sdfstrokes.js

// License=WTFPLv2
function exportStrokes(glyph) {
  var glArr = strokesToGlArray(glyph),
      r = [];
  for (var i = 0; i*4 < glArr.length; i ++) {
    r.push('glyph[' + i + '] = vec4('
           + glArr.slice(i*4,i*4+4).join(',') + ');');
  }
  return r.join('\n');
}
function strokeToMatrix(sk) {
    var d = Vec.sub(sk.control,sk.center),
        dsq = Vec.dot(d,d);
    if (dsq < 1E-6) {
        return [[0,0,0], [0,0,0], [0,0,0]];
    }
    var tmatrix = Matrix.inv3([
        [d[0], d[1], 0],
        [-d[1], d[0], 0],
        [sk.center[0], sk.center[1], 1]]),
        tdet = Matrix.det3(tmatrix);
    var pmatrix, result,
        mul = sk.zscale;
    switch (sk.type) {
        case 'ellipse':
            pmatrix = [
                [1,0,0],
                [0,1/sk.ratio,0],
                [0,0,-1]];
            mul /= Math.sqrt(tdet);
            break;
        case 'parabola':
            pmatrix = [
                [0, 0, sk.ratio*2],
                [0, -1, 0],
                [sk.ratio*2, 0, 0]];
            mul /= Math.sqrt(tdet);
            break;
        case 'hyperbola':
            var asq = sk.ratio*sk.ratio;
            pmatrix = [
                [asq, 0, 0],
                [0, asq-1, 0],
                [0, 0, -1]];
            mul /= tdet;
            break;
        case 'band':
            pmatrix = [
                [1, 0, 0],
                [0, 0, 0],
                [0, 0, -1]];
            mul /= Math.sqrt(tdet);
            break;
        case 'halfplane':
            pmatrix = [
                [0, 0, 0.5],
                [0, 0, 0],
                [0.5, 0, 0]];
            break;
    }
    result = Matrix.mul(Matrix.mul(tmatrix, pmatrix),
                        Matrix.transpose(tmatrix));
    return Matrix.smul(result, mul);
}

function strokesToGlArray(strokes, fillCount) {
    var result = [];
    for (var i = 0; i < strokes.length; i++) {
        var mat = strokeToMatrix(strokes[i]);
        result.push(mat[0][0]);
        result.push(mat[1][1]);
        result.push(mat[2][2]);
        result.push(mat[0][1]);
        result.push(mat[0][2]);
        result.push(mat[1][2]);
        result.push(!!strokes[i].or | (!!strokes[i].flush << 1));
        result.push(0);
    }
    for (; i < fillCount; i++) {
        for (var j = 0; j < 8; j++) {
            result.push(0);
        }
    }
    return result;
}

var Vec = {
    add: function(a,b) {
        var result = [];
        for (var i = 0; i < a.length; i++) {
            result.push(a[i]+b[i]);
        }
        return result;
    },
    sub: function(a,b) {
        var result = [];
        for (var i = 0; i < a.length; i++) {
            result.push(a[i]-b[i]);
        }
        return result;
    },
    dot: function(a,b) {
        var result = 0;
        for (var i = 0; i < a.length; i++) {
            result += a[i]*b[i];
        }
        return result;
    },
    mul: function(a, m) {
        var result = [];
        for (var i = 0; i < a.length; i++) {
            result.push(a[i]*m);
        }
        return result;
    },
};
var Matrix = {
    smul: function(a, s) {
        var result = [];
        for (var i = 0; i < a.length; i++) {
            result[i] = [];
            for (var j = 0; j < a[i].length; j++) {
                result[i][j] = a[i][j] * s;
            }
        }
        return result;
    },
    mul: function(a, b) {
        var widthA = a[0].length,
            widthB = b[0].length;
        if (widthA != b.length) {
            throw "cant haz multiply different matrices";
        }
        var result = [];
        for (var i = 0; i < a.length; i++) {
            result[i] = [];
            for (var j = 0; j < widthB; j++) {
                var sum = 0;
                for (var k = 0; k < widthA; k++) {
                    sum += a[i][k] * b[k][j];
                }
                result[i][j] = sum;
            }
        }
        return result;
    },
    transpose: function(a) {
        var result = [];
        var width = a[0].length
        for (var i = 0; i < width; i++) {
            result[i] = [];
            for (var j = 0; j < a.length; j++) {
                result[i][j] = a[j][i];
            }
        }
        return result;
    },
    det3: function(a) {
        return a[0][2]*(a[1][0]*a[2][1]-a[1][1]*a[2][0])
             + a[0][1]*(a[1][2]*a[2][0]-a[1][0]*a[2][2])
             + a[0][0]*(a[1][1]*a[2][2]-a[1][2]*a[2][1]);
    },
    inv3: function(a) {
        var det = Matrix.det3(a);
        if (Math.abs(det) < 1E-6) {
            throw 'no can inverse zero det matrix';
        }
        // eeh, who needs loops anyway?
        return Matrix.smul([
            [a[1][1]*a[2][2]-a[1][2]*a[2][1],a[0][2]*a[2][1]-a[0][1]*a[2][2],a[0][1]*a[1][2]-a[0][2]*a[1][1]],
            [a[1][2]*a[2][0]-a[1][0]*a[2][2],a[0][0]*a[2][2]-a[0][2]*a[2][0],a[0][2]*a[1][0]-a[0][0]*a[1][2]],
            [a[1][0]*a[2][1]-a[1][1]*a[2][0],a[0][1]*a[2][0]-a[0][0]*a[2][1],a[0][0]*a[1][1]-a[0][1]*a[1][0]]]
          , 1/det);
    }
};