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本文档使用 PHP中文网手册 发布
(PHP 5 >= 5.5.0, PHP 7)
imagewebp — 将 WebP 格式的图像输出到浏览器或文件
$image
, string $filename
)
将 image
参数指定的图像以 WebP 格式输出到浏览器或者保存到文件。
image
由图象创建函数(例如 imagecreatetruecolor() )返回的图象资源。
filename
文件保存的路径,如果未设置或为 NULL
,将会直接输出原始图象流。
成功时返回 TRUE
, 或者在失败时返回 FALSE
。
Example #1 保存为 WebP 图像文件
<?php
// 创建一个空图像并在其上加入一些文字
$im = imagecreatetruecolor ( 120 , 20 );
$text_color = imagecolorallocate ( $im , 233 , 14 , 91 );
imagestring ( $im , 1 , 5 , 5 , 'WebP with PHP' , $text_color );
// 保存图像
imagewebp ( $im , 'php.webp' );
// 释放内存
imagedestroy ( $im );
?>
[#1] mauro dot ludovico dot colella at gmail dot com [2015-02-12 06:41:05]
It is also possible to defer the creation of png replacements for WebP images to the client, with notably the library libwebpjs enabling transparent conversion.
[#2] orangefish at sogetthis dot com [2013-06-25 23:32:23]
WebP is a great file format, but it's basically supported only by Chrome. For WebP files with transparency it's necessary to have PNG fallback for other browsers (otherwise it won't work in iOS, Firefox, IE, etc.).
Regular truecolor PNG with alpha gives pretty large files, but there's a special smaller PNG file variant that can be created by pngquant - a command line utility.
If you have pngquant 1.8 on your server (just get package from official pngquant website), then you can create small fallback images (with quality better than from PHP's libgd):
<?php
function compress_png($path_to_png_file, $max_quality = 90)
{
if (!file_exists($path_to_png_file)) {
throw new Exception("File does not exist: $path_to_png_file");
}
// guarantee that quality won't be worse than that.
$min_quality = 60;
// '-' makes it use stdout, required to save to $compressed_png_content variable
// '<' makes it read from the given file path
// escapeshellarg() makes this safe to use with any path
$compressed_png_content = shell_exec("pngquant --quality=$min_quality-$max_quality - < ".escapeshellarg( $path_to_png_file));
if (!$compressed_png_content) {
throw new Exception("Conversion to compressed PNG failed. Is pngquant 1.8+ installed on the server?");
}
return $compressed_png_content;
}
?>
So for example when user is uploading a PNG file:
<?php
$read_from_path = $_FILE['file']['tmp_name'];
$save_to_path = "uploads/compressed_file.png";
$compressed_png_content = compress_png($read_from_path);
file_put_contents($save_to_path, $compressed_png_content);
// you don't need move_uploaded_file().
// and for webp:
imagewebp(imagecreatefrompng($read_from_path), $save_to_path + ".webp");
?>
And then you can use URL with .webp version in Chrome and browsers that send Accept: image/webp, and .png for the rest (and all will get small file!)