javascript - KineticJS 如何从图层获取颜色(来自图层的颜色选择器)

Question

我有两个脚本。

首先是从图像中获取颜色:http://www.html5canvastutorials.com/labs/html5-canvas-color-picker/

 <canvas id="myCanvas" width="578" height="276"></canvas>
    <script>
      function getMousePos(canvas, evt) {
        var rect = canvas.getBoundingClientRect();
        return {
          x: evt.clientX - rect.left,
          y: evt.clientY - rect.top
        };
      }
      function drawColorSquare(canvas, color, imageObj) {
        var colorSquareSize = 100;
        var padding = 10;
        var context = canvas.getContext('2d');
        var squareX = (canvas.width - colorSquareSize + imageObj.width) / 2;
        var squareY = (canvas.height - colorSquareSize) / 2;

        context.beginPath();
        context.fillStyle = color;
        context.fillRect(squareX, squareY, colorSquareSize, colorSquareSize);
        context.strokeRect(squareX, squareY, colorSquareSize, colorSquareSize);
      }
      function init(imageObj) {
        var padding = 10;
        var canvas = document.getElementById('myCanvas');
        var context = canvas.getContext('2d');
        var mouseDown = false;

        context.strokeStyle = '#444';
        context.lineWidth = 2;

        canvas.addEventListener('mousedown', function() {
          mouseDown = true;
        }, false);

        canvas.addEventListener('mouseup', function() {
          mouseDown = false;
        }, false);

        canvas.addEventListener('mousemove', function(evt) {
          var mousePos = getMousePos(canvas, evt);
          var color = undefined;

          if(mouseDown && mousePos !== null && mousePos.x > padding && mousePos.x < padding + imageObj.width && mousePos.y > padding && mousePos.y < padding + imageObj.height) {

            // color picker image is 256x256 and is offset by 10px
            // from top and bottom
            var imageData = context.getImageData(padding, padding, imageObj.width, imageObj.width);
            var data = imageData.data;
            var x = mousePos.x - padding;
            var y = mousePos.y - padding;
            var red = data[((imageObj.width * y) + x) * 4];
            var green = data[((imageObj.width * y) + x) * 4 + 1];
            var blue = data[((imageObj.width * y) + x) * 4 + 2];
            var color = 'rgb(' + red + ',' + green + ',' + blue + ')';
            drawColorSquare(canvas, color, imageObj);
          }
        }, false);

        context.drawImage(imageObj, padding, padding);
        drawColorSquare(canvas, 'white', imageObj);
      }
      var imageObj = new Image();
      imageObj.onload = function() {
        init(this);
      };
      imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/color-picker.png';

    </script>

第二个是获取按下哪一层:http://jsfiddle.net/rws05qdr/

<div id="container"></div>
<script src="http://d3lp1msu2r81bx.cloudfront.net/kjs/js/lib/kinetic-v4.4.3.min.js"></script>
<script defer="defer">
      var stage = new Kinetic.Stage({
        container: 'container',
        width: 578,
        height: 200
      });


      var layer = new Kinetic.Layer({id:1});
      var imageObj = new Image();
      imageObj.onload = function() {
      var yoda = new Kinetic.Image({
          x: 140,
          y: stage.getHeight() / 2 - 59,
          image: imageObj,
          width: 106,
          height: 118
        });

        layer.add(yoda);
        stage.add(layer);

      };
      imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/yoda.jpg';



      var layer2 = new Kinetic.Layer({id:2});
      var imageObj2 = new Image();
      imageObj2.onload = function() {
      var filteredYoda = new Kinetic.Image({
          x: 280,
          y: stage.getHeight() / 2 - 59,
          image: imageObj2,
          width: 106,
          height: 118
        });

        layer2.add(filteredYoda);
        stage.add(layer2);
      };
      imageObj2.src = 'http://demo-stable-ofbiz.apache.org/images/products/GZ-1000/small.png';

    stage.on('click', function(e) {
        if(e.targetNode.parent.attrs.id == 1){
            alert('first layer');
        } else {
            alert('second layer');
        }
    });
</script>

我如何获得结果被图层按下并获得该图层颜色

Answer 1

getImageData(x,y,width,height) 可以从 Canvas 导出像素数据，但您正在使用“其他域”图像http://www.html5canvastutorials.com/demos/assets/yoda.jpg 和 http://demo-stable-ofbiz.apache.org/images/products/GZ-1000/small.png。它会污染 Canvas ，并且污染的 Canvas 无法导出。

您应该使用具有相同域的图像或将图像发布到支持跨域共享的网站。

解决跨域问题后，您可以使用getImageData方法。它是上下文方法，每一层都有自己的上下文。

从图层中获取上下文layer.getCanvas().getContext();并从上下文中获取鼠标位置的像素数据。

stage.on('click', function(e) {
    var x = e.pageX - $(e.target).offset().left;            // mouse position - canvas offset
    var y = e.pageY - $(e.target).offset().top;
    var ctx = e.targetNode.parent.getCanvas().getContext(); // get context from layer
    var rgb = ctx.getImageData(x, y, 1, 1).data;            // get pixel data from the context
});

这是jsfiddle:http://jsfiddle.net/rws05qdr/7/