uppy/packages/@uppy/utils/src/canvasToBlob.js

const dataURItoBlob = require('./dataURItoBlob')

/**
 * Save a <canvas> element's content to a Blob object.
 *
 * @param {HTMLCanvasElement} canvas
 * @return {Promise}
 */
module.exports = function canvasToBlob (canvas, type, quality) {
  if (canvas.toBlob) {
    return new Promise((resolve) => {
      canvas.toBlob(resolve, type, quality)
    })
  }
  return Promise.resolve().then(() => {
    return dataURItoBlob(canvas.toDataURL(type, quality), {})
  })
}