EaselJS:拖动蒙版时使用带有AlphaMaskFilter的updateCache()

时间:2013-04-05 21:02:09

标签: html5-canvas masking createjs

我正在使用带有alpha渐变的导入的png,我将其设置为遮罩,显示分配给它的位图。掩模对象是可拖动的(有点像手电筒)。我知道我应该使用AlphaMaskFilter作为过滤器之一,我知道我应该使用.updateCache()......我只是不确定我是否正确使用它们?

var stage;
var assetQueue;
var bg;
var bgMask;
var container;
var amf;

$(document).ready(function(){
    loadImages();

});

function loadImages()
{

    // Set up preload queue
    assetQueue = new createjs.LoadQueue();


    assetQueue.addEventListener("complete", preloadComplete);
    assetQueue.loadManifest([{id:"img_bg",src:"images/Nintendo-logo-red.jpg"}, {id:"img_bg_mask",src:"images/background_mask.png"}]);
}

function preloadComplete()
{
    assetQueue.removeEventListener("complete", preloadComplete);

    init();
}

function init()
{
    stage = new createjs.Stage("stage_canvas");

    setBackgrounds();

    sizeStage();

    $(document).mousemove(function(evt){
        trackMouse(evt);
    });
}

function trackMouse(evt)
{
    var mouseX = evt.pageX;
    var mouseY = evt.pageY;

    // Move the containing clip around
    container.x = mouseX - (bgMask.image.width / 2);
    container.y = mouseY - (bgMask.image.height / 2);


    // Offset the position of the masked image.
    bg.x = -container.x;
    bg.y = -container.y;

    container.updateCache();
    stage.update();
}

function setBackgrounds()
{   
    bg = new createjs.Bitmap(assetQueue.getResult("img_bg"));
    bgMask = new createjs.Bitmap(assetQueue.getResult("img_bg_mask"));
    container = new createjs.Container();

    container.addChild(bg);
    amf = new createjs.AlphaMaskFilter(bgMask.image)
    container.filters = [amf];

    container.cache(0, 0, bg.image.width, bg.image.height);

    stage.addChild(container);

    stage.update();
}

function sizeStage()
{

    var windowW = 600;
    var windowH = 600;

    stage.canvas.width = windowW;
    stage.canvas.height = windowH;

    stage.update();
}

1 个答案:

答案 0 :(得分:2)

发现解决方案(对任何感兴趣的人)。关键是将要屏蔽的图像添加到容器中。将容器移动到所需的任何位置,然后偏移容器中包含的图像。代码已更新以反映这一点。