well, the icons I've made are either single-color or two-color. Yes. But I have tried just making them monochrome and using Adafruit's drawBitmap function, and I wasn't happy with the results at all.
Here's what I've got so far:
They key is anti-aliasing. Even images and icons that were made deliberately using just one single color will look better anti-aliased, with smoothed edges. Anti-aliasing makes font characters and icons "blend in" with their surroundings, and edges in particular appear less rough and blocky than they would as a monochrome one-byte bitmap.
The twist is that anti-aliasing requires full-color pixel definition, or, in the case of black, at least grayscale.
Here's another look at a typical user interface submenu screen as I envision it:
When displayed values reach critical levels (e.g. less than 5 liters left in the fuel tank, or maybe an oil temperature above 120°C), the digits will appear in red. In addition to displaying a fullscreen warning message once for five seconds. So I will also need an array of "red" digits bitmaps.
Also, when one of the more safety-relevant warnings has been triggered (fuel, lights, oil temp, coolant temp, battery voltage), a corresponding icon will be displayed in the bottom row of the display, under the red horizontal line, and it will take turns every five seconds with the interior and exterior air temperatures that are normally displayed there.
I know that I am not making it easy on myself. But frankly, when comparing the results, there is no doubt in my mind that I want everything on my screen anti-aliased. Even if that will require practically writing my own miniature font library for the number digits.
Using actual monochrome would be easier to code and it would take less time too. But at the end of the day, the Adafruit display [u]is[/u] capable of what I've got in mind for it. And to me, even if it takes longer to achieve, that's what matters. I might have to teach myself a good number of things yet before getting there, but hey, to me, that's part of the fun. And my personal finishing deadline for this CarDuino isn't until next summer anyway, so I've got plenty of time to spend on these things still. ;)