PHP and Exif: How to get the zoom information of a photo

PHP and Exif: How to get the zoom ratio information of a photo

The zoom ratio of a photographic work is an important metadata that can tell us whether the image has been modified or resized. In PHP, you can get the photo scaling information through the Exif extension. This article will introduce how to use PHP and Exif extensions to obtain the zoom ratio information of photos, and provide corresponding code examples.

1. What is Exif?

Exif (Exchangeable image file format) is a metadata format used to store digital photos. It can contain a lot of information about the photo, such as the time it was taken, camera model, focal length, aperture, exposure time, etc. This also includes image scaling information.

2. Use the Exif extension to obtain scaling information

In PHP, you can use the Exif extension to read the Exif data of the photo. First make sure the Exif extension is installed and enabled. You can enable the Exif extension by setting "exif.enable" in the php.ini file, or use the function extension_loaded('exif') to check whether the extension is loaded.

The following is a simple PHP code example that shows how to use the Exif extension to obtain the zoom ratio information of the photo:

// 读取照片的Exif数据
$exif = exif_read_data('photo.jpg');

if(isset($exif['COMPUTED']['Width']) && isset($exif['COMPUTED']['Height'])){
    // 计算缩放比例
    $width = $exif['COMPUTED']['Width'];
    $height = $exif['COMPUTED']['Height'];
    $ratio = $width / $height;

    echo "照片的缩放比例为：$ratio";
} else {
    echo "无法获取照片的缩放比例信息";
}

In the above code, we first use exif_read_data()The function reads the Exif data of the photo and stores it in the variable $exif. We then check if the "COMPUTED" key exists in the $exif array, and if the "Width" and "Height" keys exist under that key. If present, we can obtain the scaling by calculating the ratio between width and height. Finally, we output the scaling to the browser.

It should be noted that the exif_read_data() function is only used to read the Exif data of photos in JPEG format. If you need to read photos in other formats, you can use other functions to read the corresponding Exif data.

3. Summary

In photography works, scaling information can help us understand whether the photo has been modified or resized. Using PHP and Exif extensions, we can easily get the zoom information of a photo. This article provides a simple code example that shows how to use the Exif extension to obtain the zoom information of a photo. I hope this article helps you understand how to get zoom information for a photo.

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