Example of how to compress image size and convert to jpg format using PHP

This article mainly introduces the method of PHP to compress image size and convert it to jpg format, involving PHP's related operating skills for image reading, calculation, conversion, output, etc. Friends who need it can refer to it

The example in this article describes how PHP compresses image size and converts it to jpg format. Share it with everyone for your reference, the details are as follows:

<?php
function ImageToJPG($srcFile,$dstFile,$towidth,$toheight)
{
  $quality=80;
  $data = @GetImageSize($srcFile);
  switch ($data[&#39;2&#39;])
  {
  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(&#39;源文件名&#39;,&#39;目标文件名&#39;,目标宽,目标高);
ImageToJPG(&#39;test2.png&#39;,&#39;test2.jpg&#39;,80,50);

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