Android圖形映像之以Bitmap作為Canvas畫布的材料

Android圖形映像之以Bitmap作為Canvas畫布的材料
概述

當以Bitmap作為畫布材料時，可以繪製出以下各種圖案：

demo

/** * 圖形影像處理：在Bitmap上繪畫 */public class MyBitMapViewSec extends View {    private int width;    private int height;    private Paint mPaintCircle;    private Paint mPaintRect;    private Bitmap mBitmap;    private Canvas mCanvasBm;    public MyBitMapViewSec(Context context) {        super(context);    }    public MyBitMapViewSec(Context context, AttributeSet attrs) {        super(context, attrs);        mPaintCircle = new Paint();        mPaintCircle.setColor(Color.YELLOW);        mPaintRect = new Paint();        mPaintRect.setColor(Color.GREEN);        //XOR：交疊和被交疊部分均不顯示;DST_OVER：自身交疊部分不顯示；SRC_OVER交疊部分只顯示自己        PorterDuffXfermode mode = new PorterDuffXfermode(PorterDuff.Mode.XOR);        mPaintRect.setXfermode(mode);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);        height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);        setMeasuredDimension(width, height);        //參數：畫布寬、長尺寸和格式        mBitmap = Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_8888);        mCanvasBm = new Canvas(mBitmap);//自訂一個畫布，畫布材料是Bitmap對象    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        canvas.drawColor(Color.RED);        //先在bitmap上畫        mCanvasBm.drawCircle(width / 2, height / 2, width / 2, mPaintCircle);        mCanvasBm.drawRect(0,0,width/2,width/2,mPaintRect);        //將畫好的bitmap畫出來        canvas.drawBitmap(mBitmap,0,0,null);//這一步必不可少    }}

結果示範：
PorterDuffXfermode mode = new PorterDuffXfermode(參數);
參數為PorterDuff.Mode.DST_OVEL時：

參數為PorterDuff.Mode.XOR時：