php生成高清缩略图实例详解

本文实例讲述了php生成高清缩略图的方法。分享给大家供大家参考，具体如下：

在使用php的函数生成缩略图的使用，缩略图很多情况下都会失真，这个时候需要有一些对应的解决方法。

1.用imagecreatetruecolor和imageCopyreSampled函数分别取代imagecreate和imagecopyresized

2.给imagejpeg的第三个参数带上100(例:imagejpeg($ni,$toFile,100))

下面是具体的函数

    function CreateSmallImage( $OldImagePath, $NewImagePath, $NewWidth=154, $NewHeight=134)
    {
      // 取出原图，获得图形信息getimagesize参数说明：0(宽),1(高),2(1gif/2jpg/3png),3(width="638" height="340")
      $OldImageInfo = getimagesize($OldImagePath);
      if ( $OldImageInfo[2] == 1 ) $OldImg = @imagecreatefromgif($OldImagePath);
      elseif ( $OldImageInfo[2] == 2 ) $OldImg = @imagecreatefromjpeg($OldImagePath);
      else $OldImg = @imagecreatefrompng($OldImagePath);
      // 创建图形,imagecreate参数说明：宽,高
      $NewImg = imagecreatetruecolor( $NewWidth, $NewHeight );
      //创建色彩,参数：图形,red(0-255),green(0-255),blue(0-255)
      $black = ImageColorAllocate( $NewImg, 0, 0, 0 ); //黑色
      $white = ImageColorAllocate( $NewImg, 255, 255, 255 ); //白色
      $red  = ImageColorAllocate( $NewImg, 255, 0, 0 ); //红色
      $blue = ImageColorAllocate( $NewImg, 0, 0, 255 ); //蓝色
      $other = ImageColorAllocate( $NewImg, 0, 255, 0 );
      //新图形高宽处理
      $WriteNewWidth = $NewHeight*($OldImageInfo[0] / $OldImageInfo[1]); //要写入的高度
      $WriteNewHeight = $NewWidth*($OldImageInfo[1] / $OldImageInfo[0]); //要写入的宽度
      //这样处理图片比例会失调，但可以填满背景
      if ($OldImageInfo[0] / $NewWidth > $org_info[1] / $NewHeight) {
        $WriteNewWidth = $NewWidth;
        $WriteNewHeight = $NewWidth / ($OldImageInfo[0] / $OldImageInfo[1]);
      } else {
        $WriteNewWidth = $NewHeight * ($OldImageInfo[0] / $OldImageInfo[1]);
        $WriteNewHeight = $NewHeight;
      }
      //以$NewHeight为基础,如果新宽小于或等于$NewWidth,则成立
      if ( $WriteNewWidth <= $NewWidth ) {
        $WriteNewWidth = $WriteNewWidth; //用判断后的大小
        $WriteNewHeight = $NewHeight; //用规定的大小
        $WriteX = floor( ($NewWidth-$WriteNewWidth) / 2 ); //在新图片上写入的X位置计算
        $WriteY = 0;
      } else {
        $WriteNewWidth = $NewWidth; // 用规定的大小
        $WriteNewHeight = $WriteNewHeight; //用判断后的大小
        $WriteX = 0;
        $WriteY = floor( ($NewHeight-$WriteNewHeight) / 2 ); //在新图片上写入的X位置计算
      }
      //旧图形缩小后,写入到新图形上(复制),imagecopyresized参数说明：新旧, 新xy旧xy, 新宽高旧宽高
      @imageCopyreSampled( $NewImg, $OldImg, $WriteX, $WriteY, 0, 0, $WriteNewWidth, $WriteNewHeight, $OldImageInfo[0], $OldImageInfo[1] );
      //保存文件
    //  @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);

希望本文所述对大家php程序设计有所帮助。