php生成高清縮略圖實例詳解

本文實例講述了php生成高清縮略圖的方法。分享給大家供大家參考，具體如下：

在使用php的函數生成縮略圖的使用，縮略圖很多情況下都會失真，這個時候需要有一些對應的解決方法。

1.用imagecreatetruecolor和imageCopyreSampled函數分別取代imagecreate和imagecopyresized

2.給imagejpeg的第三個參數帶上100(例:imagejpeg($ni,$toFile,100))

下面是具體的函數

function CreateSmallImage( $OldImagePath, $NewImagePath, $NewWidth=154, $NewHeight=134)
{
  // 取出原圖，獲得圖形信息getimagesize參數說明：0(寬),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);
  // 創建圖形,imagecreate參數說明：寬,高
  $NewImg = imagecreatetruecolor( $NewWidth, $NewHeight );
  //創建色彩,參數：圖形,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 ); //紅色
  $blue = ImageColorAllocate( $NewImg, 0, 0, 255 ); //藍色
  $other = ImageColorAllocate( $NewImg, 0, 255, 0 );
  //新圖形高寬處理
  $WriteNewWidth = $NewHeight*($OldImageInfo[0] / $OldImageInfo[1]); //要寫入的高度
  $WriteNewHeight = $NewWidth*($OldImageInfo[1] / $OldImageInfo[0]); //要寫入的寬度
  //這樣處理圖片比例會失調，但可以填滿背景
  if ($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為基礎,如果新寬小於或等於$NewWidth,則成立
  if ( $WriteNewWidth <= $NewWidth ) {
    $WriteNewWidth = $WriteNewWidth; //用判斷後的大小
    $WriteNewHeight = $NewHeight; //用規定的大小
    $WriteX = floor( ($NewWidth-$WriteNewWidth) / 2 ); //在新圖片上寫入的X位置計算
    $WriteY = 0;
  } else {
    $WriteNewWidth = $NewWidth; // 用規定的大小
    $WriteNewHeight = $WriteNewHeight; //用判斷後的大小
    $WriteX = 0;
    $WriteY = floor( ($NewHeight-$WriteNewHeight) / 2 ); //在新圖片上寫入的X位置計算
  }
  //舊圖形縮小後,寫入到新圖形上(復制),imagecopyresized參數說明：新舊, 新xy舊xy, 新寬高舊寬高
  @imageCopyreSampled( $NewImg, $OldImg, $WriteX, $WriteY, 0, 0, $WriteNewWidth, $WriteNewHeight, $OldImageInfo[0], $OldImageInfo[1] );
  //保存文件
//  @imagegif( $NewImg, $NewImagePath );
  @imagejpeg($NewImg, $NewImagePath, 100);
  //結束圖形
  @imagedestroy($NewImg);
}
CreateSmallImage("./images/jiexie.jpg","./images/jiexie.small.jpg",200,300);
CreateSmallImage("./images/jiexie.jpg","./images/jiexie.middle.jpg",400,500);

希望本文所述對大家php程序設計有所幫助。