import java.io.File;

import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.awt.image.ColorModel;

import javax.imageio.ImageIO;

public class ColorConvertTest {

    public static void main(String[] args) throws Exception {
        BufferedImage source = ImageIO.read(
                ColorConvertTest.class.getResource("cmyk.jpg"));
        ColorModel sourceModel = source.getColorModel();
        System.out.append("< cmyk.jpg: ").println(sourceModel);

        ColorConvertOp convertOp = new ColorConvertOp(
                //sourceModel.getColorSpace(),
                ColorSpace.getInstance(ColorSpace.CS_sRGB), null);
        BufferedImage rgb = convertOp.filter(source, null);
        ImageIO.write(rgb, "png", new File("rgb.png"));
        System.out.println("> rgb.png");
    }

}