How to read the focus distance of a photo using PHP and Exif extension

How to read the focus distance of a photo using PHP and Exif extensions

Photography is an art that pays attention to details, and focus distance is an important parameter in photography. In digital photography, each picture contains EXIF ​​(Exchangeable Image File Format) metadata about the photo. Using PHP and Exif extensions, we can easily read the focus distance information of a photo.

First, make sure your PHP environment has the Exif extension installed. You can enable it in the php.ini file, or install it directly using the following command line:

$ sudo apt-get install php7.4-exif

Next, let’s try to read the focus distance information of the photo. Suppose we have an image called "photo.jpg", we will use the following code:

<?php
// 图片路径
$photoPath = 'photo.jpg';

// 读取照片的Exif信息
$exif = exif_read_data($photoPath, 0, true);

// 获取焦点距离
if(isset($exif['EXIF']['FocalLength'])){
    $focalLength = $exif['EXIF']['FocalLength'];
    echo "焦点距离：" . $focalLength . "mm";
} else {
    echo "无法获取焦点距离信息。";
}
?>

In the code, we first specify the path to the photo. Then, we use the exif_read_data() function to read the Exif information of the photo, passing 0 and true as parameters. This will return an array containing all the Exif data.

Next, we check if the EXIF['FocalLength'] key exists. If it exists, we will get the focus distance value and print it out. Otherwise, we will output the message that the focus distance information cannot be obtained.

To run this code, save it as a PHP file and run it from the command line:

$ php get_focal_length.php

If all goes well, you will see the focus distance of the photo printed in the output .

It should be noted that the focus distance is usually expressed in millimeters (mm). For different photos, there may be different types of focus distance values, such as fixed focus lenses (such as 50mm) or zoom lenses (such as 18-55mm).

Additionally, sometimes the focus distance information for a photo may not exist or be available. In this case, we need to have proper error handling in our code to ensure that our application doesn't crash due to the inability to get the focus distance.

To sum up, using PHP and Exif extensions, we can easily read the focus distance information of photos. This gives us more flexibility and functionality in photography applications, image processing and data analysis. This skill will be extremely useful whether you are working in the photography industry or as a developer interested in image data.

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