body中的数据格式：
/**
* Convert text to PNG image.
* @param text
* @param [options]
* @param [options.font="30px sans-serif"] css style font
* @param [options.textAlign="left"] text alignment (left, center, right)
* @param [options.color="black"] (or options.textColor) text color
* @param [options.backgroundColor] (or options.bgColor) background color
* @param [options.lineSpacing=0]
* @param [options.strokeWidth=0]
* @param [options.strokeColor='white']
* @param [options.padding=0] width of the padding area (left, top, right, bottom)
* @param [options.paddingLeft]
* @param [options.paddingTop]
* @param [options.paddingRight]
* @param [options.paddingBottom]
* @param [options.borderWidth=0] width of border (left, top, right, bottom)
* @param [options.borderLeftWidth=0]
* @param [options.borderTopWidth=0]
* &#
