public class CanvasExtenderSimpleFilter extends GenericRasterFilter {

    static Logger logger = LoggerFactory.getLogger(CanvasExtenderSimpleFilter.class);

    @Override
    public BufferedImage doFilter(@NotNull BufferedImage src, @Nullable Map<String, Object> parameters) {
        int bs = (Integer) parameters.get("borderSize");
        checkArgument(bs > 0);
        int x = src.getWidth();
        int y = src.getHeight();
        logger.trace(":: detect input image size : {} x {} and colorModel = {}",x, y, src.getColorModel());
        int xr = x + 2 * bs;
        int yr = y + 2 * bs;
        BufferedImage dest = new BufferedImage(xr, yr, BufferedImage.TYPE_INT_ARGB);
        Raster.copyImageIntoPos(src, dest, bs, bs);
        // Left
        for (int j = bs; j > 0; j--) {
            for (int i = 1; i < yr - 1; i++) {
                int pixel1 = dest.getRGB(j, i - 1);
                int pixel2 = dest.getRGB(j, i);
                int pixel3 = dest.getRGB(j, i + 1);
                int res = Raster.avgPixel(pixel1, pixel2, pixel3);
                dest.setRGB(j - 1, i, res);
            }
        }

        // Right
        for (int j = bs + x - 1; j < xr - 1; j++) {
            for (int i = 1; i < yr - 1; i++) {
                int pixel1 = dest.getRGB(j, i - 1);
                int pixel2 = dest.getRGB(j, i);
                int pixel3 = dest.getRGB(j, i + 1);
                int res = Raster.avgPixel(pixel1, pixel2, pixel3);
                dest.setRGB(j + 1, i, res);
            }
        }

        // Top
        for (int i = bs; i > 0; i--) {
            for (int j = 1; j < xr - 1; j++) {
                int pixel1 = dest.getRGB(j - 1, i);
                int pixel2 = dest.getRGB(j,     i);
                int pixel3 = dest.getRGB(j + 1, i);
                int res = Raster.avgPixel(pixel1, pixel2, pixel3);
                dest.setRGB(j, i - 1, res);
            }
        }

        // Bottom
        for (int i = y + bs; i < yr; i++) {
            for (int j = 1; j < xr - 1; j++) {
                int pixel1 = dest.getRGB(j - 1, i - 1);
                int pixel2 = dest.getRGB(j,     i - 1);
                int pixel3 = dest.getRGB(j + 1, i - 1);
                int res = Raster.avgPixel(pixel1, pixel2, pixel3);
                dest.setRGB(j, i, res);
            }
        }


        // TODO: Implement all border directions
        return dest;
    }

}

public static void copyImageIntoPos(@NotNull BufferedImage source, @NotNull BufferedImage dest, int xpos, int ypos) {
        checkArgument(source.getWidth() <= dest.getWidth() + xpos);
        checkArgument(source.getHeight() <= dest.getHeight() + ypos);
        for (int y = 0; y < source.getHeight(); y++) {
            for (int x = 0; x < source.getWidth(); x++) {
                dest.setRGB(x + xpos, y + ypos, source.getRGB(x, y));
            }
        }
    }

    /**
     * Returns average color of 3 pixels without alfa
     * @param color1
     * @param color2
     * @return
     */
    public static int avgPixel(int color1, int color2, int color3) {
        return getPixel((getRPixel(color1) + getRPixel(color2) + getRPixel(color3)) / 3,
                        (getGPixel(color1) + getGPixel(color2) + getGPixel(color3)) / 3,
                        (getBPixel(color1) + getBPixel(color2) + getBPixel(color3)) / 3);
    }