face-api/src/dom/getContext2dOrThrow.ts

24 lines
673 B
TypeScript

import { env } from '../env/index';
import { resolveInput } from './resolveInput';
export function getContext2dOrThrow(canvasArg: string | HTMLCanvasElement | CanvasRenderingContext2D): CanvasRenderingContext2D {
const { Canvas, CanvasRenderingContext2D } = env.getEnv();
if (canvasArg instanceof CanvasRenderingContext2D) {
return canvasArg;
}
const canvas = resolveInput(canvasArg);
if (!(canvas instanceof Canvas)) {
throw new Error('resolveContext2d - expected canvas to be of instance of Canvas');
}
const ctx = canvas.getContext('2d');
if (!ctx) {
throw new Error('resolveContext2d - canvas 2d context is null');
}
return ctx;
}