Intense Photo Filter Application

function processImage(originalImg, contrastAmount = 1.5, saturationAmount = 1.5, brightnessAmount = 1.0) {
    // Create a new canvas element
    const canvas = document.createElement('canvas');

    // Set canvas dimensions to the original image's dimensions
    // Use naturalWidth/naturalHeight for the actual dimensions of the image,
    // as .width/.height can be affected by CSS or if the image isn't fully loaded (though it should be).
    canvas.width = originalImg.naturalWidth || originalImg.width;
    canvas.height = originalImg.naturalHeight || originalImg.height;

    // Get the 2D rendering context
    const ctx = canvas.getContext('2d');

    // Validate and prepare filter values
    // Default values from function signature are used if parameters are not provided.
    // If provided parameters are invalid (e.g., non-numeric strings, negative values),
    // fall back to sensible defaults and issue a warning.

    let c = Number(contrastAmount);
    if (isNaN(c) || c < 0) {
        console.warn(`Invalid value for contrastAmount: "${contrastAmount}". Using default 1.5 (150%).`);
        c = 1.5; // Default contrast factor
    }

    let s = Number(saturationAmount);
    if (isNaN(s) || s < 0) {
        console.warn(`Invalid value for saturationAmount: "${saturationAmount}". Using default 1.5 (150%).`);
        s = 1.5; // Default saturation factor
    }

    let b = Number(brightnessAmount);
    if (isNaN(b) || b < 0) {
        console.warn(`Invalid value for brightnessAmount: "${brightnessAmount}". Using default 1.0 (100%).`);
        b = 1.0; // Default brightness factor
    }

    // Construct the filter string for the canvas context
    // Values are multiplied by 100 to convert factors to percentages for CSS filter syntax
    const filters = [];
    filters.push(`contrast(${c * 100}%)`);
    filters.push(`saturate(${s * 100}%)`);
    filters.push(`brightness(${b * 100}%)`);
    
    ctx.filter = filters.join(' ');

    // Draw the original image onto the canvas. The filter will be applied during rendering.
    ctx.drawImage(originalImg, 0, 0, canvas.width, canvas.height);

    // Optional: Reset the filter if the context were to be reused for unfiltered drawings.
    // Not strictly necessary here as we are returning a new canvas with its own context.
    // ctx.filter = 'none'; 

    // Return the canvas element with the filtered image
    return canvas;
}