PHP and Exif: How to get lens focal length range information for a photo

PHP and Exif: How to obtain the lens focal length range information of a photo

Photography enthusiasts are always curious about the shooting parameters of photos, among which the lens focal length range is a very important one. For photography enthusiasts, understanding the lens focal length range of a photo can help them better understand the specific effects and shooting angles of the photo. When using PHP to process photos, we can use Exif (Exchangeable Image File Format) to obtain relevant information about the photo, including the lens focal length range. This article will introduce how to use PHP to obtain the lens focal length range information of a photo.

First of all, we need to make sure that the exif extension has been installed on the server. You can check it by executing the following command:

php -m | grep exif

If exif is returned, it means that exif has been installed Extension. If it is not installed, you can refer to the official PHP documentation or use the package manager for your operating system to install it.

In PHP, we can use the exif_read_data function to read the Exif information of the photo. The use of this function is as follows:

$exif = exif_read_data('photo.jpg');

where photo.jpg is the path of the photo to be read. After successful reading, the $exif variable will contain the Exif information of the photo.

Next, we need to find the Exif tag of the lens focal length range. In Exif, lens focal length range information is usually stored in the FocalLength tag. We can get the lens focal length range in the following way:

$focalLength = $exif['FocalLength'];

$focalLengthThe variable will contain the lens focal length range of the photo, expressed in the form of a string. For example, if the lens focal length range is 24mm to 105mm, the value of $focalLength will be 24/105. According to actual needs, we can further parse the string and extract the specific focal length range.

The following is a complete sample code that demonstrates how to obtain the lens focal length range information of a photo:

<?php
// 读取照片的Exif信息
$exif = exif_read_data('photo.jpg');

// 获取焦距范围
$focalLength = $exif['FocalLength'];

// 解析焦距范围
$focalLengthArr = explode('/', $focalLength);
$minFocalLength = $focalLengthArr[0];
$maxFocalLength = $focalLengthArr[1];

// 输出结果
echo "最小焦距：{$minFocalLength}mm
";
echo "最大焦距：{$maxFocalLength}mm
";
?>

In this example, we first read it through the exif_read_data function Get the Exif information of the photo, and then use the explode function to split the focal length range string into minimum focal length and maximum focal length. Finally, we output the results to the screen.

It should be noted that since different brands and models of cameras may store Exif information differently, in actual use, we need to parse the Exif information according to the specific camera model. You can obtain the Exif parsing rules related to the camera model by consulting the camera's official documentation or third-party libraries.

Summary:

PHP and Exif provide convenient solutions for obtaining lens focal length range information of photos. By using the exif_read_data function and parsing the Exif tag, we can easily obtain the lens focal length range of the photo. This is very useful for photography enthusiasts and can help them better understand the shooting parameters and effects of photos.

We hope that the introduction and sample code of this article can help readers understand how to use PHP to obtain the lens focal length range information of photos and bring its value into practical applications.

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