常常在處理一些使用者上傳的圖片時
會需要讓系統自動產生圖檔的縮圖(例如無名的相簿預覽等等的功能)PHP程式在處理圖片縮圖的方式
較常見的有兩種: GD ，以及ImageMagick
GD是php內建的圖形函式庫，一般只要安裝php都會有內建此功能
而ImageMagick則是要另外安裝，再用下面的方法呼叫:
// 呼叫 ImageMagic 的 convert exec(“convert -geometry 200×200 big_img.jpg small_img.jpg“);
其它的參數
1.生成縮圖
a.指定大小 # convert -sample 80×40 input.jpg output.jpg
b.利用比例 # convert -sample 25%x25% input.jpg output.jpg
2.旋轉圖形
利用cotate參數，+90表順時針旋轉90度，而-90則表逆時針轉90度
# convert -rotate 90 input.jpg output.jpg
3.轉換格式
以附檔名為準，如下例就是將jpg轉換成png的用法
# convert input.jpg output.png
4.一次使用多種命令
# convert -sample 25%x25% -spread 4 \ -charcoal 4 input.jpg output.jpg
詳細使用方法請參照:
http://www.imagemagick.org/script/index.php
GD圖形函式庫除的詳細功能可參照:
http://www.php5.idv.tw/modules.php?mod=books&act=index&cid=29
下面為一個用GD函式庫所寫成的縮圖函式。
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class resize_img { var $image_path = ''; //holds the image path var $sizelimit_x = 250; //the limit of the image width var $sizelimit_y = 250; //the limit of the image height var $image_resource = ''; //holds the image resource var $keep_proportions = true; //if true it keeps the image proportions when resized var $resized_resource = ''; //holds the resized image resource var $hasGD = false; var $output = 'SAME'; //can be JPG, GIF, PNG, or SAME (same will save as old type) function resize_img() { if( function_exists('gd_info') ){ $this->hasGD = true; } } function resize_image( $image_path ) { if( $this->hasGD === false ){ return false; } //no GD installed on the server! list($img_width, $img_height, $img_type, $img_attr) = @getimagesize( $image_path ); //this is going to get the image width, height, and format if( ( $img_width != 0 ) || ( $img_width != 0 ) ) //make sure it was loaded correctly { switch( $img_type ) { case 1: //GIF $this->image_resource = @imagecreatefromgif( $image_path ); if( $this->output == 'SAME' ){ $this->output = 'GIF'; } break; case 2: //JPG $this->image_resource = @imagecreatefromjpeg( $image_path ); if( $this->output == 'SAME' ){ $this->output = 'JPG'; } break; case 3: //PNG $this->image_resource = @imagecreatefrompng( $image_path ); if( $this->output == 'SAME' ){ $this->output = 'PNG'; } } if( $this->image_resource === '' ){ return false; } //it wasn't able to load the image } else{ return false; } //something happened! if( $this->keep_proportions === true ) { if( ($img_width-$this->sizelimit_x) > ($img_height-$this->sizelimit_y) ) { //if the width of the img is greater than the size limit we scale by width $scalex = ( $this->sizelimit_x / $img_width ); $scaley = $scalex; } else //if the height of the img is greater than the size limit we scale by height { $scalex = ( $this->sizelimit_y / $img_height ); $scaley = $scalex; } } else { $scalex = ( $this->sizelimit_x / $img_width ); $scaley = ( $this->sizelimit_y / $img_height ); //just make the image fit the image size limit if( $scalex > 1 ){ $scalex = 1; } if( $scaley > 1 ){ $scaley = 1; } //don't make it so it streches the image } $new_width = $img_width * $scalex; $new_height = $img_height * $scaley; $this->resized_resource = @imagecreatetruecolor( $new_width, $new_height ); //creates an image resource, //with the width and height of the size limits (or new resized proportion ) if( function_exists( 'imageantialias' )){ @imageantialias( $this->resized_resource, true ); } //helps in the quality of the image being resized @imagecopyresampled( $this->resized_resource, $this->image_resource, 0, 0, 0, 0, $new_width, $new_height, $img_width, $img_height ); //resize the iamge onto the resized resource @imagedestroy( $this->image_resource ); //destory old image resource return true; } function save_resizedimage( $path, $name ) { switch( strtoupper($this->output) ) { case 'GIF': //GIF @imagegif( $this->resized_resource, $path . $name . '.gif' ); break; case 'JPG': //JPG @imagejpeg( $this->resized_resource, $path . $name . '.jpg' ); break; case 'PNG': //PNG @imagepng( $this->resized_resource, $path . $name . '.png' ); } } function output_resizedimage() { $the_time = time(); header('Last-Modified: ' . date( 'D, d M Y H:i:s', $the_time ) . ' GMT'); header('Cache-Control: public'); switch( strtoupper($this->output) ) { case 'GIF': //GIF header('Content-type: image/gif'); @imagegif( $this->resized_resource ); break; case 'JPG': //JPG header('Content-type: image/jpg'); @imagejpeg( $this->resized_resource ); break; case 'PNG': //PNG header('Content-type: image/png'); @imagepng( $this->resized_resource ); } } function destroy_resizedimage() { @imagedestroy( $this->resized_resource ); @imagedestroy( $this->image_resource ); } } |
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//how to use the class: //makes a simple thumbnail of an image of 100x100 //and saves the image then outputs it. $imgresize = new resize_img(); $imgresize->sizelimit_x = 100; $imgresize->sizelimit_y = 100; $imgresize->keep_proportions = true; $imgresize->output = 'PNG'; if( $imgresize->resize_image('C:/treeshadows_001.gif' ) === false ) { echo 'ERROR!'; } else { $imgresize->save_resizedimage( 'C:/xampp/', 'treeshadows_001' ); $imgresize->output_resizedimage(); } $imgresize->destroy_resizedimage(); |