Using GlobalCompositeOperation To Mask Group Of Shapes, In React Konva

My project uses React Konva (https://github.com/konvajs/react-konva) I am trying to draw multiple shapes into a Group and use this to mask the image 'below'. When my component draw

Solution 1:

Ah, just found the solution.

It seems that the entire Group needs to be cached before the globalCompositeOperation is applied. I am assuming this means that the Group gets flattened/rasterised first.

In my React component, I achieved the solution as follows:

 import React from 'react';
import { Image, Group, Rect } from 'react-konva';

class CutoutImage extends React.Component {
    state = {
        image: null,
        mask: null
    }

    componentDidMount() {
        const image = new window.Image();
        image.src = "/images/frisbee.jpg";
        image.onload = () => {
            this.setState({ image });
        }
    }

    componentDidUpdate() {
        if (this.image) {
            this.image.cache();
        }
        if (this.mask) {
            this.mask.cache();
        }
    }

    render() {
        return (

            <Group>
                <Image 
                    image={this.state.image} 
                    ref={node => { this.image = node; }} 
                />
                <Group 
                    globalCompositeOperation={"destination-in"} 
                    ref={node => {this.mask = node; }}
                    >
                    <Rect fill={"#555555"} 
                        width={200} height={200} 
                        x={100} y={100} 
                    />
                    <Rect fill={"#dddddd"} 
                        width={200} height={200} 
                        x={300} y={300} 
                    />
                    <Rect fill={"#dddddd"} 
                        width={200} height={100} 
                        x={150} y={350} 
                    />
                </Group>
            </Group>
        )

    }

}
export default CutoutImage;

And the result: