PHP缩略图
经常的时候我们会需要用到访问图片，这些需求一般是存在于用户上传图片之后，需要列表出所有他上传的图片。
这时候传回所有的原始大小图片固然没有问题，但是在网络比较差的情况下还是建议来读读本文件吧。
我们知道很多情况上传的档案就只是存在Server的本地的，这种情况下转换缩略图就有很多办法，比如可以使用命令调用本地的图片浏览工具的API，或者其他网络上提供的方法，这些方法要么就是支持的图片格式非常有限，要么就是header有问题等等。
并且但是现在我们的图片或者附件数据是存在数据库中的。由一个固定字符串字段存下来的。
我在网上找到一个很好使用的PHP缩图第三方类： imageclass.php
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<?php 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 ); }
}
?> |
这一个类支持的格式几乎涵盖了网络上主流的所有格式，GIF、PNG、JPG
调用这个类的方法是：
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<?php include("conn.php"); include("imageclass.php");
$result = odbc_exec($conn,"select * from ImageTable where id = ".htmlspecialchars($_REQUEST["id"]));
while (odbc_fetch_row($result)) { $Upload_File=odbc_result($result,"Upload_File"); $File_Ext = odbc_result($result,"File_Ext"); }
if($_REQUEST["min"]==null) { $File_Ext=strtolower($File_Ext); switch ($File_Ext) { case ".pdf": $ctype="application/pdf"; break; case ".exe": $ctype="application/octet-stream"; break; case ".zip": $ctype="application/zip"; break; case ".doc": $ctype="application/msword"; break; case ".xls": $ctype="application/vnd.ms-excel"; break; case ".ppt": $ctype="application/vnd.ms-powerpoint"; break; case ".gif": $ctype="image/gif"; break; case ".png": $ctype="image/png"; break; case ".jpeg": case ".jpg": $ctype="image/jpeg"; break; default: $ctype="application/force-download"; } $ContentType = sprintf("Content-Type:%s",$ctype); header($ContentType); echo $Upload_File; }
else if($_REQUEST["min"]!=null) { $fp = fopen("c:\\image.tempimage","w-"); fwrite($fp,$Upload_File); fclose($fp);
$imgresize = new resize_img(); $imgresize->sizelimit_x = 200; $imgresize->sizelimit_y = 200; $imgresize->keep_proportions = true; $imgresize->output = 'jpg'; if( $imgresize->resize_image("c:\\image.tempimage") === false) { echo 'ERROR!'; } else { $imgresize->output_resizedimage(); }
$imgresize->destroy_resizedimage(); } odbc_close($conn); return true;
?> |
最后一定要记得如果上传了比较大的图片的话，一定要在最开始的地方加入这一句，ini_set("memory_limit", "180M");
因为PHP解释器默认能够给予的memory非常小，这里设置成180M，但是实测大于10M的图片貌似还可以，再大一点的就要报错了。
