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https://github.com/Boof2015/astra-mobile.git
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Boof2015
84 lines
2.7 KiB
TypeScript
84 lines
2.7 KiB
TypeScript
// Coordinate mapping + response-curve sampling for the EQ graph. Frequency is on a
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// log axis (20 Hz–20 kHz); gain is linear (±12 dB) centered vertically.
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import { Skia, type SkPath } from '@shopify/react-native-skia';
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import type { EQBand } from '@/types/audio';
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import {
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EQ_MAX_FREQUENCY,
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EQ_MAX_GAIN_DB,
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EQ_MIN_FREQUENCY,
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computeCombinedEQMagnitude,
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} from '@/audio/eq';
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export const GRAPH_SAMPLE_RATE = 48000;
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export const GRAPH_PAD_Y = 14; // px headroom so ±12 dB nodes aren't clipped
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const LOG_MIN = Math.log10(EQ_MIN_FREQUENCY);
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const LOG_MAX = Math.log10(EQ_MAX_FREQUENCY);
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const LOG_SPAN = LOG_MAX - LOG_MIN;
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function clamp(v: number, min: number, max: number): number {
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return Math.max(min, Math.min(max, v));
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}
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export function freqToX(freq: number, width: number): number {
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const f = clamp(freq, EQ_MIN_FREQUENCY, EQ_MAX_FREQUENCY);
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return ((Math.log10(f) - LOG_MIN) / LOG_SPAN) * width;
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}
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export function xToFreq(x: number, width: number): number {
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const t = clamp(width > 0 ? x / width : 0, 0, 1);
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return 10 ** (LOG_MIN + t * LOG_SPAN);
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}
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export function gainToY(gainDb: number, height: number): number {
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const center = height / 2;
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const usable = center - GRAPH_PAD_Y;
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return center - (clamp(gainDb, -EQ_MAX_GAIN_DB, EQ_MAX_GAIN_DB) / EQ_MAX_GAIN_DB) * usable;
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}
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export function yToGain(y: number, height: number): number {
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const center = height / 2;
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const usable = center - GRAPH_PAD_Y;
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if (usable <= 0) return 0;
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return clamp(((center - y) / usable) * EQ_MAX_GAIN_DB, -EQ_MAX_GAIN_DB, EQ_MAX_GAIN_DB);
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}
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/** Combined response curve as a stroked SkPath sampled across the width. */
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export function buildResponsePath(
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bands: readonly EQBand[],
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width: number,
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height: number,
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samples = 96
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): SkPath {
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const path = Skia.Path.Make();
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if (width <= 0 || height <= 0) return path;
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for (let i = 0; i <= samples; i++) {
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const x = (i / samples) * width;
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const freq = xToFreq(x, width);
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const db = computeCombinedEQMagnitude(bands, freq, GRAPH_SAMPLE_RATE);
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const y = gainToY(db, height);
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if (i === 0) path.moveTo(x, y);
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else path.lineTo(x, y);
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}
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return path;
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}
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/** Closes a copy of the response path down to the baseline for a soft fill. */
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export function buildResponseFill(line: SkPath, width: number, height: number): SkPath {
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const fill = line.copy();
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fill.lineTo(width, height / 2);
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fill.lineTo(0, height / 2);
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fill.close();
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return fill;
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}
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/** Frequency gridline positions + labels shown along the bottom axis. */
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export const FREQ_TICKS: { freq: number; label: string }[] = [
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{ freq: 30, label: '30' },
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{ freq: 100, label: '100' },
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{ freq: 500, label: '500' },
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{ freq: 1000, label: '1k' },
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{ freq: 5000, label: '5k' },
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{ freq: 15000, label: '15k' },
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];
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