SilverStripe 3.1.x Auto-rotate mobile images on upload according to EXIF Orientation data

SS-rotate-mobile-image-extension.php

<?php

/**
 * Image Extension
 */

class ImageExtension extends DataExtension {

	// Rotated Image - 
	// Some mobile image when uploaded will appear correctly oriented on mobile devices, but when 
	// viewed on a desktop will appear oriented the wrong way up. 
	
	public function RotatedImage($angle) {
		return $this->owner->getFormattedImage('RotatedImage', $angle);
	}
	
	public function generateRotatedImage(GD $gd, $angle) {
		return $gd->rotate($angle);
	}
	

	/**
	 * Mobile image correction
	 */
	
	public function onAfterUpload() {
		
		$self = $this->owner;
		
		if ($file = $self->getField('Filename')) {
			
			// image path & exif metadata
			$imagePath = $self->getFullPath();
			$type = strtolower(File::get_file_extension($imagePath));
			
			if ($type == "jpeg" || $type == "jpg") {
			
				$exif = exif_read_data($imagePath);
				
				// resource optimisation
				if (file_exists($imagePath) && !empty($exif['Orientation'])) {
					
					// only JPEG has metadata, so no PNG or GIF parsers necessary
					$source = imagecreatefromjpeg($imagePath);
					
					// modify according to orientation
					// replace jpeg at source, thus no other complexities regarding renaming, etc.
					// image write placed inline for further resource optimisation
					switch ($exif['Orientation']) {
						case 3 :
							$image = imagerotate($source, 180, 0);
							imagejpeg($image, $imagePath, 100);
							break;
						case 6 :
							$image = imagerotate($source, -90, 0);
							imagejpeg($image, $imagePath, 100);
							break;
						case 8 :
							$image = imagerotate($source, 90, 0);
							imagejpeg($image, $imagePath, 100);
							break;
					}
					
				}
				
			}
		}
		
		// inherited from "owner"
		$self->deleteFormattedImages();
		
	}

}

Requires appropriate entry in the _config/config.yml file. For example, if the above snippet is saved in a file called ImageExtension.php, the following must be added to the yaml file:

Image:
  extensions:
    - 'ImageExtension'