Image Singh-Ray Gold-N-Blue Polarizer Effect Tool

function processImage(originalImg) {
    const canvas = document.createElement('canvas');
    const ctx = canvas.getContext('2d');
    canvas.width = originalImg.width;
    canvas.height = originalImg.height;

    // Draw the original image onto the canvas
    ctx.drawImage(originalImg, 0, 0);

    // Get the image data from the canvas
    const imageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
    const data = imageData.data; // This is a Uint8ClampedArray: [R, G, B, A, R, G, B, A, ...]

    // Constants defining the Gold-N-Blue polarizer effect.
    // These values are chosen empirically to approximate the visual characteristics
    // of such a filter.

    // For Blue Enhancement:
    // Factor to boost the blue channel in predominantly blue areas (e.g., sky, water).
    const blueIntensity = 1.3;
    // Factor to reduce the red channel in blue areas, increasing blue purity.
    const bluePurityR = 0.8;
    // Factor to reduce the green channel in blue areas, increasing blue purity.
    const bluePurityG = 0.9;
    // Minimum blue value threshold for a pixel to be considered for strong blue enhancement.
    // This helps target significant blues and avoids over-processing very dark or faint blues.
    const blueDetectionThreshold = 50;

    // For Gold/Warming Effect (applied to non-blue dominant areas):
    // Factor to boost the red channel, creating a golden/warm hue.
    const goldIntensityR = 1.3;
    // Factor to boost the green channel. Kept slightly lower than red's boost
    // to achieve a warmer gold rather than a pure yellow or greenish-yellow.
    const goldIntensityG = 1.1;
    // Factor to reduce the blue channel, enhancing the warmth of the color.
    const goldPurityB = 0.7;

    // Iterate over each pixel (each pixel consists of 4 values: R, G, B, A)
    for (let i = 0; i < data.length; i += 4) {
        let r = data[i];     // Red channel
        let g = data[i+1];   // Green channel
        let b = data[i+2];   // Blue channel
        // Alpha channel (data[i+3]) is preserved.

        let outR, outG, outB;

        // Determine if the pixel is predominantly blue.
        // A pixel is considered "blue dominant" if its blue channel value is greater
        // than both red and green, AND its blue value is above a certain threshold.
        if (b > r && b > g && b > blueDetectionThreshold) {
            // Apply Blue Enhancement
            outB = b * blueIntensity;
            outR = r * bluePurityR;
            outG = g * bluePurityG;
        } else {
            // Apply Gold/Warming Effect to non-blue dominant areas
            // This affects greens, yellows, reds, browns, grays, etc.
            outR = r * goldIntensityR;
            outG = g * goldIntensityG;
            outB = b * goldPurityB;
        }

        // Clamp the resulting R, G, B values to the valid 0-255 range and round them.
        data[i] = Math.max(0, Math.min(255, Math.round(outR)));
        data[i+1] = Math.max(0, Math.min(255, Math.round(outG)));
        data[i+2] = Math.max(0, Math.min(255, Math.round(outB)));
    }

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

    // Return the canvas element
    return canvas;
}