raphael viewbox animated zoom

问题

I'm build a kind of javascript map with javascript and the Raphael lib. I'm able to zoom on an object when clicked, but I want it to be animated (like slowly diving in and so on). Is there a way to do so without reinventing the wheel?

回答1:

There is no reason that the viewbox of an svg object cannot be animated -- Raphael simply doesn't provide such functionality out of the box. Creating a plugin is reasonably straightforward, however. For instance:

Raphael.fn.animateViewBox = function animateViewBox( x, y, w, h, duration, easing_function, callback )
{
    var cx = this._viewBox ? this._viewBox[0] : 0,
        dx = x - cx,
        cy = this._viewBox ? this._viewBox[1] : 0,
        dy = y - cy,
        cw = this._viewBox ? this._viewBox[2] : this.width,
        dw = w - cw,
        ch = this._viewBox ? this._viewBox[3] : this.height,
        dh = h - ch,
        self = this;;
    easing_function = easing_function || "linear";

    var interval = 25;
    var steps = duration / interval;
    var current_step = 0;
    var easing_formula = Raphael.easing_formulas[easing_function];

    var intervalID = setInterval( function()
        {
            var ratio = current_step / steps;
            self.setViewBox( cx + dx * easing_formula( ratio ),
                             cy + dy * easing_formula( ratio ),
                             cw + dw * easing_formula( ratio ),
                             ch + dh * easing_formula( ratio ), false );
            if ( current_step++ >= steps )
            {
                clearInterval( intervalID );
                callback && callback();
            }
        }, interval );
}

Any paper instantiated after this plugin is installed can use animateViewBox in exactly the same method Raphael's built-in animate method works. For instance...

var paper = Raphael( 0, 0, 640, 480 );
paper.animateViewBox( 100, 100, 320, 240, 5000, '<>', function()
    {
        alert("View box updated!  What's next?" );
    } );

Demonstration staged here.

回答2:

Raphael animations work by animating element attributes. When you call element.animate, you provide the final object parameters, the time it takes to get there and possibly an easing function if you don't want it to be linear.

For example, to scale up/down an circle you might consider this example: http://jsfiddle.net/eUfCg/

// Creates canvas 320 × 200 at 10, 50
var paper = Raphael(10, 50, 320, 200);

// Creates circle at x = 50, y = 40, with radius 10
var circle = paper.circle(50, 40, 10);
// Sets the fill attribute of the circle to red (#f00)
circle.attr("fill", "#f00");

// Sets the stroke attribute of the circle to white
circle.attr("stroke", "#fff");


var zoomed = false;

circle.click(function () { 
    if (zoomed) {
        this.animate({ transform: "s1" }, 500);
        zoomed = false;
    } else {
        this.animate({ transform: "s4" }, 500);
        zoomed = true;
    }
});

Which animates the transform property of the circle. To scale your map you should put all of the elements inside a group, and animate the transform property of the group, considering the scale and translation that you want to end up with.

See http://raphaeljs.com/reference.html#Element.transform for more information on the transform property.

来源：https://stackoverflow.com/questions/13340509/raphael-viewbox-animated-zoom

标签

javascript

svg

raphael