APA102 individually addressable LEDs

Well, at the moment you have a bunch of commented out code in the FOR loop. Just removing that would help a lot (or you could turn on minification?).

Also, What happens with (bch?Math.max(bch>>4,1):0);? Would Math.max(bch>>4,0) work?

If so, make fbuf a Uint8ClampedArray and you can remove the max altogether... Maybe:

        rch*=mult;
        gch*=mult;
        bch*=mult;

        this.fbuf[i*4]=(this.ison?(gdim|224):224­);
        this.fbuf[1+i*4]=(bch?Math.max(bch>>4,1)­:0);
        this.fbuf[2+i*4]=(gch?Math.max(gch>>4,1)­:0);
        this.fbuf[3+i*4]=(rch?Math.max(rch>>4,1)­:0);

to:

var fi = 0;

        this.fbuf[fi++]=this.ison?(gdim|224):224­;
        this.fbuf[fi++]=(mult*bch)>>4;
        this.fbuf[fi++]=(mult*gch)>>4;
        this.fbuf[fi++]=(mult*rch)>>4;