As can be noticed in bar-graph-too-large.png, the graph is clearly too big for the amount of information to be displayed.
Graphs are included in reports & mobile using a fixed size by setting width & height to appropriate values.
It would bring to much complexity to delegate size adjustment to ImageGraph API clients.
Therefore, the ImageGraph plugin could automatically add padding to effectively reduce the graph size.
Great request! I think it's a must have +1