如何在php中生成高清缩略图

函数CreateSmallImage( $OldImagePath, $NewImagePath, $NewWidth=154, $NewHeight=134)
{
  // 取出原图，获取图形信息 getimagesize 参数说明：0(宽度)、1(高度)、2(1gif/2jpg/3png)、3(width="638" height="340")
  $OldImageInfo = getimagesize($OldImagePath);
  如果 ( $OldImageInfo[2] == 1 ) $OldImg = @imagecreatefromgif($OldImagePath);
  elseif ( $OldImageInfo[2] == 2 ) $OldImg = @imagecreatefromjpeg($OldImagePath);
  否则 $OldImg = @imagecreatefrompng($OldImagePath);
  //创建图形，imagecreate参数说明：width、height
  $NewImg = imagecreatetruecolor( $NewWidth, $NewHeight );
  //创建颜色，参数：图形，红色(0-255)，绿色(0-255)，蓝色(0-255)
  $black = ImageColorAllocate( $NewImg, 0, 0, 0 ); // 黑色的
  $white = ImageColorAllocate( $NewImg, 255, 255, 255 ); //白色的$red = ImageColorAllocate( $NewImg, 255, 0, 0 ); //红色的
  $blue = ImageColorAllocate( $NewImg, 0, 0, 255 ); // 蓝色的
  $其他 = ImageColorAllocate( $NewImg, 0, 255, 0 );
  //新建图形高宽处理
  $WriteNewWidth = $NewHeight*($OldImageInfo[0] / $OldImageInfo[1]); //要写入的高度
  $WriteNewHeight = $NewWidth*($OldImageInfo[1] / $OldImageInfo[0]); //要写入的宽度
  //这样处理的话图片比例会不平衡，但是可以填充背景
  if ($OldImageInfo[0] / $NewWidth > $org_info[1] / $NewHeight) {
    $WriteNewWidth = $NewWidth;
    $WriteNewHeight = $NewWidth / ($OldImageInfo[0] / $OldImageInfo[1]);
  } 别的 {
    $WriteNewWidth = $NewHeight * ($OldImageInfo[0] / $OldImageInfo[1]);
    $WriteNewHeight = $NewHeight;
  }
  //根据$NewHeight，如果新宽度小于等于$NewWidth则为true
  如果（ $WriteNewWidth <= $NewWidth ）{
    $WriteNewWidth = $WriteNewWidth; //使用确定的大小
    $WriteNewHeight = $NewHeight; //使用指定的大小
    $WriteX = 地板( ($NewWidth-$WriteNewWidth) / 2 ); // 计算新图片上写入的X位置
    $WriteY = 0;
  } 别的 {$WriteNewWidth = $NewWidth; // 使用指定的大小
    $WriteNewHeight = $WriteNewHeight; //使用确定的大小
    $WriteX = 0;
    $WriteY = 地板( ($NewHeight-$WriteNewHeight) / 2 ); //计算新图片上写的X位置
  }
  //旧图形缩小后，写入新图形（复制）​​，imagecopyresized参数说明：new和old、新xy和旧xy、新宽高、旧宽高
  @imageCopyreSampled( $NewImg, $OldImg, $WriteX, $WriteY, 0, 0, $WriteNewWidth, $WriteNewHeight, $OldImageInfo[0], $OldImageInfo[1] );
  //保存文档
// @imagegif( $NewImg, $NewImagePath );
  @imagejpeg($NewImg, $NewImagePath, 100);
  //结束图形
  @imagedestroy($NewImg);
}
CreateSmallImage("./images/jiexie.jpg","./images/jiexie.small.jpg",200,300);
CreateSmallImage("./images/jiexie.jpg","./images/jiexie.middle.jpg",400,500);