scatter3D保存的图片只有item模糊，且pixelRatio对item无效

[wwwkom]

One-line summary [问题简述]

scatter3D图用saveAsImage保存为png后item变得很模糊，图例和其他标签清晰，增大pixelRatio后item仍然模糊，使用 Canvas 或者 SVG 渲染效果一样。

Version & Environment [版本及环境]

• ECharts version [ECharts 版本]:
• Browser version [浏览器类型和版本]:
• OS Version [操作系统类型和版本]: echarts4

Expected behaviour [期望结果]

保存的图片整体清晰

ECharts option [ECharts配置项]

option = {

}

Other comments [其他信息]

[wwwkom]

在同一个echartsInstance中放了一个2D的scatter作为对比，发现2D的scatter分辨率可以通过pixelRatio调整，但scatter3D仍比较模糊

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.