Glassed Over - BCACTF 3.0

I created a new way to hide images, see if you can reverse it and find the flag.
    modifiedflag.png
    index.js

index.js

const jimp = require('jimp');

async function main() {
    const image = await jimp.read('flag.png');
    const width = image.bitmap.width;
    const height = image.bitmap.height;
    
    image.scan(0, 0, width, height, (x, y, idx)=>{
        // var red = image.bitmap.data[idx];
        // var green = image.bitmap.data[idx + 1];
        // var blue = image.bitmap.data[idx + 2];
        // var alpha = image.bitmap.data[idx + 3];
        
        image.bitmap.data[idx+3] = Math.random() * 12;
        image.bitmap.data[idx+2] -= 129;
        image.bitmap.data[idx+1] -= 68;

        if (x == image.bitmap.width - 1 && y == image.bitmap.height - 1) {
            image.write("modifiedflag.png");
        }
    });

}
main();

modifiedflag.png

The program uses the jimp library to change some data in flag.png and write it to modifiedflag.png. We can solve this challenge well enough by just flipping some of the signs.

const jimp = require('jimp');

async function main() {
    const image = await jimp.read('modifiedflag.png');
    const width = image.bitmap.width;
    const height = image.bitmap.height;

    image.scan(0, 0, width, height, (x, y, idx)=>{
        image.bitmap.data[idx-3] = Math.random() * 12;
        image.bitmap.data[idx-2] += 129;
        image.bitmap.data[idx-1] += 68;

        if (x == image.bitmap.width - 1 && y == image.bitmap.height - 1) {
            image.write("restoredflag.png");
        }
    });

}
main();

restoredflag.png