Image To 1880s Film Camera Style Converter

function processImage(originalImg, intensity = "1", sepiaTone = "0.8", noiseAmount = "1") {
    // Parse parameters to ensure they are treated as numbers
    intensity = parseFloat(intensity);
    sepiaTone = parseFloat(sepiaTone);
    noiseAmount = parseFloat(noiseAmount);

    // Create the main canvas
    const canvas = document.createElement('canvas');
    const w = originalImg.width;
    const h = originalImg.height;
    canvas.width = w;
    canvas.height = h;
    const ctx = canvas.getContext('2d');

    // 1. Initial 1880s filter application
    // Early film was orthochromatic & slightly soft. We use grayscale -> sepia -> contrast -> blur.
    const blurAmt = 0.8 * intensity;
    const contrast = 105 + (15 * intensity); 
    const sepiaVal = sepiaTone * 100;
    
    // Apply standard canvas filters
    ctx.filter = `grayscale(100%) sepia(${sepiaVal}%) contrast(${contrast}%) brightness(95%) blur(${blurAmt}px)`;
    ctx.drawImage(originalImg, 0, 0, w, h);
    ctx.filter = 'none'; // Reset filters for subsequent drawings

    // 2. Film grain (Noise overlay)
    if (noiseAmount > 0) {
        const noiseCanvas = document.createElement('canvas');
        noiseCanvas.width = 256;
        noiseCanvas.height = 256;
        const nCtx = noiseCanvas.getContext('2d');
        const nData = nCtx.createImageData(256, 256);
        
        for (let i = 0; i < nData.data.length; i += 4) {
            // Emulate silver halide grain
            const val = Math.random() * 255;
            nData.data[i] = val;     // R
            nData.data[i+1] = val;   // G
            nData.data[i+2] = val;   // B
            nData.data[i+3] = Math.random() * 50 * noiseAmount * intensity; // Alpha
        }
        nCtx.putImageData(nData, 0, 0);
        
        ctx.globalCompositeOperation = 'overlay'; 
        ctx.fillStyle = ctx.createPattern(noiseCanvas, 'repeat');
        ctx.fillRect(0, 0, w, h);
        ctx.globalCompositeOperation = 'source-over';
    }

    // 3. Vintage Lens Vignette (Darkened, organic corners)
    const cx = w / 2;
    const cy = h / 2;
    const maxRadius = Math.sqrt(cx * cx + cy * cy);
    
    ctx.globalCompositeOperation = 'multiply';
    const vignette = ctx.createRadialGradient(cx, cy, maxRadius * 0.4, cx, cy, maxRadius * 1.1);
    vignette.addColorStop(0, 'rgba(210, 190, 160, 0)'); // Transparent warm center
    vignette.addColorStop(1, `rgba(40, 20, 5, ${0.85 * intensity})`); // Dark brownish edges simulating old barrel vignette
    ctx.fillStyle = vignette;
    ctx.fillRect(0, 0, w, h);
    ctx.globalCompositeOperation = 'source-over';

    // 4. Physical imperfections (Scratches & dust from old glass plates / film)
    const numScratches = Math.floor(15 * intensity);
    ctx.lineWidth = 1;
    for (let i = 0; i < numScratches; i++) {
        // Vary scratch color between bright and dark
        if (Math.random() > 0.5) {
            ctx.strokeStyle = `rgba(255, 255, 255, ${Math.random() * 0.25 * intensity})`;
        } else {
            ctx.strokeStyle = `rgba(0, 0, 0, ${Math.random() * 0.25 * intensity})`;
        }
        
        ctx.beginPath();
        const sx = Math.random() * w;
        const sy = Math.random() * h;
        const length = Math.random() * h * 0.4;
        const angle = (Math.random() - 0.5) * 0.15; // Scratches tend to be mostly vertical
        ctx.moveTo(sx, sy);
        
        // Slightly wavy line for realistic non-linear scratch
        let cxTemp = sx;
        let cyTemp = sy;
        for(let step = 0; step < 5; step++) {
            cxTemp += Math.sin(angle) * (length / 5) + (Math.random() - 0.5) * 2;
            cyTemp += Math.cos(angle) * (length / 5);
            ctx.lineTo(cxTemp, cyTemp);
        }
        ctx.stroke();
    }

    // Specks of dust and plate emulsion drops
    const numDust = Math.floor(60 * intensity);
    for (let i = 0; i < numDust; i++) {
        ctx.fillStyle = Math.random() > 0.5 
            ? `rgba(0, 0, 0, ${Math.random() * 0.5 * intensity})` 
            : `rgba(255, 255, 255, ${Math.random() * 0.4 * intensity})`;
        
        ctx.beginPath();
        const r = Math.random() * 1.5 + 0.5; // Irregular sizes
        ctx.arc(Math.random() * w, Math.random() * h, r, 0, Math.PI * 2);
        ctx.fill();
    }

    // 5. Final unifying tone wash (helps harmonize scratches and grain into the sepia spectrum)
    ctx.globalCompositeOperation = 'color';
    ctx.fillStyle = `rgba(139, 105, 65, ${0.25 * intensity})`; 
    ctx.fillRect(0, 0, w, h);
    ctx.globalCompositeOperation = 'source-over';

    return canvas;
}