圖片塗鴉

public class BAGraffitiView extends View {

    private int panitColor;
    private Bitmap mBitmap;
    private float downX, downY;
    private float tempX, tempY;
    private Bitmap src;
    private List<DrawPath> drawPathList;
    private Paint paint;
    private Path path;
    private Bitmap resultBitmap;

    public BAGraffitiView(Context context) {
        super(context);
    }

    public BAGraffitiView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public BAGraffitiView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    private void init() {
        drawPathList = new ArrayList<>();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mBitmap != null) {
            if (src == null) {
                int width = canvas.getWidth();
                int height = canvas.getHeight();
                int bWidth = mBitmap.getWidth();
                int bHeight = mBitmap.getHeight();
                float wScale = (float) width/bWidth;
                float hScale = (float) height/bHeight;
                Matrix matrix = new Matrix();
                matrix.postScale(wScale, hScale);
                src = Bitmap.createBitmap(mBitmap, 0, 0, bWidth, bHeight, matrix, true);
            }
            canvas.drawBitmap(src, 0, 0, null);
        }
        if (drawPathList != null && drawPathList.size() != 0) {
            for (DrawPath drawPath : drawPathList) {
                canvas.drawPath(drawPath.path, drawPath.paint);
            }
        }
        canvas.save();

    }

    private void initValue() {
        paint = new Paint();
        path = new Path();
        paint.setAntiAlias(true);
        paint.setStrokeWidth(10);
        paint.setStyle(Paint.Style.STROKE);
        if (panitColor == 0) {
            paint.setColor(Color.RED);
        } else {
            paint.setColor(panitColor);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                initValue();
                downX = event.getX();
                downY = event.getY();
                path.moveTo(downX, downY);
                invalidate();
                tempX = downX;
                tempY = downY;
                DrawPath drawPath = new DrawPath();
                drawPath.paint = paint;
                drawPath.path = path;
                drawPathList.add(drawPath);
                break;
            case MotionEvent.ACTION_MOVE:
                float moveX = event.getX();
                float moveY = event.getY();
                path.quadTo(tempX, tempY, moveX, moveY);
                invalidate();
                tempX = moveX;
                tempY = moveY;
                break;
        }
        return true;
    }

    //設置顏色
    public void setPanitColor(int panitColor) {
        this.panitColor = panitColor;
    }

    //設置背景圖片
    public void setmBitmap(Bitmap mBitmap) {
        this.mBitmap = mBitmap;
    }

    //撤銷
    public void undo() {
        if (drawPathList.size() > 0) {
            drawPathList.remove(drawPathList.size() - 1);
            invalidate();
        }
    }

    public Bitmap getSrc() {
        return this.src;
    }

    class DrawPath {
        Paint paint;
        Path path;
    }
}