using NUnit.Framework;

using System;

using SkiaSharp;

namespace Spectrogram.Tests

{

class Mel

{

[Test]

public void Test_MelSpectrogram_MelScale()

{

(double[] audio, int sampleRate) = AudioFile.ReadWAV("../../../../../data/cant-do-that-44100.wav");

int fftSize = 4096;

var sg = new SpectrogramGenerator(sampleRate, fftSize, stepSize: 500);

sg.Add(audio);

// Ottieni l'immagine Mel-scaled come SKBitmap

SKBitmap bmpMel = sg.GetBitmapMel(250); // Presuppone che sg abbia un metodo GetSKBitmapMel

using (var image = SKImage.FromBitmap(bmpMel))

using (var data = image.Encode(SKEncodedImageFormat.Png, 100))

{

// Salva l'immagine Mel-scaled

using (var stream = System.IO.File.OpenWrite("../../../../../dev/graphics/halMel-MelScale.png"))

{

data.SaveTo(stream);

}

}

// Ottieni l'immagine originale come SKBitmap

SKBitmap bmpRaw = sg.GetBitmap(); // Presuppone che sg abbia un metodo GetSKBitmap

SKBitmap bmpCropped = new SKBitmap(bmpRaw.Width, bmpMel.Height);

// Disegna bmpRaw su bmpCropped usando SKCanvas

using (var canvas = new SKCanvas(bmpCropped))

{

canvas.Clear(SKColors.Transparent);

canvas.DrawBitmap(bmpRaw, new SKRect(0, bmpMel.Height - bmpRaw.Height, bmpRaw.Width, bmpMel.Height));

}

using (var imageCropped = SKImage.FromBitmap(bmpCropped))

using (var dataCropped = imageCropped.Encode(SKEncodedImageFormat.Png, 100))

{

// Salva l'immagine croppata

using (var streamCropped = System.IO.File.OpenWrite("../../../../../dev/graphics/halMel-LinearCropped.png"))

{

dataCropped.SaveTo(streamCropped);

}

}

}

[Test]

public void Test_Mel_Graph()

{

int specPoints = 4096;

double maxFreq = 50_000;

double maxMel = 2595 * Math.Log10(1 + maxFreq / 700);

Random rand = new Random(1);

double[] freq = ScottPlot.Generate.Consecutive(specPoints, maxFreq / specPoints);

double[] power = ScottPlot.Generate.RandomWalk(specPoints, .02, .5);

var plt1 = new ScottPlot.Plot();

plt1.Add.ScatterLine(freq, power);

int filterSize = 25;

// generate scales

double[] pointsLinear = new double[filterSize + 1];

double[] pointsMel = new double[filterSize + 1];

for (int i = 0; i < filterSize + 1; i++)

{

double thisFreq = maxFreq * i / filterSize;

double thisMel = maxMel * i / filterSize;

pointsLinear[i] = thisFreq;

pointsMel[i] = 700 * (Math.Pow(10, thisMel / 2595d) - 1);

}

// draw rectangles

double[] binStartFreqs = pointsMel;

for (int binIndex = 0; binIndex < binStartFreqs.Length - 2; binIndex++)

{

double freqLow = binStartFreqs[binIndex];

double freqCenter = binStartFreqs[binIndex + 1];

double freqHigh = binStartFreqs[binIndex + 2];

double[] xs = [freqLow, freqCenter, freqHigh];

double[] ys = [0, 1, 0];

var sctr = plt1.Add.ScatterLine(xs, ys);

int indexLow = (int)(specPoints * freqLow / maxFreq);

int indexHigh = (int)(specPoints * freqHigh / maxFreq);

int indexSpan = indexHigh - indexLow;

Console.WriteLine($"bin {binIndex}: [{freqLow} Hz - {freqHigh} Hz] = [{indexLow}:{indexHigh}]");

double binValue = 0;

double binScaleSum = 0;

for (int i = 0; i < indexSpan; i++)

{

double frac = (double)i / indexSpan;

frac = (frac < .5) ? frac * 2 : 1 - frac;

binScaleSum += frac;

binValue += power[indexLow + i] * frac;

}

binValue /= binScaleSum;

plt1.Add.Marker(freqCenter, binValue, ScottPlot.MarkerShape.FilledCircle, 10, sctr.Color);

}

plt1.SavePng("mel1.png", 800, 300);

}

[Test]

public void Test_SaveEmpty_Throws()

{

(double[] audio, int sampleRate) = AudioFile.ReadWAV("../../../../../data/cant-do-that-44100.wav");

int fftSize = 4096;

var spec = new SpectrogramGenerator(sampleRate, fftSize, stepSize: 500);

//spec.Add(audio);

Assert.Throws<InvalidOperationException>(() => { spec.SaveImage("empty.png"); });

}

}

}