1、Xfermode分类：

1. AvoidXfermode

不支持硬件加速

2. PixelXorXfermode

不支持硬件加速

3. PorterDuffXfermode

部分支持硬件加速

PorterDuffXfermode模式使用分类：

1、当需要清空图像时：
Mode.CLEAR（清空源图像）
Mode.XOR（清空相交图像）
2、当目标图像和源图像混合，需要生成颜色的叠加特效
Mode.ADD（饱和度相加）
Mode.DARKEN（变暗）
Mode.LIGHTEN（变亮）
Mode.MULTIPLY（正片叠底）
Mode.OVERLAY（叠加）
Mode.SCREEN（滤色）
3、当不需要特效，根据某一张图像的透明像素来裁剪时，由于SRC相关模式与DST相关模式是相通的，唯一不同的是决定当前哪个是目标图像和源图像
Mode.SRC;
Mode.DST;
Mode.SRC_OVER;
Mode.DST_OVER;
Mode.SRC_IN;
Mode.DST_IN;
Mode.SRC_OUT;
Mode.DST_OUT;
Mode.SRC_ATOP;
Mode.DST_ATOP;

1.png 2.png

2、Xfermode使用

public class ProgressView extends View {
    private int mProgress;
    private int dstColor;
    private int srcColor;
    private Paint mPaint;
    private int width = 800;
    private int height = 400;
    private Bitmap dstBmp;
    private Bitmap srcBmp;


    public ProgressView(Context context) {
        this(context,null);
    }

    public ProgressView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs,0);
    }

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


    /**
     * 初始化
     */
    public void init(){
        mPaint = new Paint();
        dstColor= Color.RED;
        srcColor=Color.BLUE;
        dstBmp = makeDst(width,height);
        srcBmp = makeSrc(width,height);
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }


    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        int layerID = canvas.saveLayer(0,0,width,height,mPaint,Canvas.ALL_SAVE_FLAG);

        canvas.drawBitmap(dstBmp, 0, 0, mPaint);
        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        canvas.drawBitmap(srcBmp, 0, mProgress*400/100-400, mPaint);
        mPaint.setXfermode(null);

        canvas.restoreToCount(layerID);

    }

    public Bitmap makeDst(int w, int h) {
        Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(bm);
        Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);

        p.setColor(dstColor);
        c.drawRoundRect(new RectF(0, 0, w, h),200,200, p);
        return bm;
    }

    public Bitmap makeSrc(int w, int h) {
        Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(bm);
        Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);

        p.setColor(srcColor);
        c.drawRect(0, 0,w,h, p);
        return bm;
    }

    public void setProgress(int progress){
        this.mProgress=progress;
        postInvalidate();
    }
}