php如何使用GD创建保持宽高比缩略图

这篇文章主要介绍了php如何使用GD创建保持宽高比缩略图，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。

具体如下：

/*** Create a thumbnail image from $inputFileName no taller or wider than* $maxSize. Returns the new image resource or false on error.* Author: mthorn.net*/function thumbnail($inputFileName, $maxSize = 100){ $info = getimagesize($inputFileName);  $type = isset($info['type']) ? $info['type'] : $info[2];  // Check support of file type if ( !(imagetypes() & $type) ) {   // Server does not support file type   return false; }  $width = isset($info['width']) ? $info['width'] : $info[0]; $height = isset($info['height']) ? $info['height'] : $info[1];  // Calculate aspect ratio $wRatio = $maxSize / $width; $hRatio = $maxSize / $height;  // Using imagecreatefromstring will automatically detect the file type $sourceImage = imagecreatefromstring(file_get_contents($inputFileName));  // Calculate a proportional width and height no larger than the max size. if ( ($width <= $maxSize) && ($height <= $maxSize) ) {   // Input is smaller than thumbnail, do nothing   return $sourceImage; } elseif ( ($wRatio * $height) < $maxSize ) {   // Image is horizontal   $tHeight = ceil($wRatio * $height);   $tWidth = $maxSize; } else {   // Image is vertical   $tWidth = ceil($hRatio * $width);   $tHeight = $maxSize; }  $thumb = imagecreatetruecolor($tWidth, $tHeight);  if ( $sourceImage === false ) {   // Could not load image   return false; }  // Copy resampled makes a smooth thumbnail imagecopyresampled($thumb,$sourceImage,0,0,0,0,$tWidth,$tHeight,$width,$height); imagedestroy($sourceImage);  return $thumb;} /*** Save the image to a file. Type is determined from the extension.* $quality is only used for jpegs.* Author: mthorn.net*/function imageToFile($im, $fileName, $quality = 80){ if ( !$im || file_exists($fileName) ) {   return false; }  $ext = strtolower(substr($fileName, strrpos($fileName, '.')));  switch ( $ext ) {  case '.gif':  imagegif($im, $fileName);  break;  case '.jpg':  case '.jpeg':  imagejpeg($im, $fileName, $quality);  break;  case '.png':  imagepng($im, $fileName);  break;  case '.bmp':  imagewbmp($im, $fileName);  break;  default:  return false; }  return true;}$im = thumbnail('temp.jpg', 100);imageToFile($im, 'temp-thumbnail.jpg');

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