Photo Golden Hour Mood Filter

function processImage(originalImg, intensity = 0.7, targetRedMultiplier = 1.2, targetGreenMultiplier = 1.1, targetBlueMultiplier = 0.85) {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d', { willReadFrequently: true }); // willReadFrequently for performance if getImageData is used often

    // Ensure the image is loaded and has dimensions
    const imgWidth = originalImg.naturalWidth || originalImg.width;
    const imgHeight = originalImg.naturalHeight || originalImg.height;

    if (!imgWidth || !imgHeight) {
        console.error("Image is not loaded or has no dimensions.");
        // Return an empty canvas or throw an error, depending on desired behavior
        canvas.width = 0;
        canvas.height = 0;
        return canvas;
    }

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

    // Draw the original image onto the canvas
    ctx.drawImage(originalImg, 0, 0, canvas.width, canvas.height);

    // If intensity is 0, no filter is applied, return the canvas with the original image
    if (intensity === 0) {
        return canvas;
    }

    // Get the image data from the canvas
    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data; // This is a Uint8ClampedArray: [R,G,B,A, R,G,B,A, ...]

    // Calculate the effective multipliers based on the intensity
    // This uses linear interpolation: final_value = (1-intensity)*initial_value + intensity*target_value
    // For multipliers, the initial_value (no effect) is 1.0.
    const actualRedMultiplier = 1 * (1 - intensity) + targetRedMultiplier * intensity;
    const actualGreenMultiplier = 1 * (1 - intensity) + targetGreenMultiplier * intensity;
    const actualBlueMultiplier = 1 * (1 - intensity) + targetBlueMultiplier * intensity;

    // Iterate through each pixel (4 values at a time: R, G, B, A)
    for (let i = 0; i < data.length; i += 4) {
        const r = data[i];   // Red channel
        const g = data[i+1]; // Green channel
        const b = data[i+2]; // Blue channel
        // Alpha channel (data[i+3]) is left unchanged

        // Apply the multipliers
        let newR = r * actualRedMultiplier;
        let newG = g * actualGreenMultiplier;
        let newB = b * actualBlueMultiplier;

        // The Uint8ClampedArray automatically clamps values to the 0-255 range.
        // So, explicit Math.min(255, ...) or Math.max(0, ...) is not strictly necessary here,
        // but can be kept for clarity if preferred.
        // For this implementation, we will rely on the clamping behavior of Uint8ClampedArray.
        data[i]   = newR;
        data[i+1] = newG;
        data[i+2] = newB;
    }

    // Put the modified image data back onto the canvas
    ctx.putImageData(imageData, 0, 0);

    return canvas;
}