图像因其本身有错无法显示 解决方法

今天在二次开发dedecms网站时，后台地址显示验证码，发现不能正常的显示图像。IE的报错是一个×，火狐的报错是图像因其本身有错无法显示。百度一下，有种说法是“如果浏览器显示“图像XXX因其本身有错无法显示”，可尽量去掉文中空格”，作者说把空格去掉以后也没有解决办法。最后用ob_clean()清除缓冲区，成功解决此问题。现在把代码放上来供大家参考。

<?php

$config = array(
'font_size' => 14,
'img_height' => $safe_wheight,
'word_type' => (int)$safe_codetype, // 1:数字 2:英文 3:单词
'img_width' => $safe_wwidth,
'use_boder' => TRUE,
'font_file' => dirname(__FILE__).'/data/fonts/ggbi.ttf',
'wordlist_file' => dirname(__FILE__).'/data/words/words.txt',
'filter_type' => 5);
$sessSavePath = DEDEDATA."/sessions/";

// Session保存路径
if(is_writeable($sessSavePath) && is_readable($sessSavePath)){ session_save_path($sessSavePath); }
if(!empty($cfg_domain_cookie)) session_set_cookie_params(0,'/',$cfg_domain_cookie);

if (!echo_validate_image($config))
{
// 如果不成功则初始化一个默认验证码
@session_start();
$_SESSION['securimage_code_value'] = strtolower('abcd');
$im = @imagecreatefromjpeg(dirname(__FILE__).'/data/vdcode.jpg');
header("Pragma:no-cache\r\n");
header("Cache-Control:no-cache\r\n");
header("Expires:0\r\n");
imagejpeg($im);
imagedestroy($im);
}

function echo_validate_image( $config = array() )
{
@session_start();

//主要参数
$font_size = isset($config['font_size']) ? $config['font_size'] : 14;
$img_height = isset($config['img_height']) ? $config['img_height'] : 24;
$img_width = isset($config['img_width']) ? $config['img_width'] : 68;
$font_file = isset($config['font_file']) ? $config['font_file'] : PATH_DATA.'/data/font/ggbi.ttf';
$use_boder = isset($config['use_boder']) ? $config['use_boder'] : TRUE;
$filter_type = isset($config['filter_type']) ? $config['filter_type'] : 0;

//创建图片，并设置背景色
$im = @imagecreate($img_width, $img_height);
imagecolorallocate($im, 255,255,255);

//文字随机颜色
$fontColor[] = imagecolorallocate($im, 0x15, 0x15, 0x15);
$fontColor[] = imagecolorallocate($im, 0x95, 0x1e, 0x04);
$fontColor[] = imagecolorallocate($im, 0x93, 0x14, 0xa9);
$fontColor[] = imagecolorallocate($im, 0x12, 0x81, 0x0a);
$fontColor[] = imagecolorallocate($im, 0x06, 0x3a, 0xd5);

//获取随机字符
$rndstring = '';
if ($config['word_type'] != 3)
{
for($i=0; $i<4; $i++)
{
if ($config['word_type'] == 1)
{
$c = chr(mt_rand(48, 57));
} else if($config['word_type'] == 2)
{
$c = chr(mt_rand(65, 90));
if( $c=='I' ) $c = 'P';
if( $c=='O' ) $c = 'N';
}
$rndstring .= $c;
}
} else {
$fp = @fopen($config['wordlist_file'], 'rb');
if (!$fp) return FALSE;

$fsize = filesize($config['wordlist_file']);
if ($fsize < 32) return FALSE;

if ($fsize < 128)
{
$max = $fsize;
} else {
$max = 128;
}

fseek($fp, rand(0, $fsize - $max), SEEK_SET);
$data = fread($fp, 128);
fclose($fp);
$data = preg_replace("/\r?\n/", "\n", $data);

$start = strpos($data, "\n", rand(0, 100)) + 1;
$end = strpos($data, "\n", $start);
$rndstring = strtolower(substr($data, $start, $end - $start));
}

$_SESSION['securimage_code_value'] = strtolower($rndstring);

$rndcodelen = strlen($rndstring);

//背景横线
$lineColor1 = imagecolorallocate($im, 0xda, 0xd9, 0xd1);
for($j=3; $j<=$img_height-3; $j=$j+3)
{
imageline($im, 2, $j, $img_width - 2, $j, $lineColor1);
}

//背景竖线
$lineColor2 = imagecolorallocate($im, 0xda,0xd9,0xd1);
for($j=2;$j<100;$j=$j+6)
{
imageline($im, $j, 0, $j+8, $img_height, $lineColor2);
}

//画边框
if( $use_boder && $filter_type == 0 )
{
$bordercolor = imagecolorallocate($im, 0x9d, 0x9e, 0x96);
imagerectangle($im, 0, 0, $img_width-1, $img_height-1, $bordercolor);
}

//输出文字
$lastc = '';
for($i=0;$i<$rndcodelen;$i++)
{
$bc = mt_rand(0, 1);
$rndstring[$i] = strtoupper($rndstring[$i]);
$c_fontColor = $fontColor[mt_rand(0,4)];
$y_pos = $i==0 ? 4 : $i*($font_size+2);
$c = mt_rand(0, 15);
@imagettftext($im, $font_size, $c, $y_pos, 19, $c_fontColor, $font_file, $rndstring[$i]);
$lastc = $rndstring[$i];
}

//图象效果
switch($filter_type)
{
case 1:
imagefilter ( $im, IMG_FILTER_NEGATE);
break;
case 2:
imagefilter ( $im, IMG_FILTER_EMBOSS);
break;
case 3:
imagefilter ( $im, IMG_FILTER_EDGEDETECT);
break;
default:
break;
}
//解决此问题的关键，看这里，用到ob_clean()。
ob_clean();
//输出图像
header("Pragma:no-cache\r\n");
header("Cache-Control:no-cache\r\n");
header("Expires:0\r\n");

//输出特定类型的图片格式，优先级为 gif -> jpg ->png
//dump(function_exists("imagejpeg"));

if(function_exists("imagejpeg"))
{
header("content-type:image/jpeg\r\n");
imagejpeg($im);
}
else
{
header("content-type:image/png\r\n");
imagepng($im);
}
imagedestroy($im);
exit();
}

原文出处：http://www.hacktea8.com/read.php?tid-1470-ds-1.html