Developing a transparent "cutout" within a colored container using CSS in React Native (Layout design for a QR code scanner)

I'm currently utilizing react-native-camera for QR scanning, which is functioning properly. However, I want to implement a white screen with opacity above the camera, with a blank square in the middle to indicate where the user should scan the QR code. The challenge arises when trying to position the white screen layout and the blank square so that they are both visible - placing one on top of the other results in visibility issues due to opacity levels.

Is there a way to create a screen with a colored overlay but a cutout in the center?

To give you a clear idea of what I'm aiming for:

https://i.stack.imgur.com/rbwKY.jpg

The area inside the border needs to have 0 opacity.

javascripthtmlcssreactjsreact-native

Answer №1

Create a bold visual effect by applying a large box-shadow to the centered element of your choice.

body {
  display: flex;
  justify-content: center;
  align-items: center;
  background: red;
  height: 100vh;
}

.box {
  width: 50vw;
  height: 50vh;
  border: 2px solid white;
  border-radius: 5vh;
  box-shadow: 0 0 0 2000px rgba(255, 255, 255, .5)
}
<div class="box"></div>

Answer №2

After some trial and error, I was able to find a solution using SVG. This information is here in case others come across the same issue.

To tackle this problem, I utilized react-native-svg to generate the background and a mask for the "Hole":

const styles = StyleSheet.create({
container: {
    position: 'absolute',
    width: deviceWidth,
    height: deviceHeight,
},
layout: {
    position: 'absolute',
    width: deviceWidth,
    height: deviceHeight,
    zIndex: 2,
},
camera: {
    position: 'absolute',
    width: deviceWidth,
    height: deviceHeight,
    zIndex: 1,
}

})

const QrScannerLayout = () => (
<View style={styles.layout}>
    <Svg height="100%" width="100%">
        <Defs>
            <Mask id="mask" x="0" y="0" height="100%" width="100%">
                <Rect height="100%" width="100%" fill='white' opacity={0.8} />
                <Rect
                    x={(deviceWidth / 2) - (QR_SCAN_SQUARE_SIZE / 2)}
                    y={(deviceHeight / 2) - (QR_SCAN_SQUARE_SIZE / 2)}
                    rx='50'
                    ry='50'
                    width={QR_SCAN_SQUARE_SIZE}
                    height={QR_SCAN_SQUARE_SIZE}
                    stroke='white'
                    strokeWidth="5"
                    fill-opacity="0"
                />
            </Mask>
        </Defs>
        <Rect height="100%" width="100%" mask="url(#mask)" fill='white' />
    </Svg>
</View>

);

    render() {
    return (
        <View style={styles.container}>
            <QrScannerLayout />
            <RNCamera
                ref={ref => {
                    this.camera = ref;
                }}
                captureAudio={false}
                onBarCodeRead={this.barcodeRecognized}
                style={styles.camera}
            >
            </RNCamera>
        </View>
    );
}

Answer №3

I have discovered the solution: include this code snippet in your customMarker property

import {Dimensions} from "react-native";

let devicewidth=Dimensions.get("window").width
render() {
    return (
        <View>
            <QRCodeScanner 
                showMarker            
                customMarker={
                    <View style={{flex:1}}>
                        <View style={{flex:1,backgroundColor:"rgba(0,0,0,0.3)"}}/>
                        <View style={{width:devicewidth,
                            height:devicewidth,
                            borderColor:"rgba(0,0,0,0.3)",
                            borderWidth:devicewidth/6,
                        }}>
                            <View style={{flex:1,borderColor:"red",borderWidth:1}}/>
                        </View>
                        <View style={{flex:1,backgroundColor:"rgba(0,0,0,0.3)"}}/>
                    </View>
                }/>
         </View>
     )
}

you can adjust the size of the hole using the borderWidth property(

borderwidth:devicewidth/{how big you want the hole to be}
)

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