html canvas: orient an image to position 1.

ImageHelper.js

/* Usage 
import { readFile, profileOrient, createImage } from '../../helpers/ImageHelper';
readFile(file)
  .then(createImage)
  .then(profileOrient.bind(undefined, file.type))
  .then(blob => {})
*/

// nodemodule used to learn the orientation of an image.
import exif from 'exif-js';

export function readFile(file) {
  return new Promise(resolve => {
    var reader = new FileReader();
    reader.onload = e => resolve(e.target.result);
    reader.readAsDataURL(file);
  });
}

export function createImage(data) {
  return new Promise(resolve => {
    const img = document.createElement('img');
    img.onload = () => resolve(img);
    img.src = data;
  });
}

export function profileOrient(type, img) {
  return new Promise(resolve => {
    const canvas = document.createElement('canvas');

    exif.getData(img, function() {
      var orientation = exif.getAllTags(this).Orientation;

      if ([5, 6, 7, 8].indexOf(orientation) > -1) {
        canvas.width = img.height;
        canvas.height = img.width;
      } else {
        canvas.width = img.width;
        canvas.height = img.height;
      }

      var ctx = canvas.getContext('2d');

      switch (orientation) {
        case 2:
          ctx.transform(-1, 0, 0, 1, img.width, 0);
          break;
        case 3:
          ctx.transform(-1, 0, 0, -1, img.width, img.height);
          break;
        case 4:
          ctx.transform(1, 0, 0, -1, 0, img.height);
          break;
        case 5:
          ctx.transform(0, 1, 1, 0, 0, 0);
          break;
        case 6:
          ctx.transform(0, 1, -1, 0, img.height, 0);
          break;
        case 7:
          ctx.transform(0, -1, -1, 0, img.height, img.width);
          break;
        case 8:
          ctx.transform(0, -1, 1, 0, 0, img.width);
          break;
        default:
          ctx.transform(1, 0, 0, 1, 0, 0);
      }

      ctx.drawImage(img, 0, 0, img.width, img.height);
      ctx.canvas.toBlob(resolve, type);
    });
  });
}