Question

我对blitting很新，我还在努力理解这个过程。在我的View对象中，我在构造函数中有这个;

this.bcg = new BitmapData(800,600,false,0x000000);
this.canvas = new Bitmap(bcg);

然后我将它添加到舞台上;

addChild(canvas);

然后在我的主游戏循环中，我遍历一个嵌套数组来blit rect类型BitmapData对象的副本;

if (array[i][j] !=0) {
        canvas.bitmapData.copyPixels(rect, rect.rect, new Point(i, j));
}

我想也许我可以通过在我的循环之前将背景blit到canvas来做到这一点;

canvas.bitmapData.copyPixels(bcg, bcg.rect, new Point(0, 0));

但这不起作用。我已经尝试过寻找答案，但是很难找到有关AS3中blitting的任何深入信息。

我要做的是清除所有像素的位图，然后再用我的背景bcg重新开始。我在循环之前尝试过这样做;

this.bcg = new BitmapData(800,600,false,0x000000);
this.canvas = new Bitmap(bcg);

但我最终得到了一个完全黑屏，而我的rect都没有被canvas点缀。

Answer 1

这是一个简单的blitting示例：

private var m_bg:BitmapData         = new BitmapData( 400, 300, false, 0xffff0000 );    // simple solid red colour
private var m_canvas:BitmapData     = new BitmapData( 400, 300, true, 0x00000000 );     // the canvas that we're drawing into
private var m_obj:BitmapData        = new BitmapData( 20, 20, false, 0xff00ff00 );      // simple green square
private var m_objDrawPos:Point      = new Point;                                        // where we'll draw our obj
private var m_objDir:Point          = new Point;                                        // the direction that our obj is moving in
private var m_objSpeed:Number       = 20.0;                                             // the speed of our obj

public function Main()
{
    // create the bitmap for our canvas and add it to the stage
    var b:Bitmap = new Bitmap( this.m_canvas );
    this.addChild( b );

    // set our initial direction
    this.m_objDir.setTo( 1.0, 1.0 ); // diagonal right

    // add our enter frame
    this.addEventListener( Event.ENTER_FRAME, this._onEnterFrame );
}

private function _onEnterFrame( e:Event ):void
{
    // move our object by changing it's draw position
    this.m_objDrawPos.x += this.m_objDir.x * this.m_objSpeed;
    this.m_objDrawPos.y += this.m_objDir.y * this.m_objSpeed;

    // simple bounds change, to reflect the object
    if ( this.m_objDrawPos.x < 0 || this.m_objDrawPos.x + this.m_obj.width > this.m_canvas.width )
        this.m_objDir.x *= -1;
    if ( this.m_objDrawPos.y < 0 || this.m_objDrawPos.y + this.m_obj.height > this.m_canvas.height )
        this.m_objDir.y *= -1;

    // copy our this.m_bg - this will erase all previous changes
    // NOTE: depending on what your bg is, you can all use fillRect() if it's a solid colour
    // NOTE: passing new Point() as the destPoint, will mean that our bg will always be drawn
    // in the top-left of the canvas. As this never changes - you can keep this as a variable
    this.m_canvas.copyPixels( this.m_bg, this.m_bg.rect, new Point );

    // copy our object to its new position
    this.m_canvas.copyPixels( this.m_obj, this.m_obj.rect, this.m_objDrawPos );
}

关于blitting需要了解的是，它是destPoint传入的位置，它确定了BitmapData的左上角位置 - 将其视为{正常x - y的{1}}和DisplayObject意味着它在左上角绘制，而(0,0)意味着它在右下角绘制。

为了让您的生活更轻松，请创建一个简单的类来为您存储所有这些数据。类似的东西：

(canvas.width - obj.width, canvas.height - obj.height)

在blitting时要注意一件事，而这个类就是这样，它处理public class BlitObj { /************************************************************/ private var m_bmd:BitmapData = null; // our BitmapData graphics private var m_offset:Point = null; // the offset (how we manage the reference point) private var m_drawPos:Point = null; // our draw position for when we're blitting the object private var m_position:Point = null; // the position of our object, in relation to the reference point /************************************************************/ /** * The position of the BlitObj, in relation to the reference point */ public function get position():Point { return this.m_position; } /** * The BitmapData graphics that we're going to blit */ public function get blitGraphics():BitmapData { return this.m_bmd; } /** * The position to blit this BlitObj at (top-left corner) */ public function get blitDestPos():Point { return this.m_drawPos; } /************************************************************/ /** * Creates a new BlitObj * @param bmd The graphics for this BlitObj * @param offset The offset to our registration point */ public function BlitObj( bmd:BitmapData, offset:Point = null ) { this.m_bmd = bmd; this.m_offset = ( offset == null ) ? new Point : offset; this.m_drawPos = new Point( -this.m_offset.x, -this.m_offset.y ); this.m_position = new Point; } /** * Sets the position of the BlitObj (in relation to its reference point) * @param x The x position of the object * @param y The y position of the object */ public function setPos( x:Number, y:Number ):void { this.m_position.setTo( x, y ); this.m_drawPos.setTo( x - this.m_offset.x, y - this.m_offset.y ) ; } }。当您向offset函数提供destPoint时，它是在绘制之前放置copyPixels()左上角的位置。但是，通常情况下，您希望对象具有左上角的不同参考点（例如，圆圈将在其中间具有参考点）。这可以让你处理它。

BitmapData

Answer 2

我知道我现在做错了什么。

这有效;

this.bcg = new BitmapData(800,600,false,0x000000);
canvas.bitmapData.copyPixels(bcg, bcg.rect, new Point(0, 0));

我必须重新声明bcg，然后将其blit到canvas。因为我的rect个对象正在bcg上，所以对吗？我正在创建一个使用的位图;

this.canvas = new Bitmap(bcg);

因此，canvas会引用bcg？

如何在blitting之前清除位图？

2 个答案: