using System;

using System.Collections.Generic;

using System.Drawing;

using System.Drawing.Imaging;

using System.Runtime.InteropServices;

using System.Text;

using System.Threading.Tasks;

namespace Spectrogram

{

public static class Image

{

public static Bitmap GetBitmap(List<double[]> ffts, Colormap cmap, double intensity = 1, bool dB = false, bool roll = false, int rollOffset = 0)

{

if (ffts.Count == 0)

throw new ArgumentException("This Spectrogram contains no FFTs (likely because no signal was added)");

int Width = ffts.Count;

int Height = ffts[0].Length;

Bitmap bmp = new Bitmap(Width, Height, PixelFormat.Format8bppIndexed);

cmap.Apply(bmp);

var lockRect = new Rectangle(0, 0, Width, Height);

BitmapData bitmapData = bmp.LockBits(lockRect, ImageLockMode.ReadOnly, bmp.PixelFormat);

int stride = bitmapData.Stride;

byte[] bytes = new byte[bitmapData.Stride * bmp.Height];

Parallel.For(0, Width, col =>

{

int sourceCol = col;

if (roll)

{

sourceCol += Width - rollOffset % Width;

if (sourceCol >= Width)

sourceCol -= Width;

}

for (int row = 0; row < Height; row++)

{

double value = ffts[sourceCol][row];

if (dB)

value = 20 * Math.Log10(value + 1);

value *= intensity;

value = Math.Min(value, 255);

int bytePosition = (Height - 1 - row) * stride + col;

bytes[bytePosition] = (byte)value;

}

});

Marshal.Copy(bytes, 0, bitmapData.Scan0, bytes.Length);

bmp.UnlockBits(bitmapData);

return bmp;

}

}

}