问题描述
网上没有资料,特来请教下大神
问题解答
回答1：大致思路：自定义view，先画矩形（drawRect），然后cavas旋转（rotate），再画图片，最后做XOR操作：
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_ATOP));回答2：
可以看看关于PorterDuffXfermode的使用 https://segmentfault.com/a/11...
回答3：Paint.drawPath
参考：多边形ImageView
回答4：使用PorterDuffXfermode, 可以看看图像合成Xfermode和任意形状ImageView
public class RectImageView extends ImageView { private Paint mPaint; private Xfermode mXfermode; private Bitmap mRectMask; public RectImageView(Context context) {this(context, null); } public RectImageView(Context context, AttributeSet attrs) {this(context, attrs, 0); } public RectImageView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mPaint.setColor(Color.RED);// 关键方法mXfermode = new PorterDuffXfermode(PorterDuff.Mode.DST_IN); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);createMask(); } private void createMask() {if (mRectMask == null) { int maskWidth = getMeasuredWidth(); int maskHeight = getMeasuredHeight(); mRectMask = Bitmap.createBitmap(maskWidth, maskHeight, Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(mRectMask); canvas.translate(maskWidth / 2, 0); canvas.rotate(45); int rectSize = (int) (maskWidth / 2 / Math.sin(Math.toRadians(45))); canvas.drawRect(0, 0, rectSize, rectSize, mPaint);} } @Override protected void onDraw(Canvas canvas) {int id = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), null, Canvas.ALL_SAVE_FLAG);super.onDraw(canvas);// 关键方法mPaint.setXfermode(mXfermode);canvas.drawBitmap(mRectMask, 0, 0, mPaint);mPaint.setXfermode(null);canvas.restoreToCount(id); }}
效果如下
