CenterCrop的imageview，水平、垂直方向如果有放大会在该方向移动以居中显示；这里CenterBottomRoundImageView效果如同CenterCrop，并保持水平方向居中能力，但是垂直方向则距底显示。

CenterBottomRoundImageView.java

public class CenterBottomRoundImageView extends RoundCornerImageView {

    private Matrix mMatrix;

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

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

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

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

    private void init() {
        mMatrix = new Matrix();
        super.setScaleType(ScaleType.MATRIX);
    }

    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        updateBounds(this, mMatrix);
    }

    @Override
    public void setImageDrawable(@Nullable Drawable drawable) {
        super.setImageDrawable(drawable);
        updateBounds(this, mMatrix);
    }

    @Override
    public void setImageIcon(@Nullable Icon icon) {
        super.setImageIcon(icon);
        updateBounds(this, mMatrix);
    }

    @Override
    public void setImageURI(@Nullable Uri uri) {
        super.setImageURI(uri);
        updateBounds(this, mMatrix);
    }

    @Override
    public void setImageResource(@DrawableRes int resId) {
        super.setImageResource(resId);
        updateBounds(this, mMatrix);
    }

    @Override
    protected boolean setFrame(int l, int t, int r, int b) {
        final boolean result = super.setFrame(l, t, r, b);
        updateBounds(this, mMatrix);
        return result;
    }

    @Override
    public void setScaleType(ScaleType scaleType) {
    }

    private static void updateBounds(final ImageView iv, @NonNull Matrix matrix) {
        if (iv == null || iv.getDrawable() == null) {
            return;
        }
        final int width = iv.getWidth();
        final int height = iv.getHeight();
        if (width == 0 || height == 0 || iv.getDrawable().getIntrinsicHeight() == 0 || iv.getDrawable().getIntrinsicWidth() == 0) {
            return;
        }
        matrix.reset();
        float scaleWidth = width / (float) iv.getDrawable().getIntrinsicWidth();
        float scaleHeight = height / (float) iv.getDrawable().getIntrinsicHeight();
        float scaleFactor = (scaleWidth > scaleHeight) ? scaleWidth : scaleHeight;
        matrix.setScale(scaleFactor, scaleFactor, 0, 0);
        if (scaleFactor == scaleHeight) {
            float tanslateX = ((iv.getDrawable().getIntrinsicWidth() * scaleFactor) - width) / 2;
            matrix.postTranslate(-tanslateX, 0);
        } else {
            float tanslateY = (iv.getDrawable().getIntrinsicHeight() * scaleFactor) - height;
            matrix.postTranslate(0, -tanslateY);
        }

        iv.setImageMatrix(matrix);
    }
}