Introduction to the method of generating thumbnails in php

php method to generate thumbnails: first create a PHP sample file; then set the generated image format through "header("content-type:image/png");"; finally press the "image_resize" method Specify the size to generate thumbnails.

Recommended: "PHP Video Tutorial"

Three ways to generate image thumbnails in PHP:

1. Thumbnail the large image to the specified range of the thumbnail. There may be white space (the details of the original image will not be lost)

2. Shrink the large image to the specified range. Within the range specified by the thumbnail, no white space is left (the original image will be zoomed in the center, and the excess part is cropped)

3. Thumbnail the large image to the range specified by the thumbnail, without leaving any white space (the original image The right and bottom edges that are not in proportion will be cut off)

The following is the code:

<?php
// +----------------------------------------------------------------------
// |  把大图缩略到缩略图指定的范围内,可能有留白（原图细节不丢失）
// +---------------------------------------------------------------------- 
$w = $_GET[&#39;w&#39;]?$_GET[&#39;w&#39;]:200;
$h = $_GET[&#39;h&#39;]?$_GET[&#39;h&#39;]:200;
$filename = "stand_test_".$w."_".$h.".jpg";
image_resize( &#39;test.jpg&#39;,$filename, $w, $h);
header("content-type:image/png");//设定生成图片格式
echo file_get_contents($filename);
  
function image_resize($f, $t, $tw, $th){
// 按指定大小生成缩略图，而且不变形，缩略图函数
        $temp = array(1=>&#39;gif&#39;, 2=>&#39;jpeg&#39;, 3=>&#39;png&#39;);
  
        list($fw, $fh, $tmp) = getimagesize($f);
  
        if(!$temp[$tmp]){
                return false;
        }
        $tmp = $temp[$tmp];
        $infunc = "imagecreatefrom$tmp";
        $outfunc = "image$tmp";
  
        $fimg = $infunc($f);
  
        // 使缩略后的图片不变形，并且限制在 缩略图宽高范围内
        if($fw/$tw > $fh/$th){
            $th = $tw*($fh/$fw);
        }else{
            $tw = $th*($fw/$fh);
        }
  
        $timg = imagecreatetruecolor($tw, $th);
        imagecopyresampled($timg, $fimg, 0,0, 0,0, $tw,$th, $fw,$fh);
        if($outfunc($timg, $t)){
                return true;
        }else{
                return false;
        }
}
?>

<?php
// +----------------------------------------------------------------------
// |  把大图缩略到缩略图指定的范围内，不留白（原图会居中缩放，把超出的部分裁剪掉）
// +----------------------------------------------------------------------
$w = $_GET[&#39;w&#39;]?$_GET[&#39;w&#39;]:200;
$h = $_GET[&#39;h&#39;]?$_GET[&#39;h&#39;]:200;
$filename = "cut_test_".$w."_".$h.".jpg";
image_resize( &#39;test.jpg&#39;,$filename, $w, $h);
header("content-type:image/png");//设定生成图片格式
echo file_get_contents($filename);
  
// 按指定大小生成缩略图，而且不变形，缩略图函数
function image_resize($f, $t, $tw, $th){
        $temp = array(1=>&#39;gif&#39;, 2=>&#39;jpeg&#39;, 3=>&#39;png&#39;);
        list($fw, $fh, $tmp) = getimagesize($f);
        if(!$temp[$tmp]){
                return false;
        }
        $tmp = $temp[$tmp];
        $infunc = "imagecreatefrom$tmp";
        $outfunc = "image$tmp";
  
        $fimg = $infunc($f);
//      $fw = 10;
//      $fh = 4;
//      $tw = 4;
//      $th = 2;
        // 把图片铺满要缩放的区域
        if($fw/$tw > $fh/$th){
            $zh = $th;
            $zw = $zh*($fw/$fh);
            $_zw = ($zw-$tw)/2;
        }else{
            $zw = $tw;
            $zh = $zw*($fh/$fw);
            $_zh = ($zh-$th)/2;
        }
//        echo $zw."<br>";   
//        echo $zh."<br>";   
//        echo $_zw."<br>";   
//        echo $_zh."<br>";   
//        exit;
        $zimg = imagecreatetruecolor($zw, $zh);
        // 先把图像放满区域
        imagecopyresampled($zimg, $fimg, 0,0, 0,0, $zw,$zh, $fw,$fh);
  
        // 再截取到指定的宽高度
        $timg = imagecreatetruecolor($tw, $th);
        imagecopyresampled($timg, $zimg, 0,0, 0+$_zw,0+$_zh, $tw,$th, $zw-$_zw*2,$zh-$_zh*2);
//        
        if($outfunc($timg, $t)){
                return true;
        }else{
                return false;
        }
}
  
?>

<?php
// +----------------------------------------------------------------------
// | 把大图缩略到缩略图指定的范围内，不留白（原图会剪切掉不符合比例的右边和下边）
// +----------------------------------------------------------------------
$w = $_GET[&#39;w&#39;]?$_GET[&#39;w&#39;]:200;
$h = $_GET[&#39;h&#39;]?$_GET[&#39;h&#39;]:200;
$filename = "strict_test_".$w."_".$h.".jpg";
image_resize( &#39;test.jpg&#39;,$filename, $w, $h);
header("content-type:image/png");//设定生成图片格式
echo file_get_contents($filename);
  
function image_resize($f, $t, $tw, $th){
// 按指定大小生成缩略图，而且不变形，缩略图函数
        $temp = array(1=>&#39;gif&#39;, 2=>&#39;jpeg&#39;, 3=>&#39;png&#39;);
  
        list($fw, $fh, $tmp) = getimagesize($f);
  
        if(!$temp[$tmp]){
                return false;
        }
        $tmp = $temp[$tmp];
        $infunc = "imagecreatefrom$tmp";
        $outfunc = "image$tmp";
  
        $fimg = $infunc($f);
  
        if($fw/$tw > $fh/$th){
                $fw = $tw * ($fh/$th);
        }else{
                $fh = $th * ($fw/$tw);
        }
  
        $timg = imagecreatetruecolor($tw, $th);
        imagecopyresampled($timg, $fimg, 0,0, 0,0, $tw,$th, $fw,$fh);
        if($outfunc($timg, $t)){
                return true;
        }else{
                return false;
        }
}
?>

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