Try to reduce lines count on pictures with more white dot

[huozhi]

The first picture of portrait is full of gray dots. Its result seems quite natural.
The second picture of logo contains much more pure white dots. 1500 lines maybe a little bit redundant that makes the result darker.

[fanqieo]

@huozhi I can't run， It's not missing two documents. svg.js，zepto.js is non-existent