Draw lines and polygons with canvas. Save and load path to canvas.


Keywords
react, canvas, draw, polygons, polygon, line, lines
License
MIT
Install
npm install react-canvas-polygons@1.1.18

Documentation

React Canvas Polygons

It is a react component that helps you draw line rectangles and any polygon with canvas on top of images.

Everything that you draw is stored in a state. You can access this state through the property onCompleteDraw.

This component was designed to draw fences which are used by computer vision application in the back end.

The points saved are relative to the canvas size. It follows the browser coordinate system (0, 0) on the top left.

Warning: On version 1.1.10 there is a breaking change. The onCompleteDraw was renamed to onDataUpdate and

a new callback function was added onFinishDraw.

Installation

npm i -E react-canvas-polygons

Component Props

Prop Type Default Req  Description
brushSize Number 2 - BrushSize to draw
canUndo Boolean false - CanUndo
color String '#000000' - Color of what we want draw
height Number 300 - the height of the canvas
imgSrc String - Background image to canvas;
initialData Object - Is the data to be be draw when load the component
onCompleteDraw Function - This is a callback function that we be called everytime a shape finish to draw
tool Enum('Line','Polygon','Rectangle') 'Line' - Shapes that you can select to draw
width Number 300 - The width of canvas

Usage Example

import React, { Suspense } from 'react';
import type from 'prop-types';
import { CircularProgress } from '@material-ui/core';
import Canvas from 'react-canvas-polygons';

class DrawCanvas extends React.PureComponent {

    handleCleanCanva = () => this.canva.cleanCanvas();

    render() {
        const { imageInfo, tool, onCompleteDraw, fenceData } = this.props;
        const imageInfoLength = Object.keys(imageInfo).length === 0;

        return(
            <Suspense fallback={<CircularProgress color="secondary" />}>
                <button variant="outlined" style={{ marginBottom: '20px' }}
                    onClick={this.handleCleanCanva}
                >
                    Clean Canvas
                </button>
                {imageInfoLength &&
                    <CircularProgress color="secondary" />
                }
                <Canvas
                    ref={canva => this.canva = canva}
                    imgSrc={imageInfo.url}
                    height={imageInfo.height}
                    width={imageInfo.width}
                    tool={tool}
                    onCompleteDraw={onCompleteDraw}
                    initialData={fenceData}
                />
            </Suspense>
        );
    }
}

export default DrawCanvas;

DrawCanvas.propTypes = {
    tool: type.string,
    imageInfo: type.object,
};

Cleaning the canvas

Use a reference to the object and call cleanCanvas() method like demonstrate in the example above

    handleCleanCanva = () => this.canva.cleanCanvas();

This will clean the canvas and reset the component state.

Exampe of State Saved

{
    "Line": [
        [
            [
                39,
                46
            ],
            [
                28,
                181
            ]
        ]
    ],
    "Rectangle": [
        [
            [
                207,
                152
            ],
            [
                268,
                215
            ]
        ]
    ],
    "Polygon_CBC39F42": [
        [
            113,
            52
        ],
        [
            65,
            136
        ],
        [
            101,
            167
        ],
        [
            158,
            141
        ],
        [
            100,
            90
        ]
    ],
    "Polygon_CBC39F44": [
        [
            113,
            52
        ],
        [
            65,
            136
        ],
        [
            101,
            167
        ],
        [
            158,
            141
        ],
        [
            167,
            69
        ]
    ]
}