完整错误信息：

Tesseract Open Source OCR Engine v3.04.00 with Leptonica Error opening data file /usr/local/share/tessdata/eng.traineddata Please make sure the TESSDATA_PREFIX environment variable is set to the parent directory of your “tessdata” directory. Failed loading language ‘eng’ Tesseract couldn’t load any languages! Could not initialize tesseract.

注意加粗部分字体，显示在/usr/local/share/tessdata目录下找不到eng语言包。

原来是安装语言包的时候安装到了tesseract的安装目录下，而使用的时候它去/usr/local/share/tessdata找了。那么把tesseract的安装目录下语言包移到/usr/local/share/tessdata就可以了：

mv tessdata/eng.traineddata /usr/local/share/tessdata