程序|源代码|缩略图
处理方法是:
1.当原图的宽或高任一比规定的尺寸小,只进行等比缩略处理,
2.当原图的宽与高都比规定尺寸大,先进行等比缩略处理,然后算出居中位置进行裁剪
以下是源代码：
$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);
}
}
?>