在KineticJS中缩放到固定点 [英] Scaling to a fixed point in KineticJS

问题描述

我在将容器缩放到固定点时遇到一些问题。

在我的示例中，我尝试将一个阶段缩放（缩放）为鼠标光标。

I'm having some problems with scaling a container to a fixed point.
In my case I'm trying to scale (zoom) a stage to the mouse cursor.

这是一种使用纯画布的方法：
http://phrogz.net /tmp/canvas_zoom_to_cursor.html （如缩放画布到鼠标光标）

Here is a way to do with pure canvas: http://phrogz.net/tmp/canvas_zoom_to_cursor.html (as discussed at Zoom Canvas to Mouse Cursor)

在使用KineticJS API的时候，我不知道如何应用相同的逻辑。

I just can't get figure out how to apply the same logic while using the KineticJS API.

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();

推荐答案

经过很多挣扎，搜索和尝试，由 @Eric Rowell 提供的提示以及SO问题中发布的代码缩放点（使用缩放和翻译）我终于得到放大和缩小使用 KineticJS 工作的固定点。

After a lot of struggling and searching and trying, using the tip provided by @Eric Rowell and the code posted in the SO question Zoom in on a point (using scale and translate) I finally got the zooming in and out of a fixed point working using KineticJS.

这是一个有效的 DEMO 。

这里是代码：

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);
});​

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