JS Client-Side Exif Orientation: Rotate and Mirror JPEG Images

Question

Digital camera photos are often saved as JPEG with an EXIF \"orientation\" tag. To display correctly, images need to be rotated/mirrored depending on which orientation is se

Answer 1

Mederr's context transform works perfectly. If you need to extract orientation only use this function - you don't need any EXIF-reading libs. Below is a function for re-setting orientation in base64 image. Here's a fiddle for it. I've also prepared a fiddle with orientation extraction demo.

function resetOrientation(srcBase64, srcOrientation, callback) {
  var img = new Image();    

  img.onload = function() {
    var width = img.width,
        height = img.height,
        canvas = document.createElement('canvas'),
        ctx = canvas.getContext("2d");

    // set proper canvas dimensions before transform & export
    if (4 < srcOrientation && srcOrientation < 9) {
      canvas.width = height;
      canvas.height = width;
    } else {
      canvas.width = width;
      canvas.height = height;
    }

    // transform context before drawing image
    switch (srcOrientation) {
      case 2: ctx.transform(-1, 0, 0, 1, width, 0); break;
      case 3: ctx.transform(-1, 0, 0, -1, width, height); break;
      case 4: ctx.transform(1, 0, 0, -1, 0, height); break;
      case 5: ctx.transform(0, 1, 1, 0, 0, 0); break;
      case 6: ctx.transform(0, 1, -1, 0, height, 0); break;
      case 7: ctx.transform(0, -1, -1, 0, height, width); break;
      case 8: ctx.transform(0, -1, 1, 0, 0, width); break;
      default: break;
    }

    // draw image
    ctx.drawImage(img, 0, 0);

    // export base64
    callback(canvas.toDataURL());
  };

  img.src = srcBase64;
};