php缩略图代码，imagecopyresampled函数生成缩略图

function CreateImage($SrcImageUrl, $DirImageUrl, $Width, $Height)
{
$img;
$srcw;
$new_width;
$srch;
$new_height;
// 图片类型
$type = substr(strrchr($SrcImageUrl, "."), 1);
// 初始化图像
if($type == "jpg")
$img = imagecreatefromjpeg($SrcImageUrl);
if($type == "gif")
$img = imagecreatefromgif($SrcImageUrl);
if($type == "png")
$img = imagecreatefrompng($SrcImageUrl);
$srcw = imagesx($img);
$srch = imagesy($img);
if ($srcw / $srch > $Width / $Height)
{
if ($srcw > $Width)
{
$new_width = $Width;
$new_height = $srch * ($Width / $srcw);
}
else
{
$new_width = $srcw;
$new_height = $srch;
}
}
else
{
if ($srch > $Height)
{
$new_height = $Height;
$new_width = $srcw * ($Height / $srch);
}
else
{
$new_width = $srcw;
$new_height = $srch;
}
}
$new_image = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($new_image, $img, 0, 0, 0, 0, $new_width, $new_height, $srcw, $srch);
imagejpeg($new_image, $DirImageUrl);
imagedestroy($img);
imagedestroy($new_image);
}

3、改进后代码：

/*
*$o_photo 原图路径
*$d_photo 处理后图片路径
*$width    定义宽
*$height   定义高
*调用方法   cutphoto("test.jpg","temp.jpg",256,146);
*/
function cutphoto($o_photo,$d_photo,$width,$height){
$temp_img = imagecreatefromjpeg($o_photo);
$o_width   = imagesx($temp_img);      //取得原图宽
$o_height = imagesy($temp_img);      //取得原图高
//判断处理方法
if($width>$o_width || $height>$o_height){//原图宽或高比规定的尺寸小,进行压缩
$newwidth=$o_width;
$newheight=$o_height;
if($o_width>$width){
$newwidth=$width;
$newheight=$o_height*$width/$o_width;
}
if($newheight>$height){
$newwidth=$newwidth*$height/$newheight;
$newheight=$height;
}
//缩略图片
$new_img = imagecreatetruecolor($newwidth, $newheight);
imagecopyresampled($new_img, $temp_img, 0, 0, 0, 0, $newwidth, $newheight, $o_width, $o_height);
imagejpeg($new_img , $d_photo);
imagedestroy($new_img);
}else{//原图宽与高都比规定尺寸大,进行压缩后裁剪
if($o_height*$width/$o_width>$height){//先确定width与规定相同,如果height比规定大,则ok
$newwidth=$width;
$newheight=$o_height*$width/$o_width;
$x=0;
$y=($newheight-$height)/2;
}else{ //否则确定height与规定相同,width自适应
$newwidth=$o_width*$height/$o_height;
$newheight=$height;
$x=($newwidth-$width)/2;
$y=0;
}
//缩略图片
$new_img = imagecreatetruecolor($newwidth, $newheight);
imagecopyresampled($new_img, $temp_img, 0, 0, 0, 0, $newwidth, $newheight, $o_width, $o_height);
imagejpeg($new_img , $d_photo);
imagedestroy($new_img);
$temp_img = imagecreatefromjpeg($d_photo);
$o_width   = imagesx($temp_img);      //取得缩略图宽
$o_height = imagesy($temp_img);      //取得缩略图高
//裁剪图片
$new_imgx = imagecreatetruecolor($width,$height);
imagecopyresampled($new_imgx,$temp_img,0,0,$x,$y,$width,$height,$width,$height);
imagejpeg($new_imgx , $d_photo);
imagedestroy($new_imgx);
}
}
?>