using jsfeat find lines in image using canny and hough

gistfile1.txt

var canvas = document.createElement('canvas');
var context2d = canvas.getContext('2d');
context2d.drawImage(img, 0, 0, width, height);
var imageData = context2d.getImageData(0, 0, pageMeta.width, pageMeta.height);
var img_u8 = new jsfeat.matrix_t(pageMeta.width, pageMeta.height, jsfeat.U8C1_t);

jsfeat.imgproc.grayscale(imageData.data, pageMeta.width, pageMeta.height, img_u8);

var r = 2;
var kernel_size = (r + 1) << 1;

jsfeat.imgproc.gaussian_blur(img_u8, img_u8, kernel_size, 0);


jsfeat.imgproc.canny(img_u8, img_u8, 100, 300);

var scaler = pageMeta.width;
if (pageMeta.height < scaler) {
    scaler = pageMeta.height;
}

scaler = scaler * .4;

var h = jsfeat.imgproc.hough_transform(img_u8, 1, (Math.PI / 540), scaler);

//At this point h really are the lines we are interested in. But im going to turn them into
//points so I can draw them on a canvas... Just for shits and grins.
var lines = [];

for (var i = 0; i < h.length; i++) {

    var rho = h[i][0];
    var theta = h[i][1];

    var a = Math.cos(theta);
    var b = Math.sin(theta);

    var x0 = a * rho;
    var y0 = b * rho;

    var pt1 = {};
    pt1.x = Math.round(x0 + 1000 * (-b));
    pt1.y = Math.round(y0 + 1000 * (a));
    var pt2 = {};
    pt2.x = Math.round(x0 - 1000 * (-b));
    pt2.y = Math.round(y0 - 1000 * (a));

    var line = {};
    line.start = pt1;
    line.end = pt2;
    lines.push(line);

}