PHP生成同比例的缩略图实现程序_PHP教程

/**********************
*@filename - path to the image
*@tmpname - temporary path to thumbnail
*@xmax - max width
*@ymax - max height
*/
function resize_image($filename, $tmpname, $xmax, $ymax)
{
$ext = explode(".", $filename);
$ext = $ext[count($ext)-1];

if($ext == "jpg" || $ext == "jpeg")
$im = imagecreatefromjpeg($tmpname);
elseif($ext == "png")
$im = imagecreatefrompng($tmpname);
elseif($ext == "gif")
$im = imagecreatefromgif($tmpname);

$x = imagesx($im);
$y = imagesy($im);

if($x <= $xmax && $y <= $ymax)
return $im;

if($x >= $y) {
$newx = $xmax;
$newy = $newx * $y / $x;
}
else {
$newy = $ymax;
$newx = $x / $y * $newy;
}

$im2 = imagecreatetruecolor($newx, $newy);
imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y);
return $im2;
}

function creat_thumbnail($img,$w,$h,$path)
{
$org_info = getimagesize($img); //获得图像大小且是通过post传递过来的
//var_dump($org_info);
//Array ( [0] => 1024 [1] => 768 [2] => 3 [3] => width="1024" height="768" [bits] => 8 [mime] => image/png )
$orig_x = $org_info[0]; //图像宽度
$orig_y = $org_info[1]; //图像高度
$orig_type = $org_info[2]; //图片类别即后缀 1 = GIF，2 = JPG，3 = PNG，

//是真彩色图像
if (function_exists("imagecreatetruecolor"))
{
switch($orig_type)
{
//从给定的gif文件名中取得的图像
case 1 : $thumb_type = ".gif"; $_creatImage = "imagegif"; $_function = "imagecreatefromgif";
break;
//从给定的jpeg,jpg文件名中取得的图像
case 2 : $thumb_type = ".jpg"; $_creatImage = "imagejpeg"; $_function = "imagecreatefromjpeg";
break;
//从给定的png文件名中取得的图像
case 3 : $thumb_type = ".png"; $_creatImage = "imagepng"; $_function = "imagecreatefrompng";
break;
}
}
//如果从给定的文件名可取得的图像
if(function_exists($_function))
{
$orig_image = $_function($img); //从给定的$img文件名中取得的图像
}
if (($orig_x / $orig_y) >= (4 / 3)) //如果宽/高 >= 4/3
{
$y = round($orig_y / ($orig_x / $w)); //对浮点数进行四舍五入
$x = $w;
}
else //即 高/宽 >= 4/3
{
$x = round($orig_x / ($orig_y / $h));
$y = $h;
}
$sm_image = imagecreatetruecolor($x, $y); //创建真彩色图片
//重采样拷贝部分图像并调整大小
Imagecopyresampled($sm_image, $orig_image, 0, 0, 0, 0, $x, $y, $orig_x, $orig_y);
//imageJPEG($sm_image, '', 80); //在浏览器输出图像
$tnpath = $path."/"."s_".date('YmdHis').$thumb_type; //缩略图的路径
$thumbnail = @$_creatImage($sm_image, $tnpath, 80); //生成图片,成功返回true(或1)
imagedestroy ($sm_image); //销毁图像
if($thumbnail==true)
{
return $tnpath;
}
}