How to extract the rotation angle of a photo using PHP and Exif extension

How to use PHP and Exif extensions to extract the rotation angle of a photo

In modern camera equipment, photos usually have a rotation angle attribute. Since some devices automatically rotate photos after taking them, sometimes we need to extract the rotation angle of the photo to ensure that the photo is displayed correctly. In this article, we will explain how to extract the rotation angle of a photo using PHP and the Exif extension.

First, we need to ensure that PHP’s Exif extension is enabled on the server. In most cases, this extension is already enabled by default. We can check whether the extension is enabled in the PHP configuration file. Here is a code example to see if the extension is enabled:

<?php
phpinfo();
?>

Save the above code as phpinfo.php and access the file through your browser. In the output information, we can search for "Exif" to see whether the Exif extension is enabled.

Next, we need to obtain the rotation angle information of the photo. In PHP, we can obtain the EXIF ​​data of the photo through the exif_read_data() function. The following is a code example for reading the rotation angle of a photo:

<?php
// 获取照片的EXIF数据
$exif = exif_read_data('path/to/photo.jpg');

// 检查旋转信息是否存在
if(isset($exif['Orientation'])){
  // 获取旋转角度
  $orientation = $exif['Orientation'];

  // 根据旋转角度进行相应操作
  switch($orientation){
    case 3:
      // 180度旋转
      echo "照片需旋转180度";
      break;
    case 6:
      // 顺时针旋转90度
      echo "照片需顺时针旋转90度";
      break;
    case 8:
      // 逆时针旋转90度
      echo "照片需逆时针旋转90度";
      break;
    default:
      // 无需旋转
      echo "照片无需旋转";
      break;
  }
}
?>

In the above example, we first use the exif_read_data() function to read the EXIF ​​data of the photo and assign it to the variable $exif. Then, we check whether the rotation angle information exists in the variable $exif. If it exists, we use the switch statement to determine the value of the rotation angle, and output corresponding prompt information according to the different values.

Please note that different devices may use different values ​​to represent rotation angles. Some common rotation angle values ​​include: 1 (no rotation), 3 (rotation 180 degrees), 6 (rotation 90 degrees clockwise), and 8 (rotation 90 degrees counterclockwise). If you need more detailed information, please refer to the photo's EXIF ​​specification.

Finally, depending on the rotation angle of the photo, you can use the corresponding method to rotate the photo or take other operations. It depends on the graphics processing library or tool you use.

To summarize, it is very simple to extract the rotation angle of a photo using PHP and the Exif extension. By using the exif_read_data() function to read the EXIF ​​data of the photo and perform corresponding operations based on the value of the rotation angle, we can ensure that the photo is displayed correctly.

The above is the detailed content of How to extract the rotation angle of a photo using PHP and Exif extension. For more information, please follow other related articles on the PHP Chinese website!