在我们的工作的项目中，有时候我们需要显示规定尺寸的图片，虽然可以通过css来控制显示大小。但是如果图片过大，会造成加载的延迟，影响网站整体性能。因此，我们需要一个服务器来帮助我们进行图片的裁剪。流程大致是，首先我们传给服务器原图像和裁剪的尺寸，然后服务器进行裁剪，生成对应的裁剪图片，下次我们再访问相同图像和相同的裁剪尺寸的时候，我们就不需要裁剪，直接进行图片的访问就行。

Talk is cheap, show me the code.

<?php

// ①构建图片请求地址比如  http://xxx.com/resize.php?site=www&width=300&height=200&mode=2&path=uploadfile/helloworld.png

// ②配置nginx重写规则  rewrite /s/(.)/(\d+)x(\d+)-(\d)/(.) /s/resize.php?site=$1&width=$2&height=$3&mode=$4&path=$5 last;

//③进行裁剪图片的处理

$path = trim($_GET[‘path’]);

$mode = intval($_GET[‘mode’]);

$site = trim($_GET[‘site’]);

$width = intval($_GET[‘width’]);

$height = intval($_GET[‘height’]);

$site_list = array(‘crop’ => ‘.’);

$orig_dir = dirname(FILE);

if (!array_key_exists($site, $site_list)) {

header(‘HTTP/1.1 400 Bad Request’);

exit();

}

if ($mode > 3 || $mode < 0) {

header(‘HTTP/1.1 400 Bad Request’);

exit();

}

$orig_file = $site_list[$site] . $path;

if (!file_exists($orig_file)) {

header(‘HTTP/1.1 404 Not Found’);

exit();

}

$file_ext = ‘.’ . pathinfo($path, PATHINFO_EXTENSION);

$file_name = basename($path, $file_ext);

$save_path = “{$orig_dir}/{$site}/{$width}x{$height}-{$mode}{$path}”;

$save_dir = dirname($save_path);

if (!file_exists($save_dir)) {

wpx_mkdir($save_dir);

}

$target_width = $width;

$target_height = $height;

$save_image = $save_dir . ‘/’ . $file_name . ‘.jpg’;

if (file_exists($save_image)) {

header(‘Content-Type: image/jpeg’);

header(‘Last-Modified: ’ . gmdate(‘D, d M Y H:i:s’) . ’ GMT’);

echo file_get_contents($save_image);

}

imagecropper2($orig_file, $target_width, $target_height, $save_image);

die;

//原图像对应缩放裁剪，会拉伸图片

function imagecropper2($source_path, $width, $height, $save_image)

{

//获取原图像$filename的宽度$width_orig和高度$height_orig

$info =  getimagesize($source_path);

$width_orig = $info[0];

$height_orig = $info[1];

$mime = $info[‘mime’];

//根据参数$width和$height值，换算出等比例缩放的高度和宽度

if ($width && ($width_orig<$height_orig)){

$width = ($height/$height_orig)*$width_orig;

}else{

$height = ($width / $width_orig)*$height_orig;

}

//将原图缩放到这个新创建的图片资源中

$image_p = imagecreatetruecolor($width, $height);

//获取原图的图像资源

if($mime==‘image/jpeg’){

$image = imagecreatefromjpeg($source_path);

}elseif($mime==‘image/png’){

$image = imagecreatefrompng($source_path);

}elseif($mime==‘image/gif’){

$image = imagecreatefromgif($source_path);

}

//使用imagecopyresampled()函数进行缩放设置

imagecopyresampled($image_p,$image,0,0,0,0,$width,$height,$width_orig,$height_orig);

//将缩放后的图片$image_p保存，100(质量最佳，文件最大)

if($mime==‘image/jpeg’){

imagejpeg($image_p,$save_image);

header(‘Content-Type: image/jpeg’);

imagejpeg($image_p);

}elseif($mime==‘image/png’){

imagepng($image_p,$save_image);

header(‘Content-Type: image/jpeg’);

imagepng($image_p);

}else{

imagegif($image_p,$save_image);

header(‘Content-Type: image/jpeg’);

imagegif($image_p);

}

}

//进行比例保存裁剪，会丢失图像部分像素

function imagecropper($source_path, $target_width, $target_height, $save_image)

{

$source_info = getimagesize($source_path);

$source_width = $source_info[0];

$source_height = $source_info[1];

$source_mime = $source_info[‘mime’];

$source_ratio = $source_height / $source_width;

$target_ratio = $target_height / $target_width;

// 源图过高

if ($source_ratio > $target_ratio) {

$cropped_width = $source_width;

$cropped_height = $source_width * $target_ratio;

$source_x = 0;

$source_y = ($source_height – $cropped_height) / 2;

}

// 源图过宽

elseif ($source_ratio < $target_ratio) {

$cropped_width = $source_height / $target_ratio;

$cropped_height = $source_height;

$source_x = ($source_width – $cropped_width) / 2;

$source_y = 0;

}

// 源图适中

else {

$cropped_width = $source_width;

$cropped_height = $source_height;

$source_x = 0;

$source_y = 0;

}

switch ($source_mime) {

case ‘image/gif’:

$source_image = imagecreatefromgif($source_path);

break;

case ‘image/jpeg’:

$source_image = imagecreatefromjpeg($source_path);

break;

case ‘image/png’:

$source_image = imagecreatefrompng($source_path);

break;

default:

return false;

break;

}

$target_image = imagecreatetruecolor($target_width, $target_height);

$cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);

// 裁剪

$bool = imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);

// 缩放

$bool = imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);

imagejpeg($target_image, $save_image);

header(‘Content-Type: image/jpeg’);

imagejpeg($target_image);

imagedestroy($source_image);

imagedestroy($target_image);

imagedestroy($cropped_image);

}

// 循环生成目录

function wpx_mkdir($dir, $mode = 0777)

{

if (is_dir($dir) || @mkdir($dir, $mode)) {

return true;

}

if (!wpx_mkdir(dirname($dir), $mode)) {

return false;

}

return @mkdir($dir, $mode);

}

通过上面的处理，我们就将图片按照我们设置的尺寸进行了裁剪。我们还可以定期对裁剪图片进行清理，这样就不需要占用太多服务器空间。只有经常访问的图片才会一直保存。