avoid using instanceof in constructor for web worker compat
better constructor name detection
expose canvas element when possible
implement .toGray() - full-canvas grayscale conversion
use arrays instead of objects for all color calcs
always kill original ImageData in .toGray()
skip luminance and alpha composition calcs for opaque white fg and bg
speed up rgba2rgb(), create global bg setting for alpha composition
more concise logic in rgbaLumOnRgb()
inherit grayscale indicator during sectioning
.lum() now proxies .v after .toGray() is called
allows external algs to work unmodified regardless of color-mode
some var renaming
expose some internal util functions through pXY
add some inactive idea code to disable canvas scale interpolation
http://stackoverflow.com/questions/7435210/pixelated-cross-browser-image-scaling
expose pxChkr's .inRange() util function
use typed arrays in tracer
make pxTrcr worker-friendly (layers dont carry DOM dependency)
buffering funcs for workers. renamed .rec() -> recOn() for consistency
pxTrcr rewrite (unifies buffering + recording)