Question

我一直在寻找有关如何使用react native在图像中绘制矩形的参考，但是我什么也没找到。

我想做的是像传递参数，照片和矩形对角线的顶点坐标作为参数，然后返回带有该绘制矩形的图像。我该怎么办？

Answer 1

想简单..就像用背景色创建div一样。这是示例：

import * as React from 'react';
import { Text, View, StyleSheet, Image } from 'react-native';
import { Constants } from 'expo';

export default class App extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <View style={styles.rectangle}></View>
        <Image source={require('assets/snack-icon.png')} />
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    paddingTop: Constants.statusBarHeight,
    backgroundColor: '#ecf0f1',
    padding: 8,
    position: 'relative',
  },
  rectangle: {
    height: 128,
    width: 128,
    backgroundColor: 'salmon',
    position: 'absolute', 
    zIndex: 99,
    top: '50%',
    left: '40%'
  },

});

结果：

Answer 2

创建一个以Image和View（Rectangle box）作为子视图的视图。通过将绝对位置设置为矩形将Image上的矩形框放置在Image上。要定位，必须设置上，下，左和右的矩形样式值。已经创建了一个传递位置值的函数。

检查此示例：

import * as React from "react";
import { Text, View, StyleSheet, Image } from "react-native";

export default class App extends React.Component {
  renderImage = (topPosition, bottomPosition, leftPosition, rightPosition) => {
    return (
      <View style={styles.imageContainer}>
        <Image
          source={{
            uri:
              "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRzwZW9gvrxF2McRF-wP5TxCIBU_3fA2XDl9DESsm1uqowjSvZ1"
          }}
          style={styles.image}
          resizeMode="stretch"
        />
        <View
          style={[
            styles.rectangle,
            {
              top: topPosition,
              bottom: bottomPosition,
              left: leftPosition,
              right: rightPosition
            }
          ]}
        />
      </View>
    );
  };

  render() {
    return (
      <View style={styles.container}>{this.renderImage(80, 55, 30, 70)}</View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: "center",
    backgroundColor: "#ecf0f1",
    padding: 8
  },
  imageContainer: {
    width: 300,
    height: 250,
    alignSelf: "center"
  },
  image: {
    width: 300,
    height: 250
  },
  rectangle: {
    borderWidth: 3,
    borderColor: "red",
    position: "absolute"
  }
});

如何在React Native中在图像中绘制矩形

2 个答案: