PDF Text文本显示

PDF中以BT开始一个text object， 以ET结束一个text object， BT和ET不能嵌套。


Text-Showing Operators
Tj              show a text string
'               Move to the next line and show a text string
''              Move to the next line and show a text string
TJ              Show one or more text strings, allowing individual glyph positionsiong.