29a.ch - Jonas Wagner's Blog

// flip x axis
ctx.scale(-1, 1);
ctx.drawImage(img, x, y);
// flip it back again
ctx.scale(-1, 1);

// randomize a variable
function fuzz(x, f){
    return x + Math.random()*f - f/2;
}

// estimate the movement of the arm
// x0: start
// x1: end
// t: step from 0 to 1
function handDrawMovement(x0, x1, t){
    return x0 + (x0-x1)*(
            15*Math.pow(t, 4) -
            6*Math.pow(t, 5) -
            10*Math.pow(t,3)
    )
}

// hand draw a circle
// ctx: Context2D
// x, y: Coordinates
// r: radius
function handDrawCircle(ctx, x, y, r){
    var steps = Math.ceil(Math.sqrt(r)*3);

    // fuzzyness dependent on radius
    var f = 0.12*r;

    // distortion of the circle
    var xs = 1.0+Math.random()*0.1-0.05;
    var ys = 2.0-xs;

    ctx.moveTo(x+r*xs, y);

    for(var i = 1; i <= steps; i++)
    {
        var t0 = (Math.PI*2/steps)*(i-1);
        var t1 = (Math.PI*2/steps)*i;
        var x0 = x+Math.cos(t0)*r*xs;
        var y0 = y+Math.sin(t0)*r*ys;
        var x1 = x+Math.cos(t1)*r*xs;
        var y1 = y+Math.sin(t1)*r*ys;

        ctx.quadraticCurveTo(fuzz(x0, f), fuzz(y0, f), x1, y1);
        ctx.moveTo(x1, y1);
    }
}

// inspired by this paper http://iwi.eldoc.ub.rug.nl/FILES/root/2008/ProcCAGVIMeraj/2008ProcCAGVIMeraj.pdf
function handDrawLine(ctx, x0, y0, x1, y1){
    ctx.moveTo(x0, y0)

    var d = Math.sqrt((x1-x0)*(x1-x0)+(y1-y0)*(y1-y0))

    var steps = d/25;
    if(steps < 4) {
        steps = 4;
    }

    // fuzzyness
    var f = 8.0;
    for(var i = 1; i <= steps; i++)
    {
        var t1 = i/steps;
        var t0 = t1-1/steps
        var xt0 = handDrawMovement(x0, x1, t0)
        var yt0 = handDrawMovement(y0, y1, t0)
        var xt1 = handDrawMovement(x0, x1, t1)
        var yt1 = handDrawMovement(y0, y1, t1)
        ctx.quadraticCurveTo(fuzz(xt0, f), fuzz(yt0, f), xt1, yt1)
        ctx.moveTo(xt1, yt1)
    }
}

# convert opensolo.mid to fluidsynth.raw using the soundfont /usr/share/sounds/sf2/FluidR3_GM.sf2 
fluidsynth -l -i -a file -z 2048 /usr/share/sounds/sf2/FluidR3_GM.sf2 opensolo.mid
# convert fluidsynth.raw to fluidsynth.wav using sox
sox -b 16 -c 2 -s -r 44100 fluidsynth.raw fluidsynth.wav