PHP实现压缩图片尺寸并转为jpg格式的方法示例

<?php
function imagetojpg($srcfile,$dstfile,$towidth,$toheight)
{
  $quality=80;
  $data = @getimagesize($srcfile);
  switch ($data['2'])
  {
  case 1:
    $im = imagecreatefromgif($srcfile);
    break;
  case 2:
    $im = imagecreatefromjpeg($srcfile);
    break;
  case 3:
    $im = imagecreatefrompng($srcfile);
    break;
  case 6:
  $im = imagecreatefrombmp( $srcfile );
  break;
  }
  // $dstx=$srcw=@imagesx($im);
  // $dsty=$srch=@imagesy($im);
  $srcw=@imagesx($im);
  $srch=@imagesy($im);
  //$towidth,$toheight
  if($toheight/$srcw > $towidth/$srch){
    $b = $toheight/$srch;
  }else{
    $b = $towidth/$srcw;
  }
  //计算出图片缩放后的宽高
  // floor 舍去小数点部分，取整
  $new_w = floor($srcw*$b);
  $new_h = floor($srch*$b);
  $dstx=$new_w;
  $dsty=$new_h;
  $ni=@imagecreatetruecolor($dstx,$dsty);
  @imagecopyresampled($ni,$im,0,0,0,0,$dstx,$dsty,$srcw,$srch);
  @imagejpeg($ni,$dstfile,$quality);
  @imagedestroy($im);
  @imagedestroy($ni);
}
//imagetojpg('源文件名','目标文件名',目标宽,目标高);
imagetojpg('test2.png','test2.jpg',80,50);