Image Amethyst Crystal Filter Effect Tool

async function processImage(originalImg, intensityStr = "0.6", rTintStr = "150", gTintStr = "80", bTintStr = "200", contrastStr = "1.1") {
    // Parse parameters and set defaults if parsing fails
    let intensity = parseFloat(intensityStr);
    if (isNaN(intensity)) intensity = 0.6;

    let rTint = parseInt(rTintStr, 10);
    if (isNaN(rTint)) rTint = 150;

    let gTint = parseInt(gTintStr, 10);
    if (isNaN(gTint)) gTint = 80;

    let bTint = parseInt(bTintStr, 10);
    if (isNaN(bTint)) bTint = 200;

    let contrast = parseFloat(contrastStr);
    if (isNaN(contrast)) contrast = 1.1;

    // Ensure the image is loaded before processing
    if (!originalImg.complete || originalImg.naturalWidth === 0) {
        // If the image is not loaded, wait for it to load
        await new Promise((resolve, reject) => {
            originalImg.onload = resolve;
            originalImg.onerror = (err) => {
                console.error("Error loading image:", err);
                reject(err); // Reject the promise if image loading fails
            };
            // If src is not set or loading has not started, reject (or handle as per requirement)
            // For this case, we assume src is set and it's trying to load or already loaded.
        });
    }
    
    if (originalImg.naturalWidth === 0 || originalImg.naturalHeight === 0) {
        console.error("Image has zero dimensions an_img.onload completed.");
        // Create a small empty canvas as a fallback or throw error
        const errorCanvas = document.createElement('canvas');
        errorCanvas.width = 1;
        errorCanvas.height = 1;
        return errorCanvas;
    }


    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');

    canvas.width = originalImg.naturalWidth;
    canvas.height = originalImg.naturalHeight;

    ctx.drawImage(originalImg, 0, 0);

    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data;

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

        // Apply Amethyst Tint using linear interpolation
        let tintedR = r * (1 - intensity) + rTint * intensity;
        let tintedG = g * (1 - intensity) + gTint * intensity;
        let tintedB = b * (1 - intensity) + bTint * intensity;

        // Apply Contrast Boost
        // The contrast factor adjusts how much colors deviate from the midpoint (0.5 or 127.5)
        // A contrast of 1.0 means no change.
        if (contrast !== 1.0) {
            // Normalize to 0-1 range
            let normR = tintedR / 255.0;
            let normG = tintedG / 255.0;
            let normB = tintedB / 255.0;

            // Apply contrast: (value - 0.5) * factor + 0.5
            normR = (normR - 0.5) * contrast + 0.5;
            normG = (normG - 0.5) * contrast + 0.5;
            normB = (normB - 0.5) * contrast + 0.5;

            // Convert back to 0-255 range
            tintedR = normR * 255.0;
            tintedG = normG * 255.0;
            tintedB = normB * 255.0;
        }
        
        // Clamp values to the 0-255 range
        data[i]   = Math.max(0, Math.min(255, tintedR));
        data[i+1] = Math.max(0, Math.min(255, tintedG));
        data[i+2] = Math.max(0, Math.min(255, tintedB));
        // Alpha channel (data[i+3]) remains unchanged
    }

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