Image Fujifilm GW690 Texas Leica Filter Effect Application

function processImage(originalImg) {
    const canvas = document.createElement('canvas');
    // Use naturalWidth/Height for intrinsic dimensions, fallback to width/height
    const imgWidth = originalImg.naturalWidth || originalImg.width;
    const imgHeight = originalImg.naturalHeight || originalImg.height;

    if (imgWidth === 0 || imgHeight === 0) {
        console.error("Image has zero dimensions. Is it loaded correctly?");
        const errorDiv = document.createElement('div');
        errorDiv.style.color = 'red';
        errorDiv.textContent = 'Error: Image has zero dimensions. Please ensure the image is loaded.';
        return errorDiv;
    }

    canvas.width = imgWidth;
    canvas.height = imgHeight;

    const ctx = canvas.getContext('2d', { willReadFrequently: true }); // willReadFrequently can be an optimization hint
    if (!ctx) {
        console.error("Could not get 2D context from canvas.");
        // Fallback or error element as per guidelines
        const errorDiv = document.createElement('div');
        errorDiv.style.color = 'red';
        errorDiv.textContent = 'Error: Canvas 2D context is not supported or available.';
        return errorDiv;
    }

    try {
        ctx.drawImage(originalImg, 0, 0, canvas.width, canvas.height);
    } catch (e) {
        console.error("Error drawing image to canvas:", e);
        const errorDiv = document.createElement('div');
        errorDiv.style.color = 'red';
        errorDiv.textContent = 'Error: Could not draw the image onto the canvas. The image might be invalid or corrupted.';
        return errorDiv;
    }

    let imageData;
    try {
        imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    } catch (e) {
        // This can happen due to CORS issues if the image is from a different origin
        // and the canvas becomes tainted.
        console.error("Could not get getImageData (possibly CORS issue):", e);
        const errorDiv = document.createElement('div');
        errorDiv.style.color = 'red';
        errorDiv.style.padding = '10px';
        errorDiv.style.border = '1px solid red';
        errorDiv.innerHTML = `<strong>Error processing image:</strong><br>Could not access pixel data.
        If the image is from an external URL, this might be due to Cross-Origin Resource Sharing (CORS) restrictions.
        Try using an image from the same domain or one with appropriate CORS headers.`;
        return errorDiv;
    }
    
    const data = imageData.data;

    // Filter constants for "Fujifilm GW690 Texas Leica" look.
    // This is an artistic interpretation aiming for a filmic look inspired by
    // characteristics of Fujifilm film simulations (e.g., Classic Chrome-like).
    const DESATURATION_AMOUNT = 0.18; // Slight desaturation for an analog feel
    const CONTRAST_FACTOR = 1.22;     // Boost contrast for a punchy, filmic look
    
    // Color multipliers to emulate Fuji color science (e.g., specific green/blue rendering)
    const RED_TWEAK = 1.01;           // Subtle adjustment to reds
    const GREEN_MULTIPLIER = 0.93;    // Mute/shift greens
    const BLUE_MULTIPLIER = 1.07;     // Boost/deepen blues
    
    const GRAIN_STRENGTH = 3;        // Strength of the film grain (noise range)

    for (let i = 0; i < data.length; i += 4) {
        let r = data[i];
        let g = data[i+1];
        let b = data[i+2];

        // 1. Desaturation
        // Apply before contrast to prevent oversaturation of already vivid colors when contrast is increased.
        const gray = 0.299 * r + 0.587 * g + 0.114 * b;
        r = r * (1 - DESATURATION_AMOUNT) + gray * DESATURATION_AMOUNT;
        g = g * (1 - DESATURATION_AMOUNT) + gray * DESATURATION_AMOUNT;
        b = b * (1 - DESATURATION_AMOUNT) + gray * DESATURATION_AMOUNT;

        // 2. Contrast
        // classic contrast formula: factor * (value - midpoint) + midpoint
        r = CONTRAST_FACTOR * (r - 128) + 128;
        g = CONTRAST_FACTOR * (g - 128) + 128;
        b = CONTRAST_FACTOR * (b - 128) + 128;

        // 3. Color Profile Adjustment (Interpretive Fuji-esque Tones)
        r *= RED_TWEAK;
        g *= GREEN_MULTIPLIER;
        b *= BLUE_MULTIPLIER;
        
        // 4. Film Grain (Monochromatic Noise)
        // Adds a subtle texture reminiscent of film.
        if (GRAIN_STRENGTH > 0) {
            const noise = (Math.random() - 0.5) * GRAIN_STRENGTH * 2; 
            r += noise;
            g += noise;
            b += noise;
        }

        // Clamp values to the valid 0-255 range
        data[i]   = Math.max(0, Math.min(255, r));
        data[i+1] = Math.max(0, Math.min(255, g));
        data[i+2] = Math.max(0, Math.min(255, b));
        // Alpha channel (data[i+3]) remains unchanged
    }

    ctx.putImageData(imageData, 0, 0);
    return canvas;
}