps.WriteBitmapData(bitmap, bitmapData, pixelFormat);

				bitmap.Save(targetFilename, System.Drawing.Imaging.ImageFormat.Png);
			}
		}
	}
}