How to detect shot angle of photo, and auto rotate for website display like desktop apps do on viewing?

Question

If I take a photo with a camera it stores the orientation/angle of the apparatus so when I view the image on the PC with a good app, it shows auto-rotated to 0.

But when I upload to a website it shows the original angle, so the image doesn't look good.

How can I detect this with PHP and rotate the image, and clear this angle flag from it's meta information.

Answer 1

The rotation flag is stored as part of the EXIF data (see this article for more info).

You will need to read the rotation flag from the EXIF data in PHP and then rotate the image to suit. There are a variety of PHP EXIF libraries, if you have the web server set up with the extension installed you would be able to use the PHP provided library.

I would suggest rotating the image once on upload (e.g. using the GD library - most PHP installations these days seem to come with it), so that you don't need to worry about clearing the EXIF rotation data (not sure how easy this is with PHP, I've never tried it).

Answer 2

In order to do that, you must read the EXIF information out of the JPEG file. You can either do that with exif PHP extension or with PEL.

Basically, you have to read the Orientation flag in the file. Here is an example using the exif PHP extension and WideImage for image manipulation.

<?php
$exif = exif_read_data($filename);
$ort = $exif['Orientation'];

$image = WideImage::load($filename);

// GD doesn't support EXIF, so all information is removed.
$image->exifOrient($ort)->saveToFile($filename);

class WideImage_Operation_ExifOrient
{
  /**
   * Rotates and mirrors and image properly based on current orientation value
   *
   * @param WideImage_Image $img
   * @param int $orientation
   * @return WideImage_Image
   */
  function execute($img, $orientation)
  {
    switch ($orientation) {
      case 2:
        return $img->mirror();
        break;

      case 3:
        return $img->rotate(180);
        break;

      case 4:
        return $img->rotate(180)->mirror();
        break;

      case 5:
        return $img->rotate(90)->mirror();
        break;

      case 6:
        return $img->rotate(90);
        break;

      case 7:
        return $img->rotate(-90)->mirror();
        break;

      case 8:
        return $img->rotate(-90);
        break;

      default: return $img->copy();
    }
  }
}