在 KineticJS 中缩放到固定点

Question

我在将容器缩放到固定点时遇到了一些问题。
就我而言，我正在尝试将舞台缩放（缩放）到鼠标光标。

这是一种使用纯画布的方法： http://phrogz.net/tmp/canvas_zoom_to_cursor.html（在Zoom Canvas to Mouse Cursor 讨论过）

我只是不知道如何在使用 KineticJS API 时应用相同的逻辑。

示例代码：

var position = this.stage.getUserPosition();
var scale = Math.max(this.stage.getScale().x + (0.05 * (scaleUp ? 1 : -1)), 0);
this.stage.setScale(scale);
// Adjust scale to position...?
this.stage.draw();

Answer 1

您需要偏移舞台，使其中心点位于固定点。这是一个例子，因为舞台的中心点默认在画布的左上角。假设您的舞台宽 600 像素，高 400 像素，并且您希望舞台从中心缩放。你需要这样做：

var stage = new Kinetic.Stage({
   container: 'container',
   width: 600,
   height: 400,
   offset: [300, 200]
};

Answer 2

经过大量的挣扎、搜索和尝试，使用@Eric Rowell 提供的提示和 SO 问题Zoom in on a point (using scale and translate) 中发布的代码，我终于使用KineticJS 放大和缩小了一个固定点。

这是一个有效的DEMO。

这是代码：

var ui = {
    stage: null,
    scale: 1,
    zoomFactor: 1.1,
    origin: {
        x: 0,
        y: 0
    },
    zoom: function(event) {
        event.preventDefault();
        var evt = event.originalEvent,
            mx = evt.clientX /* - canvas.offsetLeft */,
            my = evt.clientY /* - canvas.offsetTop */,
            wheel = evt.wheelDelta / 120;
        var zoom = (ui.zoomFactor - (evt.wheelDelta < 0 ? 0.2 : 0));
        var newscale = ui.scale * zoom;
        ui.origin.x = mx / ui.scale + ui.origin.x - mx / newscale;
        ui.origin.y = my / ui.scale + ui.origin.y - my / newscale;

        ui.stage.setOffset(ui.origin.x, ui.origin.y);
        ui.stage.setScale(newscale);
        ui.stage.draw();

        ui.scale *= zoom;
    }
};

$(function() {
    var width = $(document).width() - 2,
        height = $(document).height() - 5;
    var stage = ui.stage = new Kinetic.Stage({
        container: 'container',
        width: width,
        height: height
    });
    var layer = new Kinetic.Layer({
        draggable: true
    });
    var rectX = stage.getWidth() / 2 - 50;
    var rectY = stage.getHeight() / 2 - 25;

    var box = new Kinetic.Circle({
        x: 100,
        y: 100,
        radius: 50,
        fill: '#00D200',
        stroke: 'black',
        strokeWidth: 2,
    });

    // add cursor styling
    box.on('mouseover', function() {
        document.body.style.cursor = 'pointer';
    });
    box.on('mouseout', function() {
        document.body.style.cursor = 'default';
    });

    layer.add(box);
    stage.add(layer);

    $(stage.content).on('mousewheel', ui.zoom);
});​

Answer 3

更新了@juan.facorro 的演示以缩放形状而不是舞台

jsFiddle

var ui = {
    stage: null,
    box: null,
    scale: 1,
    zoomFactor: 1.1,
    zoom: function(event) {
        event.preventDefault();
        var evt = event.originalEvent,
            mx = evt.offsetX,
            my = evt.offsetY,
            wheel = evt.wheelDelta / 120; //n or -n
        var zoom = (ui.zoomFactor - (evt.wheelDelta < 0 ? 0.2 : 0));
        var newscale = ui.scale * zoom;

        var origin = ui.box.getPosition();
        origin.x = mx - (mx - origin.x) * zoom;
        origin.y = my - (my - origin.y) * zoom;

        ui.box.setPosition(origin.x, origin.y);
        ui.box.setScale(newscale);
        ui.stage.draw();

        ui.scale *= zoom;
    }
};

$(function() {
    var width = $(document).width() - 2,
        height = $(document).height() - 5;
    var stage = ui.stage = new Kinetic.Stage({
        container: 'container',
        width: width,
        height: height
    });
    var layer = new Kinetic.Layer();
    var rectX = stage.getWidth() / 2 - 50;
    var rectY = stage.getHeight() / 2 - 25;

    var box = ui.box = new Kinetic.Circle({
        x: 100,
        y: 100,
        radius: 50,
        fill: '#00D200',
        stroke: 'black',
        strokeWidth: 2,
        draggable: true
    });

    // add cursor styling
    box.on('mouseover', function() {
        document.body.style.cursor = 'pointer';
    });
    box.on('mouseout', function() {
        document.body.style.cursor = 'default';
    });

    layer.add(box);
    stage.add(layer);

    $(stage.content).on('mousewheel', ui.zoom);
});

Answer 4

上面的演示只有在舞台的 x 和 y 坐标为 0 时才有效。例如舞台是可拖动的，它会在拖动时更改这些坐标，因此它们需要包含在偏移计算中。这可以通过从画布偏移中减去它们来实现：

jsfiddle

zoom: function(event) {
    event.preventDefault();
    var evt = event.originalEvent,
        mx = evt.offsetX - ui.scale.getX(),
        my = evt.offsetY - ui.scale.getY(),
    var zoom = (ui.zoomFactor - (evt.wheelDelta < 0 ? 0.2 : 0));
    var newscale = ui.scale * zoom;

    var origin = ui.box.getPosition();
    origin.x = mx - (mx - origin.x) * zoom;
    origin.y = my - (my - origin.y) * zoom;

    ui.box.setPosition(origin.x, origin.y);
    ui.box.setScale(newscale);
    ui.stage.draw();

    ui.scale *= zoom;
}