PHP的GD函数imagettftext()要注意默认字符编码_PHP
这阵子在开发一个小功能，就是类似论坛个性签名的东西，根据会员信息自动生成一张图片上面还有文字的那种。图片的拼合用imagecopy()和imagecopyresampled()等函数就可以搞定，到了画文字的时候遇到了一个难题。
文字的模板是保存在一个文本文件中，程序先读取这个文件然后用数据替换掉里面的变量，再使用imagettftext()函数画到图片上，不幸的是画出来的图片居然是乱码@_@……于是上Google搜索相关的问题，发现大部分人都是在说imagettftext()函数中传递的字串要UTF-8编码，而PHP官方手册中也明确写着“UTF-8编码的字串可以直接传递”，可问题是模板文件的编码本来就是UTF-8的，这就有点莫名其妙了。无奈之下我用EmEditor打开原来的模板文件，尝试转换成不同的编码后和GD输出的乱码做对比，结果发现转换到EUC-JP编码的时候居然和GD输出的乱码吻合了……也就是说，这里服务器上GD的默认编码是EUC-JP，而那是一种日文编码。
查找了一下php.ini的设置没有发现相关选项，于是又一个问题来了，这个默认编码是在哪里设置的呢?还是史文大哥牛，发现了PHP 编译参数里面有一个“–enable-gd-jis-conv”的参数十分可疑，Google一下果然发现了很多乱码问题与这个编译参数有关……官方给出的参数说明是“GD: Enable JIS-mapped Japanese font support.”，也就是让GD支持日文编码的字库(可恶，为什么没有支持中文编码字库的编译选项……PHP也国籍歧视么= =b)，说白了开启了这个选项的话GD就会把TTF字库中大于127的部分(即不属于标准拉丁文字库的部分)按照日文JIS的顺序来映射，那么用来映射中文字体的时候自然就变成乱码了。二话不说，去掉这个选项重新编译，问题解决。去掉这个选项之后，imagettftext()的默认编码就变成了UTF- 8，就可以正常显示中文了～
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