php 图片压缩

方法一、

http://www.codefans.net/articles/99.shtml

function img_create_small($big_img, $width, $height, $small_img) {//原始大图地址，缩略图宽度，高度，缩略图地址
$imgage = getimagesize($big_img); //得到原始大图片
switch ($imgage[2]) { // 图像类型判断
case 1:
$im = imagecreatefromgif($big_img);
break;
case 2:
$im = imagecreatefromjpeg($big_img);
break;
case 3:
$im = imagecreatefrompng($big_img);
break;
}
$src_W = $imgage[0]; //获取大图片宽度
$src_H = $imgage[1]; //获取大图片高度
$tn = imagecreatetruecolor($width, $height); //创建缩略图
imagecopyresampled($tn, $im, 0, 0, 0, 0, $width, $height, $src_W, $src_H); //复制图像并改变大小
imagejpeg($tn, $small_img); //输出图像
}

方法二、

http://www.jb51.net/article/52380.htm

/** 

* desription 压缩图片 
* @param sting $imgsrc 图片路径 
* @param string $imgdst 压缩后保存路径 
*/
function image_png_size_add($imgsrc,$imgdst){ 
  list($width,$height,$type)=getimagesize($imgsrc); 
  $new_width = $width; 
  $new_height = $height; 
  echo "<br>imgdst=".$imgdst.",type=".$type."<br>";
  switch($type){ 
    case 1: 
      $giftype=check_gifcartoon($imgsrc); 
      if($giftype){ 
        header('Content-Type:image/gif'); 
        $image_wp=imagecreatetruecolor($new_width, $new_height); 
        $image = imagecreatefromgif($imgsrc); 
        imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); 
        imagejpeg($image_wp, $imgdst,75); 
        imagedestroy($image_wp); 
      } 
      break; 
    case 2: 
      header('Content-Type:image/jpeg'); 
      $image_wp=imagecreatetruecolor($new_width, $new_height); 
      $image = imagecreatefromjpeg($imgsrc); 
      imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); 
      imagejpeg($image_wp, $imgdst,75); 
      imagedestroy($image_wp); 
      break; 
    case 3: 
      header('Content-Type:image/png'); 
      $image_wp=imagecreatetruecolor($new_width, $new_height); 
      $image = imagecreatefrompng($imgsrc); 
      imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); 
      imagejpeg($image_wp, $imgdst,75); 
      imagedestroy($image_wp); 
      break; 
  } 
} 
/** 
* desription 判断是否gif动画 
* @param sting $image_file图片路径 
* @return boolean t 是 f 否 
*/
function check_gifcartoon($image_file){ 
  $fp = fopen($image_file,'rb'); 
  $image_head = fread($fp,1024); 
  fclose($fp); 
  return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'NETSCAPE2.0'."/",$image_head)?false:true; 
}