G-Major 5 Image Effect Generator

function processImage(originalImg, mirrorType = "leftToRight", tintColor = "magenta", invertColors = "true", contrastLevel = "1.5") {
    // Determine canvas dimensions from the original image
    const w = originalImg.width;
    const h = originalImg.height;
    
    // Create an off-screen canvas
    const canvas = document.createElement("canvas");
    canvas.width = w;
    canvas.height = h;
    const ctx = canvas.getContext("2d", { willReadFrequently: true });

    // 1. Structural effect: Mirroring (A classic feature of G-Major visual effects)
    if (mirrorType === "leftToRight") {
        // Draw the left half normally
        ctx.drawImage(originalImg, 0, 0, w / 2, h, 0, 0, w / 2, h);
        
        // Setup context to flip horizontally and draw the left half mirrored onto the right
        ctx.save();
        ctx.translate(w, 0);
        ctx.scale(-1, 1);
        ctx.drawImage(originalImg, 0, 0, w / 2, h, 0, 0, w / 2, h);
        ctx.restore();
    } else if (mirrorType === "rightToLeft") {
        // Draw the right half normally
        ctx.drawImage(originalImg, w / 2, 0, w / 2, h, w / 2, 0, w / 2, h);
        
        // Setup context to flip horizontally and draw the right half mirrored onto the left
        ctx.save();
        ctx.translate(w, 0);
        ctx.scale(-1, 1);
        ctx.drawImage(originalImg, w / 2, 0, w / 2, h, w / 2, 0, w / 2, h);
        ctx.restore();
    } else {
        // Draw original layout if no mirror is requested
        ctx.drawImage(originalImg, 0, 0, w, h);
    }

    // 2. Color and Filter effects (Invert, Contrast, and Demonic Tinting)
    const imgData = ctx.getImageData(0, 0, w, h);
    const data = imgData.data;

    const contrast = parseFloat(contrastLevel) || 1.5;
    const doInvert = (invertColors === "true" || invertColors === "1");

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

        // Apply contrast
        r = ((r - 128) * contrast) + 128;
        g = ((g - 128) * contrast) + 128;
        b = ((b - 128) * contrast) + 128;

        // Clamp values to valid 0-255 ranges
        r = Math.max(0, Math.min(255, r));
        g = Math.max(0, Math.min(255, g));
        b = Math.max(0, Math.min(255, b));

        // Apply inversion (Staple of G-Major video effects)
        if (doInvert) {
            r = 255 - r;
            g = 255 - g;
            b = 255 - b;
        }

        // Apply tint overrides to simulate the deep-fried, corrupted look
        if (tintColor === "magenta") {
            r = Math.min(255, r * 1.6);
            g = g * 0.5;
            b = Math.min(255, b * 1.3);
        } else if (tintColor === "red") {
            r = Math.min(255, r * 1.8);
            g = g * 0.4;
            b = b * 0.4;
        } else if (tintColor === "cyan") {
            r = r * 0.4;
            g = Math.min(255, g * 1.6);
            b = Math.min(255, b * 1.6);
        } else if (tintColor === "green") {
            r = r * 0.4;
            g = Math.min(255, g * 1.8);
            b = b * 0.4;
        } else if (tintColor === "blue") {
            r = r * 0.4;
            g = g * 0.4;
            b = Math.min(255, b * 1.8);
        }

        // Reassign the distorted pixels
        data[i] = r;
        data[i + 1] = g;
        data[i + 2] = b;
    }

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

    return canvas;
}