php图片按比较生成缩略图片代码_PHP教程

图片按在比较进行放大缩小，这得利用php教程 gd库的函数现实现，我们会利用到imagecreatetruecolor(),imagecopyresampled()来操作

function my_image_resize($src_file, $dst_file, $dst_width=32, $dst_height=32) {
if($dst_width echo "params width or height error !";
exit();
}
if(!file_exists($src_file)) {
echo $src_file . " is not exists !";
exit();
}

$type=exif_imagetype($src_file);
$support_type=array(imagetype_jpeg , imagetype_png , imagetype_gif);

if(!in_array($type, $support_type,true)) {
echo "this type of image does not support! only support jpg , gif or png";
exit();
}

switch($type) {
case imagetype_jpeg :
$src_img=imagecreatefromjpeg($src_file);
break;
case imagetype_png :
$src_img=imagecreatefrompng($src_file);
break;
case imagetype_gif :
$src_img=imagecreatefromgif($src_file);
break;
default:
echo "load image error!";
exit();
}
$src_w=imagesx($src_img);
$src_h=imagesy($src_img);
$ratio_w=1.0 * $dst_width/$src_w;
$ratio_h=1.0 * $dst_height/$src_h;
if ($src_w $x = ($dst_width-$src_w)/2;
$y = ($dst_height-$src_h)/2;
$new_img=imagecreatetruecolor($dst_width,$dst_height);
imagecopy($new_img,$src_img,$x,$y,0,0,$dst_width,$dst_height);
switch($type) {
case imagetype_jpeg :
imagejpeg($new_img,$dst_file,100);
break;
case imagetype_png :
imagepng($new_img,$dst_file);
break;
case imagetype_gif :
imagegif($new_img,$dst_file);
break;
default:
break;
}
} else {
$dstwh = $dst_width/$dst_height;
$srcwh = $src_w/$src_h;
if ($ratio_w $zoom_w = $dst_width;
$zoom_h = $zoom_w*($src_h/$src_w);
} else {
$zoom_h = $dst_height;
$zoom_w = $zoom_h*($src_w/$src_h);
}

$zoom_img=imagecreatetruecolor($zoom_w, $zoom_h);
imagecopyresampled($zoom_img,$src_img,0,0,0,0,$zoom_w,$zoom_h,$src_w,$src_h);
$new_img=imagecreatetruecolor($dst_width,$dst_height);
$x = ($dst_width-$zoom_w)/2;
$y = ($dst_height-$zoom_h)/2+1;
imagecopy($new_img,$zoom_img,$x,$y,0,0,$dst_width,$dst_height);
switch($type) {
case imagetype_jpeg :
imagejpeg($new_img,$dst_file,100);
break;
case imagetype_png :
imagepng($new_img,$dst_file);
break;
case imagetype_gif :
imagegif($new_img,$dst_file);
break;
default:
break;
}
}
}

总结，我们要生成比例生成小图就利用$dstwh = $dst_width/$dst_height;
$srcwh = $src_w/$src_h;进行判断，然后再生成。