php等比例生成缩略图

function reSizeImg($imgSrc, $resize_width, $resize_height, $isCut=false) {

	//图片的类型

	$type = substr ( strrchr ( $imgSrc, "." ), 1 );

	//初始化图象

	if ($type == "jpg") {

		$im = imagecreatefromjpeg ( $imgSrc );

	}

	if ($type == "gif") {

		$im = imagecreatefromgif ( $imgSrc );

	}

	if ($type == "png") {

		$im = imagecreatefrompng ( $imgSrc );

	}

	//目标图象地址

	$full_length = strlen ( $imgSrc );

	$type_length = strlen ( $type );

	$name_length = $full_length - $type_length;

	$name = substr ( $imgSrc, 0, $name_length - 1 );

	$dstimg = $name . "_s." . $type;



	$width = imagesx ( $im );

	$height = imagesy ( $im );



	//生成图象

	//改变后的图象的比例

	$resize_ratio = ($resize_width) / ($resize_height);

	//实际图象的比例

	$ratio = ($width) / ($height);

	if (($isCut) == 1) //裁图

		{

		if ($ratio >= $resize_ratio) //高度优先

		{

			$newimg = imagecreatetruecolor ( $resize_width, $resize_height );

			imagecopyresampled ( $newimg, $im, 0, 0, 0, 0, $resize_width, $resize_height, (($height) * $resize_ratio), $height );

			ImageJpeg ( $newimg, $dstimg );

		}

		if ($ratio < $resize_ratio) //宽度优先

		{

			$newimg = imagecreatetruecolor ( $resize_width, $resize_height );

			imagecopyresampled ( $newimg, $im, 0, 0, 0, 0, $resize_width, $resize_height, $width, (($width) / $resize_ratio) );

			ImageJpeg ( $newimg, $dstimg );

		}

	} else //不裁图

	{

		if ($ratio >= $resize_ratio) {

			$newimg = imagecreatetruecolor ( $resize_width, ($resize_width) / $ratio );

			imagecopyresampled ( $newimg, $im, 0, 0, 0, 0, $resize_width, ($resize_width) / $ratio, $width, $height );

			ImageJpeg ( $newimg, $dstimg );

		}

		if ($ratio < $resize_ratio) {

			$newimg = imagecreatetruecolor ( ($resize_height) * $ratio, $resize_height );

			imagecopyresampled ( $newimg, $im, 0, 0, 0, 0, ($resize_height) * $ratio, $resize_height, $width, $height );

			ImageJpeg ( $newimg, $dstimg );

		}

	}

	ImageDestroy ( $im );

}