How to Change Color of Symbols in PaperJs

Question

I don't know how to create a jsfiddle for Paper.js since I keep getting "domain policy" restrictions; but you can test by going here and clicking run: http://paperjs.org/tutorials/animation/creating-animations/#moving-multiple-items

I have the following code:

// The amount of circles we want to make:
var count = 50;

// Create a symbol, which we will use to place instances of later:
var point = new Point(20, 20);
var size = new Size(60, 60);

var path = new Path.Rectangle({
    point: point,
    size: size,
    fillColor: 'grey',
    strokeColor: 'black'
});

var symbol = new Symbol(path);

// Place the instances of the symbol:
for (var i = 0; i < count; i++) {
    // The center position is a random point in the view:
    var center = Point.random() * view.size;
    var placedSymbol = symbol.place(center);
    var placedSymbol = symbol.place(center);
    placedSymbol.scale(i / count);

    if (i % 5 == 0) {
        placedSymbol.style = {
            fillColor: new Color(1, 0, 0),
            strokeColor: 'black',
            strokeWidth: 5
        };
    }
}

console.log(project.activeLayer.children[0]);

// The onFrame function is called up to 60 times a second:
function onFrame(event) {
    // Run through the active layer's children list and change
    // the position of the placed symbols:
    for (var i = 0; i < count; i++) {
        var item = project.activeLayer.children[i];

        // Move the item 1/20th of its width to the right. This way
        // larger circles move faster than smaller circles:
        item.position.x += item.bounds.width / 100;

        //if (i % 5 == 0)
            //item.fillColor = new Color(1, 0, 0);

        // If the item has left the view on the right, move it back
        // to the left:
        if (item.bounds.left > view.size.width) {
            item.position.x = -item.bounds.width;
        }
    }
}

I know I can just change the color of the path like this:

var path = new Path.Rectangle({
    point: point,
    size: size,
    fillColor: 'grey',
    strokeColor: 'black'
});

But, I want to change the color of only specific rectangles which are divisible by five:

if (i % 5 == 0) {
    placedSymbol.style = {
        fillColor: new Color(1, 0, 0),
        strokeColor: 'black',
        strokeWidth: 5
    };
}

But, the fill color never changes! What is the proper way to change the fill color/ style of only certain symbols?

Answer 1

The answer for me was to not use symbols at all, just use paths like so:

// The amount of circles we want to make:
var count = 150;

// Create a symbol, which we will use to place instances of later:


// Place the instances of the symbol:
for (var i = 0; i < count; i++) {
    // The center position is a random point in the view:
    var path = new Path.Circle({
        center: Point.random() * view.size,
        radius: i / count + 0.5,
        fillColor: 'white',
        strokeColor: 'black'
    });
    if (i % 10 == 0)
        path.style.fillColor = '#eee';
}

// The onFrame function is called up to 60 times a second:
function onFrame(event) {
    // Run through the active layer's children list and change
    // the position of the placed symbols:
    for (var i = 0; i < count; i++) {
        var item = project.activeLayer.children[i];

        // Move the item 1/20th of its width to the right. This way
        // larger circles move faster than smaller circles:
        item.position.x += item.bounds.width / 300;

        // If the item has left the view on the right, move it back
        // to the left:
        if (item.bounds.left > view.size.width) {
            item.position.x = -item.bounds.width;
        }
    }
}

Answer 2

This is a duplicate. Someone gave the right answer over there:

This is by design. You cannot change the visual properties of an instance of a Symbol. To change the color of the item, you can create multiple copies of the path by using path.clone().