- used to parse pdf and extract text
- represent the block merge text using simple matrix calculate
- 可以有偿提供 PDF 去水印服务，具体联系 hy05190134@qq.com
- realize the same format with the origin pdf document
- parallel extract the text, promote 30% performance (√)
- full use the design of schedule of golang and optimise string join, promote 30% performance (√)