20190110

看看这本书 -《Android游戏编程之从零开始》

Day_3 2019/01/21

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Bitmap 位图的渲染与操作

首先，最简单的如何生成一张位图，如下

Bitmap bitmap = BitmapFactory.decodeResource( this.getResources() , R.mipmap.ic_launcher );

下面是常用的操作函数

public class BitmapSurfaceView extends SurfaceView implements SurfaceHolder.Callback
{
    private SurfaceHolder holder;
    private Canvas canvas;
    private Bitmap bitmap = BitmapFactory.decodeResource( this.getResources() , R.mipmap.ic_launcher );
    private Paint paint;
    
    public BitmapSurfaceView( Context context )
    {
        super( context );
        holder = this.getHolder();
        holder.addCallback( this );
        setFocusable( true );
        paint = new Paint();
        paint.setColor( Color.BLACK );
    }
    
    @Override
    public void surfaceCreated( SurfaceHolder surfaceHolder )
    {
        myDraw();
    }
    
    private void myDraw()
    {
        try
        {
            canvas = holder.lockCanvas();
            if( canvas != null )
            {
                //用于保存当前画布的状态
                canvas.save();
                //旋转方式1
                canvas.rotate( 30 , bitmap.getWidth() / 2 , bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                //用于恢复上次保存的画布状态
                canvas.restore();
                canvas.drawBitmap( bitmap , 100 , 0 , paint );
                //旋转方式2
                Matrix mx = new Matrix();
                mx.postRotate( 30 , bitmap.getWidth() / 2 , bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , mx , paint );
                //平移位图方式1
                canvas.save();
                //平移距离可小于0，表示往左移动
                canvas.translate( 10 , 10 );
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                canvas.restore();
                //平移位图方式2
                Matrix matrix = new Matrix();
                matrix.postTranslate( 10 , 10 );
                canvas.drawBitmap( bitmap , matrix , paint );
                //缩放位图
                canvas.save();
                //============x轴缩放比例===y轴的===========x轴起始点==========================y轴起始点
                canvas.scale( 2f , 2f , 50 + bitmap.getWidth() / 2 , 50 + bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , 50 , 50 , paint );
                canvas.restore();
                canvas.drawBitmap( bitmap , 50 , 50 , paint );
                //x轴镜像
                canvas.save();
                canvas.scale( -1 , 1 , bitmap.getWidth() / 2 , bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                canvas.restore();
                //y轴镜像
                canvas.save();
                canvas.scale( 1 , -1 , bitmap.getWidth() / 2 , bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                canvas.restore();
                //x轴镜像
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                Matrix matrix1 = new Matrix();
                //使用矩阵的移动方法
                matrix.postTranslate( 100 , 100 );
                matrix.postScale( -1 , 1 , 100 + bitmap.getWidth() / 2 , 100 + bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , matrix1 , paint );
                //y轴镜像
                canvas.drawBitmap( bitmap , 0 , 0 , paint );
                Matrix matrix2 = new Matrix();
                //使用矩阵的移动方法
                matrix2.postTranslate( 100 , 100 );
                matrix2.postScale( 1 , -1 , 100 + bitmap.getWidth() / 2 , 100 + bitmap.getHeight() / 2 );
                canvas.drawBitmap( bitmap , matrix2 , paint );
            }
        }
        catch( Exception e )
        {
            e.printStackTrace();
        }
        finally
        {
            if( canvas != null )
            {
                holder.unlockCanvasAndPost( canvas );
            }
        }
    }
    
    @Override
    public void surfaceChanged(
            SurfaceHolder surfaceHolder ,
            int i ,
            int i1 ,
            int i2 )
    {
    
    }
    
    @Override
    public void surfaceDestroyed( SurfaceHolder surfaceHolder )
    {
    
    }
}