Method GetWaveform

src/Frame.cpp:159–248

Get an audio waveform image

// Get an audio waveform image
std::shared_ptr<QImage> Frame::GetWaveform(int width, int height, int Red, int Green, int Blue, int Alpha)
{
	// Clear any existing waveform image
	ClearWaveform();

	// Init a list of lines
	QVector<QPointF> lines;
	QVector<QPointF> labels;

	// Calculate width of an image based on the # of samples
	int total_samples = GetAudioSamplesCount();
	if (total_samples > 0)
	{
		// If samples are present...
		int new_height = 200 * audio->getNumChannels();
		int height_padding = 20 * (audio->getNumChannels() - 1);
		int total_height = new_height + height_padding;
		int total_width = 0;
		float zero_height = 1.0; // Used to clamp near-zero vales to this value to prevent gaps

		// Loop through each audio channel
		float Y = 100.0;
		for (int channel = 0; channel < audio->getNumChannels(); channel++)
		{
			float X = 0.0;

			// Get audio for this channel
			const float *samples = audio->getReadPointer(channel);

			for (int sample = 0; sample < GetAudioSamplesCount(); sample++, X++)
			{
				// Sample value (scaled to -100 to 100)
				float value = samples[sample] * 100.0;

				// Set threshold near zero (so we don't allow near-zero values)
				// This prevents empty gaps from appearing in the waveform
				if (value > -zero_height && value < 0.0) {
					value = -zero_height;
				} else if (value > 0.0 && value < zero_height) {
					value = zero_height;
				}

				// Append a line segment for each sample
				lines.push_back(QPointF(X, Y));
				lines.push_back(QPointF(X, Y - value));
			}

			// Add Channel Label Coordinate
			labels.push_back(QPointF(5.0, Y - 5.0));

			// Increment Y
			Y += (200 + height_padding);
			total_width = X;
		}

		// Create blank image
		wave_image = std::make_shared<QImage>(
			total_width, total_height, QImage::Format_RGBA8888_Premultiplied);