我有一个动态缩略图脚本，我在网上找到并稍作调整。我添加的其中一件事是缓存机制。每当生成新的缩略图时，它都会保存到磁盘，如果再次请求相同的缩略图（具有所有相同的选项），则将使用磁盘副本。
一个片段：
// name of cached file
$thumb_file = $_SERVER['DOCUMENT_ROOT'].'/thumbs/cache/'.
str_replace('/', '_', $_REQUEST['p']).
".{$def_width}x{$def_height}".
($clamp ? '_'.implode('x',$clamp) : '').
($make_png?'.png':'.jpg');
// get it from cache if it's there
if ($use_cache && file_exists($thumb_file)) {
Header("Content-type: image/".($make_png?'png':'jpeg'));
// this part seems really slow
$fp=fopen($thumb_file, "rb");
while (!feof($fp)) print fread($fp, 4096);
exit();
}
但是，print结果fread似乎很慢，有时（很少）图像没有完全加载。
那么，我怎样才能加快速度呢？我应该将浏览器重定向到图像而不是freading 它，还是有其他选择？
我在下面包含了完整的 PHP 脚本，以防万一。
<?php
$use_cache = $_REQUEST['nc'] ? false : true;
// $use_cache = false;
$upfile = $_SERVER['DOCUMENT_ROOT'] .'/'. $_REQUEST['p'];
$def_width = $_REQUEST["w"];
$def_height = $_REQUEST["h"];
$clamp = $_REQUEST['c'] ? explode("x",$_REQUEST['c']) : null;
$make_png = $_REQUEST['png'];
if (!file_exists($upfile)) {
die(); // $upfile = "nophoto.jpg";
}
if (!"{$def_width}{$def_height}") {
$def_width = $def_height = '100';
}
// name of cached file
$thumb_file = $_SERVER['DOCUMENT_ROOT'].'/thumbs/cache/'.
str_replace('/', '_', $_REQUEST['p']).
".{$def_width}x{$def_height}".
($clamp ? '_'.implode('x',$clamp) : '').
($make_png?'.png':'.jpg');
// get it from cache if it's there
if ($use_cache && file_exists($thumb_file)) {
Header("Content-type: image/".($make_png?'png':'jpeg'));
$fp=fopen($thumb_file, "rb");
while (!feof($fp)) print fread($fp, 4096);
exit();
}
$ext = strtolower(substr($upfile, -3));
ini_set('memory_limit', '64M');
if ($ext=="gif")
$src = @ImageCreateFromGif ($upfile);
else if ($ext=="jpg")
$src = @ImageCreateFromJpeg($upfile);
else if ($ext=="png")
$src = @ImageCreateFromPng($upfile);
$size = GetImageSize($upfile);
$width = $size[0];
$height = $size[1];
$long_side = $def_width;
if ($def_width < $def_height) $long_side = $def_height;
if (!$def_width) {
$factor_h = $height / $def_height;
$def_width = $width / $factor_h;
}
if (!$def_height) {
$factor_w = $width / $def_width;
$def_height = $height / $factor_w;
}
$factor_w = $width / $def_width;
$factor_h = $height / $def_height;
if ($factor_w > $factor_h) {
$new_height = floor($def_height * $factor_h);
$new_width = floor($def_width * $factor_h);
} else {
$new_height = floor($def_height * $factor_w);
$new_width = floor($def_width * $factor_w);
}
if ((!$clamp[0])&&$clamp[0]!=='0') $clamp[0] = 50;
if ((!$clamp[1])&&$clamp[1]!=='0') $clamp[1] = 50;
$src_x = ceil(($width - $new_width) * ($clamp[0] / 100));
$src_y = ceil(($height - $new_height) * ($clamp[1] / 100));
$dst = ImageCreateTrueColor($def_width, $def_height);
@ImageCopyResampled($dst, $src, 0, 0, $src_x, $src_y,
$def_width, $def_height, $new_width, $new_height);
Header("Content-type: image/".($make_png?'png':'jpeg'));
if ($make_png) {
ImagePng($dst);
if ($use_cache) {
ImagePng($dst, $thumb_file);
}
} else {
ImageJpeg($dst, null, 95);
if ($use_cache) {
ImageJpeg($dst, $thumb_file, 95);
}
}
@ImageDestroy($src);
@ImageDestroy($dst);
?>