php 抓取网页生成图片(php实现网站图片尺寸重写时，默认情况下浏览器不会将重写的图片数据 )

　　php 抓取网页生成图片(php实现网站图片尺寸重写时，默认情况下浏览器不会将重写的图片数据

)

　　当我们使用php实现网站图片大小重写时，浏览器默认不会在本地缓存重写后的图片。现在我将告诉你如何让浏览器缓存这样的图像数据。

　　// 将以下代码添加到 php 脚本文件中

　　session_start();

header("Cache-Control: private, max-age=10800, pre-check=10800");

header("Pragma: private");

header("Expires: " . date(DATE_RFC822,strtotime(" 2 day")));

　　1：如果浏览器已经有缓存版本，它会向后端传递一个$_SERVER['HTTP_IF_MODIFIED_SINCE']。简单来说，我们只需要告诉浏览器使用缓存即可。

　　if(isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])){

// if the browser has a cached version of this image, send 304

header('Last-Modified: '.$_SERVER['HTTP_IF_MODIFIED_SINCE'],true,304);

exit;

}

　　2：如果浏览器有缓存版本，更明智的做法是后端判断图片是否已经更新，并据此通知浏览器是否使用缓存版本

　　$img = "some_image.png";

if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])

&&

(strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == filemtime($img))) {

// send the last mod time of the file back

header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($img)).' GMT',

true, 304);

exit;

}

　　完整代码

　　session_start();

header("Cache-Control: private, max-age=10800, pre-check=10800");

header("Pragma: private");

header("Expires: " . date(DATE_RFC822,strtotime(" 2 day")));

$img = "some_image.png";

if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])

&&

(strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == filemtime($img))) {

// send the last mod time of the file back

header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($img)).' GMT',

true, 304);

exit;

}

　　// 裁剪图片并告诉浏览器缓存图片

　　$is = new ImageSizer($img);

$is->resizeImage(75); // resize image to 75px wide

// and here we send the image to the browser with all the stuff required for tell it to cache

header("Content-type: image/jpeg");

header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime($thumbnail)) . ' GMT');

$is->showImage();

　　图像裁剪类

　　class ImageSizer {

var $_baseDir;

var $_baseImg;

var $_imgData;

var $_newImg;

var $_newData;

var $_newFormat;

var $_loadPath;

var $_defaultColor = array(255,255,255);

var $keepAspectRatio;

var $makeBigger;

function ImageSizer($baseDir) {

$this->changeBaseDir($baseDir);

$this->keepAspectRatio = true;

$this->makeBigger = false;

}

function changeBaseDir($baseDir) {

$this->_baseDir = $baseDir;

}

function setDefaultColor($r, $g, $b) {

$this->_defaultColor = array($r, $g, $b);

}

function changeFormat($str) {

$str = strtolower($str);

if ($str == 'jpg') $str = "jpeg";

$acceptable_formats = array('jpeg', 'gif', 'png');

if (!in_array($str, $acceptable_formats)) return false;

$this->_newFormat = $str;

}

function loadImage($imgPath) {

// $this->_imgData = getimagesize($this->_baseDir. $imgPath);

$this->_imgData = getimagesize( $imgPath);

$this->_imgData['funcType'] = preg_replace('#image/#i', '', $this->_imgData['mime']);

$acceptable_formats = array('jpeg', 'gif', 'png');

if (!in_array($this->_imgData['funcType'], $acceptable_formats)) return false;

$this->_newData = $this->_imgData;

$funcName = 'imagecreatefrom' . $this->_imgData['funcType'];

//$this->_newImg = $this->_baseImg = $funcName($this->_baseDir. $imgPath);

$this->_newImg = $this->_baseImg = @$funcName( $imgPath);

if(!$this->_baseImg){

echo "

Failed on this image $imgPath

";

return false;

}

$this->_loadPath = $imgPath;

return true;

}

/*function genImageData(){

$funcName = 'image'.$this->getNewType();

$data = $funcName($this->_newImg ? $this->_newImg : $this->_baseImg);

return $data;

}*/

function resizeImage($w, $h, $crop=false) {

$current_w = $this->getWidth();

$current_h = $this->getHeight();

$src_x = $src_y = 0;

$dst_x = $dst_y = 0;

if($w && $h && $crop=="f"){

// fill in the image centre it in white.

// all the src stuff stays the same, just changing the destination suff

$src_x = 0;

$src_y = 0;

$current_h = $current_h;

$current_w = $current_w;

// the destination stuff changes

if($h && $w){

$h_percent = $percent = $h / $current_h;

$w_percent = $percent = $w / $current_w;

$percent = min($h_percent, $w_percent);

}else if($h){

$h_percent = $percent = $h / $current_h;

$percent = $h_percent;

}else if($w){

$w_percent = $percent = $w / $current_w;

$percent = $w_percent;

}

$dst_w = $current_w * $percent;

$dst_h = $current_h * $percent;

$new_w = $w;

$new_h = $h;

// work out destination x and y points

$dst_x = ($new_w - $dst_w)/2;

$dst_y = ($new_h - $dst_h)/2;

}else if($w && $h && $crop=="c"){

$dst_w = $w;

$dst_h = $h;

$new_w = $w;

$new_h = $h;

// if the image we are tyring to crop is smaller than the crop request we dont do aynthing

if($w > $current_w || $h > $current_h){

// the image is smaller than we are trying to crop!

}else{

//the image is bigger on x and y axis.

// check if we can fit horizontally

$w_percent = $current_w/$w;

$h_percent = $current_h/$h;

if($w_percent < $h_percent){

$src_x = 0;

$src_y = ($current_h/2) - (($h * $w_percent)/2);

$current_w = $current_w;

$current_h = ($h * $w_percent);

}else{

$src_x = ($current_w/2) - (($w * $h_percent)/2);

$src_y = 0;

$current_w = ($w * $h_percent);

$current_h = $current_h;

}

}

}else if ($this->keepAspectRatio) {

$percent = 1;

// if ($current_w > $w || $current_h > $h || $this->makeBigger) {

$do_resize=false;

if($w && $current_w > $w){

$do_resize=true;

}else if($h && $current_h > $h){

$do_resize=true;

}else if($w && $current_w < $w && $this->makeBigger){

$do_resize=true;

}else{

// imaeg is alreaedy smaller than requested size

}

if ( $do_resize ) {

if($h && $w){

$h_percent = $percent = $h / $current_h;

$w_percent = $percent = $w / $current_w;

$percent = min($h_percent, $w_percent);

}else if($h){

$h_percent = $percent = $h / $current_h;

$percent = $h_percent;

}else if($w){

$w_percent = $percent = $w / $current_w;

$percent = $w_percent;

}

}

$dst_w = $new_w = $current_w * $percent;

$dst_h = $new_h = $current_h * $percent;

} else{

$dst_w = $new_w = $w;

$dst_h = $new_h = $h;

}

$this->_newImg = ImageCreateTrueColor($new_w, $new_h);

$this->_newData = array($new_w, $new_h);

if ($this->getNewType() == &#39;png&#39; || $this->getNewType() == &#39;gif&#39;) { // This preserves the transparency

imageAlphaBlending($this->_newImg, false);

imageSaveAlpha($this->_newImg, true);

} else { // This is if converting from PNG to another image format

list($r, $g, $b) = $this->_defaultColor;

$color = imagecolorallocate($this->_newImg, $r, $g, $b);

imagefilledrectangle($this->_newImg, 0,0, $new_w, $new_h, $color);

}

// dst_w dst_h src_w src_h

imagecopyresampled($this->_newImg, $this->_baseImg, $dst_x, $dst_y,$src_x,$src_y, $dst_w, $dst_h, $current_w, $current_h);

return true;

}

function showImage() {

header(&#39;Content-type: &#39; . $this->getNewMime());

$funcName = &#39;image&#39;.$this->getNewType();

$funcName($this->_newImg ? $this->_newImg : $this->_baseImg);

}

function saveToFile($fileloc) {

$funcName = &#39;image&#39;.$this->getNewType();

$funcName($this->_newImg ? $this->_newImg : $this->_baseImg, $fileloc,100);

}

function addWatermark($pngloc,$offset_x=0) {

$overlay = imagecreatefrompng($pngloc);

imageAlphaBlending($overlay, false);

imageSaveAlpha($overlay, true);

imagecopy($this->_newImg, $overlay, (imagesx($this->_newImg))-(imagesx($overlay)+$offset_x), (imagesy($this->_newImg))-(imagesy($overlay)), 0, 0, imagesx($overlay), imagesy($overlay));

}

function getBaseDir() { return $this->_baseDir; }

function getWidth() { return $this->_imgData[0]; }

function getHeight() { return $this->_imgData[1]; }

function getMime() { return $this->_imgData[&#39;mime&#39;]; }

function getType() { return $this->_imgData[&#39;funcType&#39;];}

function getNewWidth() { return $this->_newData[0]; }

function getNewHeight() { return $this->_newData[1]; }

function getNewMime() {return $this->_newFormat ? &#39;image/&#39; . $this->_newFormat : $this->_imgData[&#39;mime&#39;];}

function getNewType() {return $this->_newFormat ? $this->_newFormat : $this->_imgData[&#39;funcType&#39;];}

}