Matlab Clustergram Image increase resolution

I read multiple official and non-official solutions but none worked as mine:

1. plug in your computer to a second screen which is much bigger
2. drag to enlarge the plot area
3. if the dendrogram tree partially disappears, the solution is: edit -> axis property, to open the property window, and then close it.

4. save to bmp file. I got a bmp image of 50MB