auto-rotate/index.js

Auto rotate JPEG images based on their EXIF Orientation tag. Promise based API.

"use strict";
var fs = require("fs"),
  jimp = require("jimp"),
  exifParser = require("exif-parser"),
  fs = require("fs-extra"),
  Promise = require("bluebird");

exports.exifFromFile = function(path) {
  return new Promise(function(resolve, reject) {
    fs.open(path, "r", function(err, fd) {
      if (err) return reject(err);

      // Read first 64K of image file (EXIF data located here)
      var headSize = 65536;
      var buffer = new Buffer(headSize);
      fs.read(fd, buffer, 0, buffer.length, null, function(
        err,
        bytesRead,
        buffer
      ) {
        fs.close(fd);
        if (err) return reject(err);
        try {
          var parser = exifParser.create(buffer);
          var result = parser.parse();
          resolve(result);
        } catch (exifError) {
          reject(exifError);
        }
      });
    });
  });
};

exports.autoRotateFile = function(source, destination) {
  return this.exifFromFile(source).then(function(exif) {
    return new Promise(function(resolve, reject) {
      jimp.read(source, function(err, image) {
        if (err) return reject(err);

        var rotatedImage = rotate(exif.tags.Orientation, image);
        if (rotatedImage) {
          rotatedImage.write(destination, function(err) {
            if (err) return reject(err);
            resolve(rotatedImage);
          });
        } else if (source !== destination) {
          fs.copy(source, destination, function(err) {
            if (err) return reject(err);
            resolve();
          });
        } else {
          resolve();
        }
      });
    });
  });
};

function rotate(currentOrientation, image) {
  switch (currentOrientation) {
    case 1:
      return; // top-left  - no transform
    case 2:
      return image.flip("horz"); //	top-right - flip horizontal
    case 3:
      return image.rotate(180); // bottom-right - rotate 180
    case 4:
      return image.flip("vert"); // bottom-left - flip vertically
    case 5:
      return image.rotate(90).flip("horz"); // left-top - rotate 90 and flip horizontal
    case 6:
      return image.rotate(90); //	right-top - rotate 90
    case 7:
      return image.rotate(270).flip("horz"); // right-bottom - rotate 270 and flip horizontal
    case 8:
      return image.rotate(270); // left-bottom - rotate 270
  }
}