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。

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