Convert RGB JPEG to CMYK JPEG using ColorConverterOp Java

Question

I am attempting to convert a jpeg image in rgb to CMYK colorspace. The only problem is my final output is always a black image. But interesting enough the preview application in MAC shows the image correctly. There does not seem to be an example of a successful rgb to cmyk conversion anywhere I've looked so far. Below is the code i'm using to attempt the conversion. This code works fine If i'm performing the conversion to rgb using RGB ICC Profile. Any guidance is greatly appreciated.

import javax.imageio.ImageIO;

public class TestClass {

  public static void main(String[] args) throws Exception {
    BufferedImage cmykImage = ImageIO.read(new File(
            "CMYK_Sample.jpg"));     
    BufferedImage rgbImage = null;

    ColorSpace cpace = new ICC_ColorSpace(ICC_Profile.getInstance(TestClass.class.getClassLoader().getResourceAsStream("icc/USWebCoatedSWOP.icc")));

    ColorConvertOp op = new ColorConvertOp(cpace, null);       
    rgbImage = op.filter(cmykImage, null);

    ImageIO.write(rgbImage, "JPEG", new File("CMYK_Sample_RGB_OUTPUT2.jpg"));

  }
}

How do you know the image is always black? What software are you using to determine that, and why is that software supposed to be more reliable than the preview app on Mac? — Codo
OK maybe the right term would be "it appears to be black", and this is true in Gimp and Photoshop and Ubuntu preview app & Image Viewer. As far as reliability I don't think I implied that I think either is more reliable that the other. I just pointed out that mac preview seems to show me what I expect, and its not the same for the other applications. — mtanzania

Gangnus Gangnus · Accepted Answer · 2011-11-18T22:39:39

CMYK is for printing. So, there are few possibilities to show it, except of pdf and postscript files. JPEG can show almost only RGB. So, in your last line ImageIO.write you are trying to read cmyk as RGB. Here is the problem.

CMYK in JPEG:"Adobe Photoshop and some other prepress-oriented applications will produce four-channel CMYK JPEG files when asked to save a JPEG from CMYK image mode. Hardly anything that's not prepress-savvy will cope with CMYK JPEGs (or any other CMYK format for that matter). When making JPEGs for Web use, be sure to save from RGB or grayscale mode." (http://www.faqs.org/faqs/jpeg-faq/part1/)

As for showing CMYK files in java, use java-2d (http://download.oracle.com/javase/1.3/docs/guide/2d/spec/j2d-color.fm2.html)

Convert RGB JPEG to CMYK JPEG using ColorConverterOp Java

1 Answers