Sunflowered Image Effect Generator

function processImage(originalImg, pointCount = 20000, dotRadius = 3, backgroundColor = "#000000", sizeMode = "brightness") {
    // Determine dimensions
    const width = originalImg.width;
    const height = originalImg.height;

    // Parse parameters
    const points = parseInt(pointCount, 10) || 20000;
    const baseRadius = parseFloat(dotRadius) || 3;
    const mode = String(sizeMode).toLowerCase();

    // Create an off-screen canvas to extract image pixel data
    const srcCanvas = document.createElement('canvas');
    srcCanvas.width = width;
    srcCanvas.height = height;
    const srcCtx = srcCanvas.getContext('2d', { willReadFrequently: true });
    
    // Draw original image on the source canvas
    srcCtx.drawImage(originalImg, 0, 0);
    const imgData = srcCtx.getImageData(0, 0, width, height).data;

    // Create destination canvas for the effect
    const dstCanvas = document.createElement('canvas');
    dstCanvas.width = width;
    dstCanvas.height = height;
    const dstCtx = dstCanvas.getContext('2d');

    // Fill the background
    dstCtx.fillStyle = backgroundColor;
    dstCtx.fillRect(0, 0, width, height);

    // Sunflower mathematical constants (Fermat's Spiral / Golden Ratio)
    const cx = width / 2;
    const cy = height / 2;
    // Max radius needs to reach the corners
    const maxR = Math.sqrt(cx * cx + cy * cy); 
    const c = maxR / Math.sqrt(points);
    const goldenAngle = 137.507764 * (Math.PI / 180);

    // Generate the sunflower seeds arrangement
    for (let i = 1; i <= points; i++) {
        // Calculate polar coordinates
        const angle = i * goldenAngle;
        const r = c * Math.sqrt(i);

        // Convert to cartesian coordinates Let's center it in the middle of canvas
        const x = cx + r * Math.cos(angle);
        const y = cy + r * Math.sin(angle);

        // Only draw if the seed falls within the canvas boundaries
        if (x >= 0 && x < width && y >= 0 && y < height) {
            const px = Math.floor(x);
            const py = Math.floor(y);
            const idx = (py * width + px) * 4;

            // Extract RGBA colors from original image
            const red = imgData[idx];
            const green = imgData[idx + 1];
            const blue = imgData[idx + 2];
            const alpha = imgData[idx + 3] / 255;

            // Determine seed size based on mode
            let drawRadius = baseRadius;
            if (mode === 'brightness') {
                // Calculate perceived luminance
                const luma = (0.299 * red + 0.587 * green + 0.114 * blue) / 255;
                // Scale the dot radius based on brightness (brighter = larger seed)
                drawRadius = baseRadius * (0.2 + 1.2 * luma); 
            }

            // Draw the individual sunflower "seed"
            if (drawRadius > 0 && alpha > 0) {
                dstCtx.beginPath();
                dstCtx.arc(x, y, drawRadius, 0, 2 * Math.PI);
                dstCtx.fillStyle = `rgba(${red}, ${green}, ${blue}, ${alpha})`;
                dstCtx.fill();
            }
        }
    }

    return dstCanvas;
}