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

{

/// <summary>

/// This class converts a collection of FFTs to a colormapped spectrogram image

/// </summary>

public class ImageMaker

{

/// <summary>

/// Colormap used to translate intensity to pixel color

/// </summary>

public Colormap Colormap;

/// <summary>

/// Intensity is multiplied by this number before converting it to the pixel color according to the colormap

/// </summary>

public double Intensity = 1;

/// <summary>

/// If True, intensity will be log-scaled to represent Decibels

/// </summary>

public bool IsDecibel = false;

/// <summary>

/// If <see cref="IsDecibel"/> is enabled, intensity will be scaled by this value prior to log transformation

/// </summary>

public double DecibelScaleFactor = 1;

/// <summary>

/// If False, the spectrogram will proceed in time from left to right across the whole image.

/// If True, the image will be broken and the newest FFTs will appear on the left and oldest on the right.

/// </summary>

public bool IsRoll = false;

/// <summary>

/// If <see cref="IsRoll"/> is enabled, this value indicates the pixel position of the break point.

/// </summary>

public int RollOffset = 0;

/// <summary>

/// If True, the spectrogram will flow top-down (oldest to newest) rather than left-right.

/// </summary>

public bool IsRotated = false;

public ImageMaker()

{

}

public Bitmap GetBitmap(List<double[]> ffts)

{

if (ffts.Count == 0)

throw new ArgumentException("Not enough data in FFTs to generate an image yet.");

int Width = IsRotated ? ffts[0].Length : ffts.Count;

int Height = IsRotated ? ffts.Count : ffts[0].Length;

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

Colormap.Apply(bmp);

Rectangle lockRect = new(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 (IsRoll)

{

sourceCol += Width - RollOffset % Width;

if (sourceCol >= Width)

sourceCol -= Width;

}

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

{

double value = IsRotated

? ffts[Height - row - 1][sourceCol]

: ffts[sourceCol][row];

if (IsDecibel)

value = 20 * Math.Log10(value * DecibelScaleFactor + 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;

}

}

}