Calculate Degrees Of Linear Gradient In Canvas Using Konva With React?

I want to calculate the degree used in a Linear Gradient → linear-gradient(140deg, rgba(165, 142, 251, 1), rgb(233, 191, 248)) into x & y co-ordinates to use it in Konva, whi

Solution 1:

Found the answer on a subreddit for Game Developers /r/gamedev where I shouldn't have asked but I did & it worked.

import { Stage, Layer, Rect } from "react-konva"

// linear-gradient(140deg, rgba(165, 142, 251, 1), rgb(233, 191, 248))
export default function App() {
    const width = window.innerWidth / 1.25 // random width
    const height = window.innerHeight / 1.5 // random height

    // Specify angle in degrees
    const angleInDeg = 140

    // Compute angle in radians - CSS starts from 180 degrees and goes clockwise
    // Math functions start from 0 and go anti-clockwise so we use 180 - angleInDeg to convert between the two
    const angle = ((180 - angleInDeg) / 180) * Math.PI

    // This computes the length such that the start/stop points will be at the corners
    const length =
        Math.abs(width * Math.sin(angle)) + Math.abs(height * Math.cos(angle))

    // Compute the actual x,y points based on the angle, length of the gradient line and the center of the div
    const halfx = (Math.sin(angle) * length) / 2.0
    const halfy = (Math.cos(angle) * length) / 2.0
    const cx = width / 2.0
    const cy = height / 2.0
    const x1 = cx - halfx
    const y1 = cy - halfy
    const x2 = cx + halfx
    const y2 = cy + halfy

    return (
        <div className="App">
            <h1>Linear Gradient in Konva 👇</h1>
            <Stage width={width} height={height}>
                <Layer>
                    <Rect
                        name="transparentBackground"
                        width={width}
                        height={height}
                        x={0}
                        y={0}
                        fillPriority="linear-gradient" // 'color', 'pattern', 'linear-gradient', 'radial-gradient'
                        /* linear-gradient */
                        fillLinearGradientStartPoint={{ x: x1, y: y1 }}
                        fillLinearGradientEndPoint={{ x: x2, y: y2 }}
                        fillLinearGradientColorStops={[
                            0,
                            "rgba(165, 142, 251, 1)",
                            1,
                            "rgb(233, 191, 248)",
                        ]}
                    />
                </Layer>
            </Stage>

            <h1>CSS Gradient 👇</h1>
            <div
                style={{
                    marginTop: 10,
                    width,
                    height,
                    backgroundImage: `linear-gradient(${angleInDeg}deg, rgba(165, 142, 251, 1), rgb(233, 191, 248))`,
                }}
            ></div>
        </div>
    )
}

Codesandbox → https://codesandbox.io/s/linear-gradient-in-react-konva-cpgrk?file=/src/App.tsx