How to extract focus information from a photo using PHP and Exif extension

How to use PHP and Exif extensions to extract focus information from photos

Photography is a popular art form, and we often share the photos we take on social media. However, what we really care about is how to take our photos to be more professional and clear. One important factor is focal information. Focus information refers to the subject in the photo that is selected by the camera's automatic focus. In this article, we will use PHP and the Exif extension to extract the focus information of a photo.

First, we need to make sure that PHP and Exif extensions are installed on the server. The Exif extension is an extension for PHP that can be used to read Exif metadata contained in JPEG and TIFF type images.

Once we make sure that the Exif extension is installed, we can use the following code to extract the focus information of the photo:

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

// 使用exif_read_data函数读取照片的Exif元数据
$exif = exif_read_data($photoPath);

// 判断照片是否包含焦点信息
if(isset($exif['FocalLength'])){
    // 提取焦点信息
    $focalLength = $exif['FocalLength'];
    echo "焦距: ".$focalLength." mm";
} else {
    echo "照片中没有焦点信息";
}
?>

In the above code, we first specify the path to the photo that we want to analyze. We then use the exif_read_data function to read the photo’s Exif metadata. If the photo contains focus information, we extract the focus information from the metadata and output it. Otherwise, we output a corresponding message.

Please note that focus information is usually given in millimeters (mm).

To better understand the meaning of focus information, let us consider the following two examples:

Example 1:
Focal length: 50mm
This means that the photo was taken using a 50mm Photographed with a focal length lens. A shorter focal length (such as 35mm) indicates that the lens has a wide angle, while a longer focal length (such as 200mm) indicates that the lens has telephoto capabilities. Choosing the appropriate focal length can make your subject appear clearer.

Example 2:
Focal length: 18-55mm
This means that the camera is using a zoom lens. The range of focal lengths can be adjusted as desired, changing the size and sharpness of your chosen subject.

By extracting focus information from a photo, we can better understand how the photo was taken and use this information to improve our own photography skills. We can choose the appropriate focal length to highlight the subject and get clearer photos.

Summary:
This article introduces how to use PHP and Exif extensions to extract focus information from photos. By reading a photo's Exif metadata and extracting focus information from it, we can better understand how the photo was taken. Knowing this information can help us choose the right focal length to take clearer and more professional-looking photos. I hope readers can improve their photography skills through the content of this article.

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