PHP压缩图片

function scale_dimensions_within_limits($w,$h,$max_w,$max_h){
  // $w is the width of the current rectangle
  // $h is the height of the current rectangle
  // $max_w is the maximum width that an image can be sized
  // $max_h is the maximum height that an image can be sized

  // **** Here's where the magic is starts ****
  // Switch the concept of horiz/vertical/square to long/short side
  $short_side_len = ($w   $long_side_len = ($w > $h ? $w : $h);
  // Set a variable to the variable name of the output variable
  $ssvar = ($w > $h ? 'h':'w');
  $lsvar = ($w > $h ? 'w':'h');
  $maxLSvar = "max_".$lsvar;
  $maxSSvar = "max_".$ssvar;

  // Do the first pass on the long side
  $ratio = $$maxLSvar/$long_side_len;
  $newSS = round($short_side_len * $ratio);
  $newLS = round($long_side_len * $ratio);

  // *** Note - the only coditional block!
  // If short side is still out of limit, limit the short side and adjust
  if($newSS > $$maxSSvar){
    $ratio = $$maxSSvar/$newSS;
    $newLS = round($ratio*$newLS);
    $newSS = $$maxSSvar;
  }

  // **** Here's where the magic ends ****
  // Re-couple the h/w (or w/h) with the long/shortside counterparts
  // $$ means it's a variable variable (dynamic assignment)
  $$ssvar = $newSS;
  $$lsvar = $newLS;

  // Prep the return array
  $dimensions['w'] = $w; // this is derived from either $ssvar or $lsvar
  $dimensions['h'] = $h; return $dimensions;
}

PHP