Black Sunday Image Generator

function processImage(
    originalImg, 
    contrast = 1.6, 
    brightness = -15, 
    noiseAmount = 30, 
    vignetteStrength = 0.8, 
    text = "Чёрная суббота"
) {
    // Create canvas
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    const width = originalImg.width;
    const height = originalImg.height;
    
    canvas.width = width;
    canvas.height = height;

    // Draw the initial image
    ctx.drawImage(originalImg, 0, 0);

    // Get image data to apply "Black Sunday" / "Чёрная суббота" dark, gritty B&W effect
    const imageData = ctx.getImageData(0, 0, width, height);
    const data = imageData.data;

    const numContrast = Number(contrast);
    const numBrightness = Number(brightness);
    const numNoise = Number(noiseAmount);

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

        // 1. Apply Brightness offset
        r += numBrightness;
        g += numBrightness;
        b += numBrightness;

        // 2. Apply Contrast
        r = numContrast * (r - 128) + 128;
        g = numContrast * (g - 128) + 128;
        b = numContrast * (b - 128) + 128;

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

        // 3. Convert to Grayscale (Luminance formula)
        let gray = 0.299 * r + 0.587 * g + 0.114 * b;

        // 4. Apply Film Grain Noise
        if (numNoise > 0) {
            let noise = (Math.random() - 0.5) * numNoise;
            gray += noise;
            gray = Math.max(0, Math.min(255, gray));
        }

        // Apply updated grayscale value to RGB channels (ignoring alpha channel at i+3)
        data[i] = gray;
        data[i + 1] = gray;
        data[i + 2] = gray;
    }

    // Write the manipulated image data back into the canvas
    ctx.putImageData(imageData, 0, 0);

    // 5. Apply Dark Vignette for a gloomy aesthetic
    const numVignette = Number(vignetteStrength);
    if (numVignette > 0) {
        const gradient = ctx.createRadialGradient(
            width / 2, height / 2, Math.min(width, height) * 0.2, 
            width / 2, height / 2, Math.max(width, height) * 0.7  
        );
        gradient.addColorStop(0, 'rgba(0, 0, 0, 0)');
        gradient.addColorStop(1, `rgba(0, 0, 0, ${numVignette})`);
        
        ctx.fillStyle = gradient;
        ctx.fillRect(0, 0, width, height);
    }

    // 6. Apply the horror/thriller text meme overlay if provided
    if (text) {
        const fontSize = Math.max(20, Math.floor(width * 0.08));
        ctx.font = `bold ${fontSize}px "Courier New", Courier, monospace`;
        ctx.textAlign = "center";
        ctx.textBaseline = "bottom";

        const textX = width / 2;
        const textY = height - Math.max(20, height * 0.05);

        // Heavy dark shadow to separate from background
        ctx.shadowColor = "rgba(0, 0, 0, 0.9)";
        ctx.shadowBlur = Math.max(5, fontSize * 0.3);
        ctx.shadowOffsetX = 3;
        ctx.shadowOffsetY = 3;

        ctx.fillStyle = "#ffffff";
        ctx.fillText(text, textX, textY);
        
        // Secondary subtle dark-red shadow to give it that "Black Sunday" horror vibe
        ctx.shadowColor = "rgba(100, 0, 0, 0.8)";
        ctx.shadowBlur = Math.max(3, fontSize * 0.1);
        ctx.shadowOffsetX = -2;
        ctx.shadowOffsetY = -2;
        ctx.fillText(text, textX, textY);

        // Reset context shadows
        ctx.shadowColor = "transparent";
        ctx.shadowBlur = 0;
        ctx.shadowOffsetX = 0;
        ctx.shadowOffsetY = 0;
    }

    return canvas;
}