In answer to your questions:
– The image size and quality itself is just as important as the printer – the larger the size you want to print at, the greater the dimensions your image needs to have. The only exception to this is with “vector” images, which Ribbet doesn’t support.
– The DPI issue can be confusing, but to simplify, here’s the equation:
Image dimensions = (width in inches x DPI) x (height in inches x DPI)
So, for example if you want to print at 4ftx4ft at 700DPI, your image would need to be:
(48×700) x (48×700)
= 33600 x 33600
This is an extraordinarily large image though, and Ribbet is only capable of dimensions up to 16 megapixels (4000 x 4000) which is approximately 13.3″ x 13.3″ at 300DPI.
I would ask your printer if a 4000×4000 pixel image will be large enough. If it is you can create your Blank Canvas at this dimension. If not, you unfortunately won’t be able to use Ribbet for this project.
Let us know if you have any other questions.