tile.js

var x = scroll.x;
        var y = scroll.y;
        var minX = undefined, maxX = undefined;
        var minY = undefined, maxY = undefined;
        if(x < 0) {
            while(x < paisley.width) {
                if(x > -paisley.width) {
                    if(minX === undefined) {
                        minX = x;
                    }
                }
                x += paisley.width;
            }
            maxX = x;
        } else {
            while(x > -paisley.width) {
                if(x < paisley.width) {
                    if(maxX === undefined) {
                        maxX = x;
                    }
                }
                x -= paisley.width;
            }
            minX = x;
        }
        if(y < 0) {
            while(y < paisley.height) {
                if(y > -paisley.height) {
                    if(minY === undefined) {
                        minY = y;
                    }
                }
                y += paisley.height;
            }
            maxY = y;
        } else {
            while(y > -paisley.height) {
                if(y < paisley.height) {
                    if(maxY === undefined) {
                        maxY = y;
                    }
                }
                y -= paisley.height;
            }
            minY = y;
        }
        while(minX <= maxX) {
            var y = minY;
            while(y <= maxY) {
                ctx.drawImage(paisley, minX, y);
                y += paisley.height;
            }
            minX += paisley.width;
        }