I use the Java ImageIO libraries (https://jai-imageio.dev.java.net). They aren't perfect, but can be simple and get the job done. As far as converting from CMYK to RGB, here is the best I have been able to come up with.
Download and install the ImageIO JARs and native libraries for your platform. The native libraries are essential. Without them the ImageIO JAR files will not be able to detect the CMYK images. Originally, I was under the impression that the native libraries would improve performance but was not required for any functionality. I was wrong.
The only other thing that I noticed is that the converted RGB images are sometimes much lighter than the CMYK images. If anyone knows how to solve that problem, I would be appreciative.
Below is some code to convert a CMYK image into an RGB image of any supported format.
Thank you,
Randy Stegbauer
package cmyk;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import org.apache.commons.lang.StringUtils;
public class Main
{
/**
* Creates new RGB images from all the CMYK images passed
* in on the command line.
* The new filename generated is, for example "GIF_original_filename.gif".
*
*/
public static void main(String[] args)
{
for (int ii = 0; ii < args.length; ii++)
{
String filename = args[ii];
boolean cmyk = isCMYK(filename);
System.out.println(cmyk + ": " + filename);
if (cmyk)
{
try
{
String rgbFile = cmyk2rgb(filename);
System.out.println(isCMYK(rgbFile) + ": " + rgbFile);
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
}
}
}
/**
* If 'filename' is a CMYK file, then convert the image into RGB,
* store it into a JPEG file, and return the new filename.
*
* @param filename
*/
private static String cmyk2rgb(String filename) throws IOException
{
// Change this format into any ImageIO supported format.
String format = "gif";
File imageFile = new File(filename);
String rgbFilename = filename;
BufferedImage image = ImageIO.read(imageFile);
if (image != null)
{
int colorSpaceType = image.getColorModel().getColorSpace().getType();
if (colorSpaceType == ColorSpace.TYPE_CMYK)
{
BufferedImage rgbImage =
new BufferedImage(
image.getWidth(), image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
ColorConvertOp op = new ColorConvertOp(null);
op.filter(image, rgbImage);
rgbFilename = changeExtension(imageFile.getName(), format);
rgbFilename = new File(imageFile.getParent(), format + "_" + rgbFilename).getPath();
ImageIO.write(rgbImage, format, new File(rgbFilename));
}
}
return rgbFilename;
}
/**
* Change the extension of 'filename' to 'newExtension'.
*
* @param filename
* @param newExtension
* @return filename with new extension
*/
private static String changeExtension(String filename, String newExtension)
{
String result = filename;
if (filename != null && newExtension != null && newExtension.length() != 0);
{
int dot = filename.lastIndexOf('.');
if (dot != -1)
{
result = filename.substring(0, dot) + '.' + newExtension;
}
}
return result;
}
private static boolean isCMYK(String filename)
{
boolean result = false;
BufferedImage img = null;
try
{
img = ImageIO.read(new File(filename));
}
catch (IOException e)
{
System.out.println(e.getMessage() + ": " + filename);
}
if (img != null)
{
int colorSpaceType = img.getColorModel().getColorSpace().getType();
result = colorSpaceType == ColorSpace.TYPE_CMYK;
}
return result;
}
}