Scramble filter for use in worker

scramble.ts

export default (
    options: { imageData: ImageData; amount: number },
    done: (err: string, imageData: ImageData) => void
): void => {
    const { imageData, amount = 1 } = options;

    const intensity = Math.round(Math.max(1, amount) * 2);
    const range = Math.round(intensity * 0.5);

    const inputWidth = imageData.width;
    const inputHeight = imageData.height;

    const outputData = new Uint8ClampedArray(inputWidth * inputHeight * 4);
    const inputData = imageData.data;

    let randomData;
    let i = 0,
        x,
        y,
        r;
    let xoffset = 0;
    let yoffset = 0;
    let index;
    const l = inputWidth * inputHeight * 4 - 4;

    for (y = 0; y < inputHeight; y++) {
        randomData = crypto.getRandomValues(new Uint8ClampedArray(inputHeight));

        for (x = 0; x < inputWidth; x++) {
            r = randomData[y] / 255;

            xoffset = 0;
            yoffset = 0;

            if (r < 0.5) {
                xoffset = (-range + Math.round(Math.random() * intensity)) * 4;
            }

            if (r > 0.5) {
                yoffset = (-range + Math.round(Math.random() * intensity)) * (inputWidth * 4);
            }

            // limit to image data
            index = Math.min(Math.max(0, i + xoffset + yoffset), l);

            outputData[i] = inputData[index];
            outputData[i + 1] = inputData[index + 1];
            outputData[i + 2] = inputData[index + 2];
            outputData[i + 3] = inputData[index + 3];

            i += 4;
        }
    }

    done(null, {
        data: outputData,
        width: imageData.width,
        height: imageData.height,
    });
};