flash as2 简易手写板，带擦除功能

//舞台上当前层需要放置名称分别为mc_bursh/mc_earse的影片剪辑
//友情提示，例子中有跟界面呈现不相关的代码，不过不影响实际功能，具体使用的时候，可以考虑酌情删减！

import flash.display.BitmapData;
import flash.geom.Rectangle;
import flash.geom.Point;
var tools = "bursh";
var widthh = 1200;
var base_point:Point = new Point(0, 0);
var base_rectangle:Rectangle = new Rectangle(0, 0, 25, 25);
var bit1:BitmapData = new BitmapData(widthh, 768, false, 0xff0000);
var org_bit:BitmapData = new BitmapData(widthh, 768, true, 0);
org_bit.draw(bit1);
var draw_bit:BitmapData = org_bit.clone();
createEmptyMovieClip("draw_mc", -999);
createEmptyMovieClip("mc1", 2);
createEmptyMovieClip("mc2", 3);
createEmptyMovieClip("mc3", 4);
drawCircle(mc1, 40, 40, 40, 0x000000);
drawCircle(mc2, 4, 4, 4, 0x000000);
mc1._visible = mc2._visible=mc3._visible=false;
draw_mc.attachBitmap(draw_bit, 1);
var erase_bit:BitmapData = new BitmapData(mc1._width, mc1._height, true, 0);
var redraw_bit:BitmapData = new BitmapData(mc2._width, mc2._height, true, 0);
erase_bit.fillRect(erase_bit.rectangle, 0xFFFFFFFF);
erase_bit.draw(mc1);
redraw_bit.draw(mc2);
erase_bit.copyChannel(erase_bit, erase_bit.rectangle, new Point(0, 0), 1, 8);
var tools:String;
earse_first();
mc_bursh.onRelease = function() {
    this.gotoAndStop(2);
    mc_earse.gotoAndStop(1);
    tools = "bursh";
};
mc_earse.onRelease = function() {
    this.gotoAndStop(2);
    mc_bursh.gotoAndStop(1);
    tools = "easre";
};
draw_mc.onPress = function() {
    if (tools == "bursh") {
        trace(1);
        mc3.moveTo(mc3._xmouse, mc3._ymouse);
        this.onMouseMove = bursh_pic;
    }
    if (tools == "easre") {
        this.onMouseMove = earse_pic;
    }
};
draw_mc.onRelease = draw_mc.onReleaseOutside=function () {
    delete this.onMouseMove;
};
function earse_pic() {
    mc3.clear();    var now_rect:Rectangle = new Rectangle(_xmouse-mc1._width/2, _ymouse-mc1._width/2, _xmouse+base_rectangle.width, _ymouse+base_rectangle.height);
    draw_bit.copyPixels(draw_bit, now_rect, new Point(_xmouse-mc1._width/2, _ymouse-mc1._width/2), erase_bit, new Point(0, 0), false);
    updateAfterEvent();
}
function earse_first() {
    var now_rect:Rectangle = new Rectangle(0, 0, widthh, 768);
    draw_bit.copyPixels(draw_bit, now_rect, new Point(0, 0), new BitmapData(widthh, 768, true, 0x0), new Point(0, 0), false);
    updateAfterEvent();
}
function bursh_pic() {
    trace(mc3);
    mc3.lineStyle(8, 0xff0000, 100);
    mc3.lineTo(mc3._xmouse, mc3._ymouse);
    draw_bit.draw(mc3);
    draw_mc.attachBitmap(draw_bit, 1);
    //var now_rect:Rectangle = new Rectangle(_xmouse, _ymouse, _xmouse+base_rectangle.width, _ymouse+base_rectangle.height);
    //draw_bit.copyPixels(org_bit, now_rect, new Point(_xmouse-mc2._width/2, _ymouse-mc2._width/2), redraw_bit, new Point(0, 0), true);
    //updateAfterEvent();
}
function drawCircle(mc:MovieClip, x:Number, y:Number, r:Number, color:Number):Void {
    mc.beginFill(color);
    mc.moveTo(x+r, y);
    mc.curveTo(r+x, Math.tan(Math.PI/8)*r+y, Math.sin(Math.PI/4)*r+x, Math.sin(Math.PI/4)*r+y);
    mc.curveTo(Math.tan(Math.PI/8)*r+x, r+y, x, r+y);
    mc.curveTo(-Math.tan(Math.PI/8)*r+x, r+y, -Math.sin(Math.PI/4)*r+x, Math.sin(Math.PI/4)*r+y);
    mc.curveTo(-r+x, Math.tan(Math.PI/8)*r+y, -r+x, y);
    mc.curveTo(-r+x, -Math.tan(Math.PI/8)*r+y, -Math.sin(Math.PI/4)*r+x, -Math.sin(Math.PI/4)*r+y);
    mc.curveTo(-Math.tan(Math.PI/8)*r+x, -r+y, x, -r+y);
    mc.curveTo(Math.tan(Math.PI/8)*r+x, -r+y, Math.sin(Math.PI/4)*r+x, -Math.sin(Math.PI/4)*r+y);
    mc.curveTo(r+x, -Math.tan(Math.PI/8)*r+y, r+x, y);
    mc.endFill();
}