Photo Night To Day Converter

function processImage(originalImg, exposure = 1.8, gamma = 1.4, saturation = 1.3, blueBoost = 10) {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    
    // Set canvas dimensions to match the original image
    canvas.width = originalImg.width;
    canvas.height = originalImg.height;
    
    // Draw the original image onto the canvas
    ctx.drawImage(originalImg, 0, 0);
    
    // Get the image data to manipulate pixels
    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data;
    
    // Ensure parameters are numbers
    const exp = parseFloat(exposure);
    const gam = parseFloat(gamma);
    const sat = parseFloat(saturation);
    const bBoost = parseFloat(blueBoost);

    // Process each pixel
    for (let i = 0; i < data.length; i += 4) {
        let r = data[i];
        let g = data[i + 1];
        let b = data[i + 2];
        
        // 1. Exposure: Multiply pixels to brighten up the extremely dark night areas
        r *= exp;
        g *= exp;
        b *= exp;
        
        // 2. Gamma Correction: Lightens midtones and shadows more than highlights to prevent total blowout
        r = 255 * Math.pow(r / 255, 1 / gam);
        g = 255 * Math.pow(g / 255, 1 / gam);
        b = 255 * Math.pow(b / 255, 1 / gam);
        
        // 3. Color Balance / Blue Boost: Day scenes typically have more blue (sky ambient light)
        // Night photos often skew yellow/orange (street lights) or grey
        b += bBoost;
        
        // 4. Saturation: Brightening a dark image washes out colors, so we restore/boost them
        // Calculate relative luminance
        const lum = 0.299 * r + 0.587 * g + 0.114 * b;
        
        // Interpolate between luminance (grayscale) and the original color based on saturation factor
        r = lum + sat * (r - lum);
        g = lum + sat * (g - lum);
        b = lum + sat * (b - lum);
        
        // Clamp the RGB values between 0 and 255
        data[i]     = Math.min(255, Math.max(0, r));
        data[i + 1] = Math.min(255, Math.max(0, g));
        data[i + 2] = Math.min(255, Math.max(0, b));
        // data[i + 3] is alpha, which we leave untouched
    }
    
    // Put the processed image data back onto the canvas
    ctx.putImageData(imageData, 0, 0);
    
    return canvas;
}