User Manual

RAM Again

On a per-pixel basis, Adafruit_DotStarMatrix is no more memory-hungry than Adafruit_DotStar, requiring 3 bytes of

RAM per pixel. But the number of pixels in a two-dimensional display takes off exponentially…a 16x16 display requires

four times

the memory of an 8x8 display, or about 768 bytes of RAM (nearly half the available space on an Arduino

Uno). It can be anywhere from

tricky

impossible

to combine large displays with memory-hungry libraries such as SD

or ffft. Fortunately 32-bit boards (e.g. Metro Express) are fairly mainstream now.

Gamma Correction

Because the Adafruit_GFX library was originally designed for LCDs (having limited color fidelity), it handles colors as

16-bit values (rather than the full 24 bits that DotStars are capable of). This is not the big loss it might seem. A quirk of

human vision makes bright colors less discernible than dim ones. The Adafruit_DotStarMatrix library uses

gamma

correction

to select brightness levels that are visually (though not numerically) equidistant. There are 32 levels for red

and blue, 64 levels for green.

The Color() function performs the necessary conversion; you don’t need to do any math. It accepts 8-bit red, green

and blue values, and returns a gamma-corrected 16-bit color that can then be passed to other drawing functions.