PHP crops the image without affecting its shape

This time I will bring you PHP cropping without affecting the shape of the image. What are the precautions for PHP cropping without affecting the shape of the image? The following is a practical case. Let’s take a look. . Functional requirements:

Automatically crop the image after uploading it, and then display the cropped image in the front desk.

<?
 *exif_imagetype -- 判断一个图像的类型
 *说明：函数功能是把一个图像裁剪为任意大小的图像，图像不变形
 * 参数说明：输入 需要处理图片的 文件名，生成新图片的保存文件名，生成新图片的宽，生成新图片的高
 */
  // 获得任意大小图像，不足地方拉伸，不产生变形，不留下空白
 function my_image_resize($src_file, $dst_file , $new_width , $new_height) {
$new_width= intval($new_width);
$new_height=intval($new_width);
 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();
 }
 // 图像类型
 $type=exif_imagetype($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;
 $ratio=1.0;
 // 生成的图像的高宽比原来的都小，或都大 ，原则是 取大比例放大，取大比例缩小（缩小的比例就比较小了）
 if( ($ratio_w < 1 && $ratio_h < 1) || ($ratio_w > 1 && $ratio_h > 1)) {
 if($ratio_w < $ratio_h) {
 $ratio = $ratio_h ; // 情况一，宽度的比例比高度方向的小，按照高度的比例标准来裁剪或放大
 }else {
 $ratio = $ratio_w ;
 }
 // 定义一个中间的临时图像，该图像的宽高比 正好满足目标要求
 $inter_w=(int)($new_width / $ratio);
 $inter_h=(int) ($new_height / $ratio);
 $inter_img=imagecreatetruecolor($inter_w , $inter_h);
 //var_dump($inter_img);
 imagecopy($inter_img, $src_img, 0,0,0,0,$inter_w,$inter_h);
 // 生成一个以最大边长度为大小的是目标图像$ratio比例的临时图像
 // 定义一个新的图像
 $new_img=imagecreatetruecolor($new_width,$new_height);
 //var_dump($new_img);exit();
 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, $dst_file,100); // 存储图像
 break;
 case IMAGETYPE_PNG :
 imagepng($new_img,$dst_file,100);
 break;
 case IMAGETYPE_GIF :
 imagegif($new_img,$dst_file,100);
 break;
 default:
 break;
 }
 } // end if 1
 // 2 目标图像 的一个边大于原图，一个边小于原图 ，先放大平普图像，然后裁剪
 // =if( ($ratio_w < 1 && $ratio_h > 1) || ($ratio_w >1 && $ratio_h <1) )
 else{
 $ratio=$ratio_h>$ratio_w? $ratio_h : $ratio_w; //取比例大的那个值
 // 定义一个中间的大图像，该图像的高或宽和目标图像相等，然后对原图放大
 $inter_w=(int)($w * $ratio);
 $inter_h=(int) ($h * $ratio);
 $inter_img=imagecreatetruecolor($inter_w , $inter_h);
 //将原图缩放比例后裁剪
 imagecopyresampled($inter_img,$src_img,0,0,0,0,$inter_w,$inter_h,$w,$h);
 // 定义一个新的图像
 $new_img=imagecreatetruecolor($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, $dst_file,100); // 存储图像
 break;
 case IMAGETYPE_PNG :
 imagepng($new_img,$dst_file,100);
 break;
 case IMAGETYPE_GIF :
 imagegif($new_img,$dst_file,100);
 break;
 default:
 break;
 }
 }// if3
 }// end function
my_image_resize(&#39;test.gif&#39;,&#39;11111.gif&#39;,&#39;100px&#39;,&#39;100px&#39;);
?>

Editor’s summary:

The PHP image cropping function implemented above flexibly applies the relevant functions of the PHP gd library, including the usage of imagecreatefromjpeg, imagecreatefrompng, imagecreatefromgif, imagecreatetruecolor and other functions.

Therefore, flexibly mastering the usage of each function in the php gd library is crucial for the realization of functions such as cropping pictures, watermarks,
thumbnails
, etc.

Extended reading:

Example of generating thumbnails using php GD library Basic knowledge of php gd library Detailed explanation of the usage of GD function in PHP GD library php GD library generates high-quality thumbnails (example) PHP GD library function collection (collection) PHP uses gd library to implement screenshot example code Detailed explanation of the steps to add GD library support to PHP Sharing the steps to install GD library in php5 The whole process of installing php gd library with yum under linux How to open PHP GD library under windows php opens the GD library (windows environment) Example code for dynamically generating a line chart using the PHP GD library Example code for drawing 24-hour histogram using php GD library phpVerification code (GD library generates verification code) example php GD library code to upload images and create thumbnails Example of php GD library generating verification code I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

Recommended reading:

Detailed explanation of deleting newline characters when PHP reads files line by line

php gd library implementation service End image cropping and thumbnail preview function

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