Image Kodak Vision3 250D Motion Picture Film Effect Filter

function processImage(originalImg, intensity = 1.0) {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d', { willReadFrequently: true });

    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;

    // Clamp intensity to the range [0, 1]
    const effectIntensity = Math.max(0, Math.min(1, parseFloat(String(intensity)) || 1.0));

    // Parameters for Kodak Vision3 250D effect emulation (full intensity values)
    const saturationAdjust = 1.05; 
    const contrastGamma = 0.97;    
    const blackLift = 0.02;        
    const highlightCompressionThreshold = 0.85; 
    const highlightCompressionFactor = 0.75;  

    // Helper function to process tone curve for a single channel (normalized value 0-1)
    function processChannelTone(value) {
        // a. Lift blacks
        value = blackLift + (1.0 - blackLift) * value;
        
        // b. Mid-tone contrast (using gamma); gamma < 1 brightens mid-tones/shadows relative to highlights
        value = Math.pow(value, contrastGamma);
        
        // c. Highlight compression (rolloff)
        if (value > highlightCompressionThreshold) {
             value = highlightCompressionThreshold + (value - highlightCompressionThreshold) * highlightCompressionFactor;
        }
        return value;
    }

    for (let i = 0; i < data.length; i += 4) {
        const r_orig = data[i];
        const g_orig = data[i+1];
        const b_orig = data[i+2];

        let r = r_orig;
        let g = g_orig;
        let b = b_orig;

        // Apply effects only if intensity > 0
        if (effectIntensity > 0) {
            // 1. Kodak-like Color Matrix Transformation
            // Coefficients are chosen to emulate a typical warm, rich Kodak film look.
            // Vision3 250D is known for natural colors, so shifts are subtle.
            let r_transformed = r * 1.01 + g * 0.02 - b * 0.03;
            let g_transformed = r * -0.01 + g * 0.99 + b * 0.02;
            let b_transformed = r * 0.02 - g * 0.03 + b * 0.96;
            
            r = r_transformed;
            g = g_transformed;
            b = b_transformed;

            // 2. Tone Curve Adjustments (Normalized space)
            let r_n = processChannelTone(r / 255.0);
            let g_n = processChannelTone(g / 255.0);
            let b_n = processChannelTone(b / 255.0);
            
            r = r_n * 255;
            g = g_n * 255;
            b = b_n * 255;

            // 3. Saturation Adjustment
            if (saturationAdjust !== 1.0) { // Avoid processing if no change
                const lum = 0.299 * r + 0.587 * g + 0.114 * b; // Calculate luminance
                r = lum + saturationAdjust * (r - lum);
                g = lum + saturationAdjust * (g - lum);
                b = lum + saturationAdjust * (b - lum);
            }

            // Interpolate between original and filtered based on intensity
            r = r_orig * (1 - effectIntensity) + r * effectIntensity;
            g = g_orig * (1 - effectIntensity) + g * effectIntensity;
            b = b_orig * (1 - effectIntensity) + b * effectIntensity;
        }

        // 4. Clamping to 0-255 range
        data[i]   = Math.max(0, Math.min(255, r));
        data[i+1] = Math.max(0, Math.min(255, g));
        data[i+2] = Math.max(0, Math.min(255, b));
        // Alpha channel (data[i+3]) remains unchanged
    }

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