javascript - Raphael JS 高效实现 "Pencil"工具

Question

我正在做一个项目，要求最终用户能够在浏览器中绘图，就像 svg-edit并将SVG数据发送给服务器进行处理。

我开始玩 Raphael框架，看起来很有希望。

目前我正在尝试实现铅笔或自由线类型的工具。基本上我只是根据绘图区域中鼠标移动的百分比绘制一条新路径。然而，最终这将创建大量的路径来处理。

Is it possible to shorten an SVG path by converting mouse movement to use Curve and Line paths instead of line segments?

下面是我为完成这项工作而草拟的代码草稿......

    // Drawing area size const
   var SVG_WIDTH = 620;
   var SVG_HEIGHT = 420;

   // Compute movement required for new line
   var xMove = Math.round(SVG_WIDTH * .01);
   var yMove = Math.round(SVG_HEIGHT * .01);

   // Min must be 1
   var X_MOVE = xMove ? xMove : 1;
   var Y_MOVE = yMove ? yMove : 1;

   // Coords
   var start, end, coords = null;
   var paperOffset = null;
   var mouseDown = false;

   // Get drawing area coords
   function toDrawCoords(coords) {
    return {
     x: coords.clientX - paperOffset.left,
     y: coords.clientY - paperOffset.top
    };
   }

   $(document).ready(function() {
    // Get area offset
    paperOffset = $("#paper").offset();
    paperOffset.left = Math.round(paperOffset.left);
    paperOffset.top = Math.round(paperOffset.top);
    // Init area
    var paper = Raphael("paper", 620, 420);
    // Create draw area
    var drawArea = paper.rect(0, 0, 619, 419, 10)
    drawArea.attr({fill: "#666"});

    // EVENTS
    drawArea.mousedown(function (event) {
     mouseDown = true;
     start = toDrawCoords(event);
     $("#startCoords").text("Start coords: " + $.dump(start));
    });
    drawArea.mouseup(function (event) {
     mouseDown = false;
     end = toDrawCoords(event);
     $("#endCoords").text("End coords: " + $.dump(end));
     buildJSON(paper);
    });
    drawArea.mousemove(function (event) {
     coords = toDrawCoords(event);
     $("#paperCoords").text("Paper coords: " + $.dump(coords));
     // if down and we've at least moved min percentage requirments
     if (mouseDown) {
      var xMovement = Math.abs(start.x - coords.x);
      var yMovement = Math.abs(start.y - coords.y);
      if (xMovement > X_MOVE || yMovement > Y_MOVE) {
       paper.path("M{0} {1}L{2} {3}", start.x, start.y, coords.x, coords.y);
       start = coords; 
      }
     }
    });


   }); 

Answer 1

查看 Douglas-Peucker 算法以简化您的生产线。

我不知道任何 javascript 实现(尽管谷歌搜索将我引导到谷歌地图开发者论坛)但这里有一个很容易理解的 tcl 实现:http://wiki.tcl.tk/27610

这里有一篇解释该算法的维基百科文章(连同伪代码):http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm