/** helper functions for generating spectrograms */
import { AudioInformation } from "./audioInformation";
import { SpectrogramOptions } from "../../components/spectrogram/spectrogramOptions";
/**
 * A class to generate a spectrogram from an sample buffer.
 * The output is a Uint8ClampedArray that can be painted into a canvas.
 * This is a big messy, stateful, side-effecty class that is designed to
 * reduce allocations and improve performance.
 */
export declare class SpectrogramGenerator {
    #private;
    private audio;
    private options;
    private fft;
    private fftWidth;
    private fftHeight;
    private smooth;
    private colorScale;
    private melScale;
    /** This is the last column of spectrum we converted into pixels */
    private lastFrameIndex;
    private imageBuffer;
    private readonly fftOutput;
    private readonly complexInput;
    private readonly window;
    private readonly spectrum;
    readonly estimatedWindowLoss: number;
    private readonly amplificationFactor;
    constructor(audio: AudioInformation, options: SpectrogramOptions);
    get nyquist(): number;
    get step(): number;
    get size(): number;
    get outputBuffer(): Uint8ClampedArray;
    get width(): number;
    get height(): number;
    get totalSamples(): number;
    /**
     * Generate a 2D spectrogram from the audio samples.
     * Assumes a progressive rendering scenario where the audio samples are
     * continuously fed into the spectrogram.
     * If it can't fill a window with samples, it will wait partially consume the current buffer with the assumption
     * the next buffer will include the unconsumed samples.
     * To indicate the end of the audio stream supply `consumeAll = true` to consume all samples in the buffer.
     * @param samples The audio samples to generate the spectrogram from.
     * @param lastSampleIndex The index of the last sample in the input buffer.
     *  The buffer may have more samples than this but they should be considered uninitialized memory.
     * @param consumeAll If true, the function will consume all samples in the buffer.
     * @returns The number of samples consumed from the input buffer.
     */
    partialGenerate(samples: Float32Array, lastSampleIndex: number, consumeAll: boolean): number;
    private extractWindow;
    private interleaveReals;
    /**
     * Converts the output of the fft into a magnitude and scales it.
     * We keep only the positive frequencies and discard the dc offset and negative frequencies.
     * @param fftOutput The output of the fft.
     * @param spectrum The array to store the magnitude of the fft.
     * @param windowSize
     */
    private extractMagnitudeAndScale;
    private paintSpectrumIntoPixelBuffer;
}