/// <summary>
/// Get a spectrogram of the signal specified at the input
/// </summary>
/// <param name="spectrogram">Signal</param>
/// <param name="width">Width of the image</param>
/// <param name="height">Height of the image</param>
/// <param name="milliseconds">Time in ms</param>
/// <param name="sampleRate">Sample rate in hz</param>
/// <param name="colorPalette">Specify to color palette</param>
/// <param name="doLogScale">log scale or not?</param>
/// <param name="logFrequenciesIndex">log frequency index array</param>
/// <param name="logFrequencies">log frequency array</param>
/// <remarks>
/// X axis - time
/// Y axis - frequency
/// Color - magnitude level of corresponding band value of the signal
/// <returns>Spectral image of the signal</returns>
public static Bitmap GetSpectrogramImage(float[][] spectrogram, int width, int height, double milliseconds, double sampleRate, ColorUtils.ColorPaletteType colorPalette, bool doLogScale, int[] logFrequenciesIndex, float[] logFrequencies)
{
#if SAFE
if (width < 0)
throw new ArgumentException("width should be bigger than 0");
if (height < 0)
throw new ArgumentException("height should be bigger than 0");
#endif
bool drawLabels = true;
float minDb = -90.0f; // -80.0f also works good
float maxDb = 10.0f; // with the current color palettes 10.0f works well
// Basic constants
int TOTAL_HEIGHT = height; // Height of graph
int TOTAL_WIDTH = width; // Width of graph
int TOP = 40; // Top of graph
int LEFT = 60; // Left edge of graph
int HEIGHT = height-2*TOP; // Height of graph
int WIDTH = width-2*LEFT; // Width of graph
string LABEL_X = "Time (ms)"; // Label for X axis
string LABEL_Y = "Frequency (Hz)"; // Label for Y axis
float MAX_FREQ = (float) sampleRate / 2; // Maximum frequency (Hz) on vertical axis.
float MIN_FREQ = 27.5f; // Minimum frequency (Hz) on vertical axis.
float FREQ_STEP = 1000; // Interval between ticks (dB) on vertical axis.
// if the max frequency gets lower than ... lower the frequency step
if (MAX_FREQ < 20000) {
FREQ_STEP = (float) MathUtils.GetNicerNumber(MAX_FREQ / 20);
}
// Derived constants
int BOTTOM = TOTAL_HEIGHT-TOP; // Bottom of graph
float FREQTOPIXEL = (float) HEIGHT/(MAX_FREQ-MIN_FREQ); // Pixels/Hz
float MIN_TIME = 0.0f;
float MAX_TIME = (float) milliseconds;
if (MAX_TIME == 0) MAX_TIME = 1000;
// Interval between ticks (time) on horizontal axis.
float TIME_STEP = (float) MathUtils.GetNicerNumber(MAX_TIME / 20);
float TIMETOPIXEL = (float) WIDTH/(MAX_TIME-MIN_TIME); // Pixels/second
// Colors
// black, gray, white style
Color lineColor = ColorTranslator.FromHtml("#BFBFBF");
Color middleLineColor = ColorTranslator.FromHtml("#BFBFBF");
Color labelColor = ColorTranslator.FromHtml("#FFFFFF");
Color tickColor = ColorTranslator.FromHtml("#BFBFBF");
Color fillOuterColor = ColorTranslator.FromHtml("#000000");
Color fillColor = ColorTranslator.FromHtml("#000000");
Bitmap fullImage = new Bitmap(TOTAL_WIDTH, TOTAL_HEIGHT);
Graphics g = Graphics.FromImage(fullImage);
Pen linePen = new Pen(lineColor, 0.5f);
Pen middleLinePen = new Pen(middleLineColor, 0.5f);
Pen labelPen = new Pen(labelColor, 1);
Pen tickPen = new Pen(tickColor, 1);
// Draw a rectangular box marking the boundaries of the graph
Rectangle rectOuter = new Rectangle(0, 0, TOTAL_WIDTH, TOTAL_HEIGHT);
Brush fillBrushOuter = new SolidBrush(fillOuterColor);
g.FillRectangle(fillBrushOuter, rectOuter);
// Create rectangle.
Rectangle rect = new Rectangle(LEFT, TOP, WIDTH, HEIGHT);
Brush fillBrush = new SolidBrush(fillColor);
g.FillRectangle(fillBrush, rect);
g.DrawRectangle(linePen, rect);
// Label for horizontal axis
Font drawLabelFont = new Font("Arial", 8);
SolidBrush drawLabelBrush = new SolidBrush(labelPen.Color);
if (drawLabels) {
SizeF drawLabelTextSize = g.MeasureString(LABEL_X, drawLabelFont);
g.DrawString(LABEL_X, drawLabelFont, drawLabelBrush, (TOTAL_WIDTH/2) - (drawLabelTextSize.Width/2), TOTAL_HEIGHT - drawLabelFont.GetHeight(g) - 5);
}
float y = 0;
float yMiddle = 0;
float x = 0;
float xMiddle = 0;
if (!doLogScale) {
// LINEAR SCALE
// Tick marks on the vertical axis
for ( float freqTick = MIN_FREQ; freqTick <= MAX_FREQ; freqTick += FREQ_STEP )
{
// draw horozontal main line
y = BOTTOM - FREQTOPIXEL*(freqTick-MIN_FREQ);
if (y < BOTTOM && y > TOP+1) {
g.DrawLine(linePen, LEFT-2, y, LEFT+WIDTH+2, y);
}
// draw horozontal middle line (between the main lines)
yMiddle = y-(FREQTOPIXEL*FREQ_STEP)/2;
if (yMiddle > TOP && yMiddle < HEIGHT+TOP) {
g.DrawLine(middleLinePen, LEFT, yMiddle, LEFT+WIDTH, yMiddle);
}
if ( freqTick != MAX_FREQ )
{
// Numbers on the tick marks
Font drawFont = new Font("Arial", 8);
SolidBrush drawBrush = new SolidBrush(tickPen.Color);
// left
g.DrawString(MathUtils.FormatNumber((int) freqTick), drawFont, drawBrush, LEFT - 33, y - drawFont.GetHeight(g)/2);
// right
g.DrawString(MathUtils.FormatNumber((int) freqTick), drawFont, drawBrush, WIDTH + LEFT + 4, y - drawFont.GetHeight(g)/2);
}
}
} else {
// LOG SCALE
for (int i = 0; i < logFrequencies.Length; i+=20)
{
float freqTick = logFrequencies[i];
y = BOTTOM - i;
// draw horozontal main line
if (y < BOTTOM && y > TOP+1) {
g.DrawLine(linePen, LEFT-2, y, LEFT+WIDTH+2, y);
}
// Numbers on the tick marks
Font drawFont = new Font("Arial", 8);
SolidBrush drawBrush = new SolidBrush(tickPen.Color);
// left
g.DrawString(MathUtils.FormatNumber((int) freqTick), drawFont, drawBrush, LEFT - 33, y - drawFont.GetHeight(g)/2);
// right
g.DrawString(MathUtils.FormatNumber((int) freqTick), drawFont, drawBrush, WIDTH + LEFT + 4, y - drawFont.GetHeight(g)/2);
}
}
if (drawLabels) {
// Label for vertical axis
StringFormat format = new StringFormat();
format.Alignment = StringAlignment.Center;
g.TranslateTransform(g.VisibleClipBounds.Width, 0);
g.RotateTransform(270);
g.DrawString(LABEL_Y, drawLabelFont, drawLabelBrush, -(TOTAL_HEIGHT/2), -TOTAL_WIDTH + 5, format);
g.ResetTransform();
}
// Tick marks on the horizontal axis
for ( float timeTick = MIN_TIME; timeTick <= MAX_TIME; timeTick += TIME_STEP )
{
// draw vertical main line
x = LEFT + TIMETOPIXEL*(timeTick-MIN_TIME);
if (x > LEFT && x < WIDTH) {
g.DrawLine(linePen, x, BOTTOM+2, x, TOP-2);
}
// draw vertical middle line (between the main lines)
xMiddle = x + TIMETOPIXEL*TIME_STEP/2;
if (xMiddle < WIDTH+LEFT) {
g.DrawLine(middleLinePen, xMiddle, BOTTOM, xMiddle, TOP);
}
if ( timeTick != MIN_TIME && timeTick != MAX_TIME )
{
// Numbers on the tick marks
Font drawFont = new Font("Arial", 8);
SolidBrush drawBrush = new SolidBrush(tickPen.Color);
SizeF drawTimeTickTextSize = g.MeasureString("" + timeTick, drawFont);
// top
g.DrawString("" + timeTick, drawFont, drawBrush, x-(drawTimeTickTextSize.Width/2), TOP - 15);
// bottom
g.DrawString("" + timeTick, drawFont, drawBrush, x-(drawTimeTickTextSize.Width/2), BOTTOM + 2);
}
}
// draw spectrogram
Bitmap spectrogramImage = new Bitmap(WIDTH, HEIGHT);
// calculate min and max
double max = spectrogram.Max((b) => b.Max((v) => Math.Abs(v)));
double min = spectrogram.Min((b) => b.Min((v) => Math.Abs(v)));
int numberOfSamplesX = spectrogram.Length; // time
int numberOfSamplesY = spectrogram[0].Length; // hz
double deltaX = (double) (WIDTH - 1)/(numberOfSamplesX); // By how much the image will move to the left
double deltaY = (double) (HEIGHT- 1)/(numberOfSamplesY); // By how much the image will move upward
int prevX = 0;
Color prevColor = Color.Black;
for (int i = 0; i < numberOfSamplesX; i++)
{
double xCoord = i*deltaX;
if ((int) xCoord == prevX) continue;
for (int j = 0; j < numberOfSamplesY; j++)
{
float amplitude = spectrogram[i][j];
Color colorbw = Color.Black;
if (amplitude > 0) {
float dB = MathUtils.AmplitudeToDecibel(amplitude, minDb, maxDb);
int colorval = (int) MathUtils.ConvertAndMainainRatio(dB, minDb, maxDb, 0, 255); // 255 is full brightness, and good for REW colors (for SOX 220 is good, and for PHOTOSOUNDER 245 seems good)
colorbw = Color.FromArgb(colorval, colorval, colorval);
//colorbw = ValueToBlackWhiteColor(amplitude, max*0.010);
prevColor = colorbw;
} else {
colorbw = prevColor;
}
spectrogramImage.SetPixel((int) xCoord + 1, HEIGHT - (int) (deltaY*j) - 1, colorbw);
}
prevX = (int) xCoord;
}
if (colorPalette != ColorUtils.ColorPaletteType.BLACK_AND_WHITE) {
spectrogramImage = ColorUtils.Colorize(spectrogramImage, 255, colorPalette);
}
// add the spectrogram to the full image
g.DrawImage(spectrogramImage, LEFT, TOP);
return fullImage;
}
/// <summary>
/// Utility method to return spectrogram image using audio data
/// </summary>
/// <param name="audioData"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <param name="sampleRate"></param>
/// <param name="fftWindowsSize"></param>
/// <param name="fftOverlap"></param>
/// <param name="colorPalette"></param>
/// <param name="doLogScale"></param>
/// <returns>Spectrogram image</returns>
public static Bitmap GetSpectrogramImage(float[] audioData, int width, int height, double sampleRate, int fftWindowsSize, int fftOverlap, ColorUtils.ColorPaletteType colorPalette, bool doLogScale)
{
float[][] spectrogram;
double minFrequency = 27.5;
double maxFrequency = sampleRate / 2;
int logBins = height - 2*40; // the margins used
int[] logFrequenciesIndex = new int[1];
float[] logFrequencies = new float[1];
// find the time
int numberOfSamples = audioData.Length;
double seconds = numberOfSamples / sampleRate;
if (!doLogScale) {
spectrogram = CreateSpectrogramLomont(audioData, fftWindowsSize, fftOverlap);
} else {
// calculate the log frequency index table
GetLogFrequenciesIndex(sampleRate, minFrequency, maxFrequency, logBins, fftWindowsSize, LogBase, out logFrequenciesIndex, out logFrequencies);
spectrogram = CreateLogSpectrogramLomont(audioData, fftWindowsSize, fftOverlap, logBins, logFrequenciesIndex, logFrequencies);
}
return GetSpectrogramImage(spectrogram, width, height, seconds*1000, sampleRate, colorPalette, doLogScale, logFrequenciesIndex, logFrequencies);
}
