Feature Request: dynamic image sizes

[njh]

The RadioVIS specification supports specifying the size of the screen / requested image size:

Devices are recommended to include the following HTTP headers in their request when acquiring images from a URL, indicating the display dimensions and resolution density of the device. This is to assist in returning a more appropriate resource for that device.

Header Name	Description	Mandatory
Display-Height	Visible device screen height, in pixels	No (default is 240 pixels)
Display-Width	Visible device screen width, in pixels	No (default is 320 pixels)
Display-PPI	Visible device pixel density, in pixels per inch (PPI)	No (default is 72 PPI)

It would be useful if the demo app supported this.