Lucky Image Effect Generator

function processImage(originalImg, intensity = 50, sparklesCount = 45, theme = "gold", seed = 1337) {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    const width = originalImg.width;
    const height = originalImg.height;

    canvas.width = width;
    canvas.height = height;

    // Apply color boost to make the image jump out (Lucky charm card effect)
    const valSaturate = 100 + Number(intensity);
    const valContrast = 100 + (Number(intensity) / 2);
    ctx.filter = `saturate(${valSaturate}%) contrast(${valContrast}%)`;
    ctx.drawImage(originalImg, 0, 0, width, height);
    ctx.filter = 'none';

    // Simple Pseudo-Random Number Generator for consistent "luck" based on seed
    let currentSeed = Number(seed);
    const random = () => {
        let x = Math.sin(currentSeed++) * 10000;
        return x - Math.floor(x);
    };

    // 1. Add "Shiny Foil" overlay
    ctx.globalCompositeOperation = 'overlay';
    const grad = ctx.createLinearGradient(0, 0, width, height);
    
    const selectedTheme = String(theme).toLowerCase();
    if (selectedTheme === 'rainbow') {
        grad.addColorStop(0, '#ff2a2a');
        grad.addColorStop(0.16, '#ff7a2a');
        grad.addColorStop(0.33, '#e8ff2a');
        grad.addColorStop(0.5, '#2aff30');
        grad.addColorStop(0.66, '#2a30ff');
        grad.addColorStop(0.83, '#c22aff');
        grad.addColorStop(1, '#ff2a2a');
    } else if (selectedTheme === 'emerald') {
        grad.addColorStop(0, '#00ff87');
        grad.addColorStop(0.5, '#60efff');
        grad.addColorStop(1, '#00ff87');
    } else {
        // Gold / Default theme
        grad.addColorStop(0, '#bf953f');
        grad.addColorStop(0.25, '#fcf6ba');
        grad.addColorStop(0.5, '#b38728');
        grad.addColorStop(0.75, '#fbf5b7');
        grad.addColorStop(1, '#aa771c');
    }

    // Apply foil with variable intensity opacity
    ctx.globalAlpha = (Number(intensity) / 100) * 0.7 + 0.1;
    ctx.fillStyle = grad;
    ctx.fillRect(0, 0, width, height);

    // 2. Add sparkles
    ctx.globalCompositeOperation = 'screen';
    const maxDim = Math.max(width, height);
    
    for (let i = 0; i < Number(sparklesCount); i++) {
        const x = random() * width;
        const y = random() * height;
        const size = (random() * 0.05 + 0.01) * maxDim; // Sparkles dynamically scaled to image size
        const opacity = random() * 0.6 + 0.4;

        ctx.save();
        ctx.translate(x, y);
        ctx.globalAlpha = opacity;
        
        // Draw dramatic star shape for the sparkle
        ctx.beginPath();
        ctx.moveTo(0, -size);
        ctx.quadraticCurveTo(0, 0, size, 0);
        ctx.quadraticCurveTo(0, 0, 0, size);
        ctx.quadraticCurveTo(0, 0, -size, 0);
        ctx.quadraticCurveTo(0, 0, 0, -size);
        ctx.closePath();
        
        // Sparkle coloring based on theme
        const starGrad = ctx.createRadialGradient(0, 0, 0, 0, 0, size);
        starGrad.addColorStop(0, 'rgba(255, 255, 255, 1)');
        
        if (selectedTheme === 'gold') {
            starGrad.addColorStop(0.2, 'rgba(255, 220, 100, 0.8)');
            starGrad.addColorStop(1, 'rgba(255, 200, 0, 0)');
        } else if (selectedTheme === 'emerald') {
            starGrad.addColorStop(0.2, 'rgba(100, 255, 150, 0.8)');
            starGrad.addColorStop(1, 'rgba(0, 255, 100, 0)');
        } else {
            // Rainbow / Silver
            starGrad.addColorStop(0.2, 'rgba(220, 220, 255, 0.8)');
            starGrad.addColorStop(1, 'rgba(100, 150, 255, 0)');
        }
        
        ctx.fillStyle = starGrad;
        ctx.fill();

        // Add an extra thin bright flare
        ctx.rotate(random() * Math.PI);
        ctx.beginPath();
        ctx.ellipse(0, 0, size * 1.5, size * 0.05, 0, 0, Math.PI * 2);
        ctx.fillStyle = 'rgba(255, 255, 255, 0.6)';
        ctx.fill();

        ctx.restore();
    }

    // 3. Add soft dark vignette to enhance focus on the center
    ctx.globalCompositeOperation = 'multiply';
    ctx.globalAlpha = 1.0;
    const vigGrad = ctx.createRadialGradient(width/2, height/2, maxDim * 0.3, width/2, height/2, maxDim);
    vigGrad.addColorStop(0, 'rgba(0, 0, 0, 0)');
    vigGrad.addColorStop(1, 'rgba(0, 0, 0, 0.4)');
    ctx.fillStyle = vigGrad;
    ctx.fillRect(0, 0, width, height);

    return canvas;
}