How to mask / crop a rectangle in ImageView

Question

I created a custom ImageViewone to create a transparent rectangle inside the image to make the ImageView visible behind it. However, I can’t understand. I looked through many other answers, and this is what I came up with:

public class MaskImageView extends ImageView {
    private Paint maskPaint;

    public MaskImageView(Context context) {
        super(context);
        init();
    }

    public MaskImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public MaskImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public MaskImageView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init();
    }

    public void init() {
        maskPaint = new Paint();
        maskPaint.setColor(Color.TRANSPARENT);
        maskPaint.setAntiAlias(true);
        maskPaint.setStyle(Paint.Style.FILL);
        maskPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawRect(100, 400, 900, 900, maskPaint);
    }

    public void setMaskWidth(int width) {
        maskWidth = width;
    }
}

And this is the XML layout:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/holo_red_dark"
        android:scaleType="centerCrop"
        android:src="@drawable/blackwhite" />


    <io.example.test.MaskImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/holo_red_dark"
        android:scaleType="centerCrop"
        android:src="@drawable/color" />
</RelativeLayout>

I get the photo on the left, but I want it to look like the photo on the right. Note that regular ImageViewdrawable is a black and white version of a photograph MaskImageView.

Answer 1

View, ImageView, , . , , , Rect, , , .

:

public class MaskImageView extends ImageView
{
    private Rect mMaskRect;

    public MaskImageView(Context context)
    {
        super(context);
        init();
    }

    public MaskImageView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        init();
    }

    public MaskImageView(Context context, AttributeSet attrs, int defStyleAttr)
    {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init()
    {
        mMaskRect = new Rect();    
    }

    // Use this to define the area which should be masked. 
    public void setRect(Rect rect)
    {
        mMaskRect.set(rect);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        canvas.clipRect(mMaskRect, Region.Op.DIFFERENCE);
        super.onDraw(canvas);
    }
}

, , , . .

Answer 2

, .. ImageView ImageView. , ImageView.

, ImageView, , , :

fooobar.com/questions/26543/...

, :

fooobar.com/questions/223817/...