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<?php
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session_start();
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$image = imagecreatetruecolor(100, 38); //1>设置验证码图片大小的函数
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//5>设置验证码颜色 imagecolorallocate(int im, int red, int green, int blue);
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$bgcolor = imagecolorallocate($image,255,255,255); //#ffffff
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//6>区域填充 int imagefill(int im, int x, int y, int col) (x,y) 所在的区域着色,col 表示欲涂上的颜色
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imagefill($image, 0, 0, $bgcolor);
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//10>设置变量
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$captcha_code = "";
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//7>生成随机数字
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for($i=0;$i<4;$i++){
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//设置字体大小
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$fontsize = 8;
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//设置字体颜色，随机颜色
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$fontcolor = imagecolorallocate($image, rand(0,120),rand(0,120), rand(0,120)); //0-120深颜色
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//设置数字
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$fontcontent = rand(0,9);
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//10>.=连续定义变量
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$captcha_code .= $fontcontent;
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//设置坐标
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$x = ($i*100/4)+rand(5,10);
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$y = rand(5,10);
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imagestring($image,$fontsize,$x,$y,$fontcontent,$fontcolor);
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}
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//10>存到session
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$_SESSION['authcode'] = $captcha_code;
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//8>增加干扰元素，设置雪花点
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for($i=0;$i<30;$i++){
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//设置点的颜色，50-200颜色比数字浅，不干扰阅读
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$pointcolor = imagecolorallocate($image,rand(50,200), rand(50,200), rand(50,200));
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//imagesetpixel — 画一个单一像素
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imagesetpixel($image, rand(1,99), rand(1,29), $pointcolor);
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}
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//9>增加干扰元素，设置横线
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for($i=0;$i<3;$i++){
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//设置线的颜色
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$linecolor = imagecolorallocate($image,rand(80,220), rand(80,220),rand(80,220));
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//设置线，两点一线
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imageline($image,rand(1,99), rand(1,29),rand(1,99), rand(1,29),$linecolor);
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}
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//2>设置头部，image/png
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header('Content-Type: image/png');
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//3>imagepng() 建立png图形函数
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imagepng($image);
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//4>imagedestroy() 结束图形函数 销毁$image
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imagedestroy($image);
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