PHP crop any image to a fixed size_PHP tutorial

做一个首页调用图像，有时候往往需要获得固定大小的图像，因为首页的图像位置通常由设计人员指定好了，如果是做最新发布图像调用，因为不知道客户会上传什么比例的图像，所以，有时候也就没有办法确定图像的比例，前台页面编写人员通常会采用固定 img 元素高宽的办法来达到控制图像不溢出，但如果图像的比例不是需要的比例，就会造成图像调用后变形，很大程度上影响了页面的美观，有解决的方法是，按照原图比例进行缩放，缩放后的图像难免会有空白，空白处填以颜色，这样虽然图像不变形了，但这样会有很多问题，比如，如果用户发一个图像很高但宽度一般的图像，如果压缩成一个1：1的图像，那么压缩后基本就会看不到图像了。
我这里的解决办法是，任意图像裁剪成固定大小，图像不变形，空白处拉伸填充，图像始终铺满，不留空白，用过bcastr的朋友应该知道，bcastr就是保证了图像调用的不变形，对一个固定大小输出的图像框，源图有以下几种情况：
1：需要输出的图像的高宽比源图的高宽都小，写成判断 $new_width<$src_width && $new_height<$src_width
2：需要输出的图像的高宽比原图的高宽都大，写成判断 $new_width>$src_width && $new_height>$src_width
3：排除第1，2两种，即一边放大，一边缩小的情况加上等于的判断
对于1，2，函数处理代码完全相同，所以可以归纳成一个处理语句

给出php实现代码

/*
* Description: The function is to crop an image into an image of any size without deforming the image
* Parameter description: Enter the file name of the image to be processed, and generate Save the file name of the new picture, generate the width of the new picture, and generate the height of the new picture
* written by smallchicken
* time 2008-12-18
*/
// Get any size image, Stretch the missing areas without deformation or leaving any blank spaces
function my_image_resize($src_file, $dst_file, $new_width, $new_height) {
if($new_width <1 || $new_height <1) {
echo "params width or height error !";
exit();
}
if(!file_exists($src_file)) {
echo $src_file . " is not exists ! ";
exit();
}
// Image type
$type=exif_imagetype($src_file);
$support_type=array(IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF);
if(!in_array($type, $support_type,true)) {
echo "this type of image does not support! only support jpg , gif or png";
exit();
}
//Load image
switch($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();
}
$w=imagesx($src_img);
$h=imagesy($src_img);
$ratio_w=1.0 * $new_width / $w;
$ratio_h=1.0 * $new_height / $h;
$ratio=1.0;
// The height and width of the generated image are smaller or larger than the original ones. The principle is to enlarge by a larger ratio. Scale down (the reduction ratio is smaller)
if( ($ratio_w < 1 && $ratio_h < 1) || ($ratio_w > 1 && $ratio_h > 1)) {
if ($ratio_w < $ratio_h) {
$ratio = $ratio_h ; // Case 1, the width ratio is smaller than the height direction, crop or enlarge according to the height ratio standard
}else {
$ratio = $ratio_w ;
}
// Define an intermediate temporary image whose aspect ratio just meets the target requirements
$inter_w=(int)($new_width / $ratio);
$inter_h=(int) ($new_height / $ratio);
$inter_img=imagecreatetruecolor($inter_w , $inter_h);
imagecopy($inter_img, $src_img, 0,0,0,0, $inter_w,$inter_h);
// Generate a temporary image with the maximum side length as the target image $ratio ratio
// Define a new image
$new_img=imagecreatetruecolor($new_width ,$new_height);
imagecopyresampled($new_img,$inter_img,0,0,0,0,$new_width,$new_height,$inter_w,$inter_h);
switch($type) {
case IMAGETYPE_JPEG :
imagejpeg($new_img, $dst_file,100); // Store image
break;
case IMAGETYPE_PNG :
imagepng($new_img,$dst_file,100);
break;
case IMAGETYPE_GIF :
imagegif($new_img,$dst_file,100);
break;
default:
break;
}
} // end if 1
// 2 One side of the target image is larger than the original image, and one side is smaller than the original image. First enlarge the ordinary image, and then crop it
// =if( ($ratio_w < 1 && $ratio_h > 1) || ($ratio_w >1 && $ratio_h <1) )
else{
$ratio=$ratio_h>$ratio_w? $ratio_h : $ratio_w; //Take the value with the larger ratio
// Define a large intermediate image whose height or width is equal to the target image, and then enlarge the original image
$inter_w=(int)($w * $ratio);
$inter_h=(int) ( $h * $ratio);
$inter_img=imagecreatetruecolor($inter_w , $inter_h);
//Crop the original image after scaling
imagecopyresampled($inter_img,$src_img,0,0,0 ,0,$inter_w,$inter_h,$w,$h);
//Define a new image
$new_img=imagecreatetruecolor($new_width,$new_height);
imagecopy($new_img, $ inter_img, 0,0,0,0,$new_width,$new_height);
switch($type) {
case IMAGETYPE_JPEG :
imagejpeg($new_img, $dst_file,100); // Store image
break;
case IMAGETYPE_PNG :
imagepng($new_img,$dst_file,100);
break;
case IMAGETYPE_GIF :
imagegif($new_img,$dst_file,100);
break;
default:
break;
}
}// if3
}// end function
?>