这个代码是我在网上找的，可以运行。

package com.pb.util;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

import java.awt.Transparency;

import java.awt.color.ColorSpace;

import java.awt.image.BufferedImage;

import java.awt.image.ColorModel;

import java.awt.image.ComponentColorModel;

import java.awt.image.DataBuffer;

import java.awt.image.DataBufferByte;

import java.awt.image.Raster;

import java.awt.image.WritableRaster;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.util.Iterator;

import javax.imageio.IIOException;

import javax.imageio.ImageIO;

import javax.imageio.ImageReader;

import javax.imageio.stream.ImageInputStream;

/**

* 把cmyk格式图片转换为RGB格式

* @author Administrator

*

*/

public class CMYK {

public void readImage(String filename) throws IOException {

File file = new File(filename);

ImageInputStream input = ImageIO.createImageInputStream(file);

Iterator readers = ImageIO.getImageReaders(input);

if(readers == null || !readers.hasNext()) {

throw new RuntimeException("1 No ImageReaders found");

}

ImageReader reader = (ImageReader) readers.next();

reader.setInput(input);

String format = reader.getFormatName() ;

BufferedImage image;

if ( "JPEG".equalsIgnoreCase(format) ||"JPG".equalsIgnoreCase(format) )   {

try {

// 尝试读取图片 (包括颜色的转换).

image = reader.read(0); //RGB

} catch (IIOException e) {

// 读取Raster (没有颜色的转换).

Raster raster = reader.readRaster(0, null);//CMYK

image = createJPEG4(raster);

}

image.getGraphics().drawImage(image, 0, 0, null);

//String newfilename = filename.substring(0,filename.lastIndexOf("."))+"_rgb"+filename.substring(filename.lastIndexOf("."));

String newfilename = filename;

File newFile = new File(newfilename);

FileOutputStream out = new FileOutputStream(newFile);

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

encoder.encode(image);

out.flush();

out.close();

}

}

private static BufferedImage createJPEG4(Raster raster) {

int w = raster.getWidth();

int h = raster.getHeight();

byte[] rgb = new byte[w * h * 3];

//彩色空间转换

float[] Y = raster.getSamples(0, 0, w, h, 0, (float[]) null);

float[] Cb = raster.getSamples(0, 0, w, h, 1, (float[]) null);

float[] Cr = raster.getSamples(0, 0, w, h, 2, (float[]) null);

float[] K = raster.getSamples(0, 0, w, h, 3, (float[]) null);

for (int i = 0, imax = Y.length, base = 0; i < imax; i++, base += 3) {

float k = 220 - K[i], y = 255 - Y[i], cb = 255 - Cb[i],

cr = 255 - Cr[i];

double val = y + 1.402 * (cr - 128) - k;

val = (val - 128) * .65f + 128;

rgb[base] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff

: (byte) (val + 0.5);

val = y - 0.34414 * (cb - 128) - 0.71414 * (cr - 128) - k;

val = (val - 128) * .65f + 128;

rgb[base + 1] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff

: (byte) (val + 0.5);

val = y + 1.772 * (cb - 128) - k;

val = (val - 128) * .65f + 128;

rgb[base + 2] = val < 0.0 ? (byte) 0 : val > 255.0 ? (byte) 0xff

: (byte) (val + 0.5);

}

raster = Raster.createInterleavedRaster(new DataBufferByte(rgb, rgb.length), w, h, w * 3, 3, new int[]{0, 1, 2}, null);

ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_sRGB);

ColorModel cm = new ComponentColorModel(cs, false, true, Transparency.OPAQUE, DataBuffer.TYPE_BYTE);

return new BufferedImage(cm, (WritableRaster) raster, true, null);

}

//测试

public static void main(String[] args) throws IOException {

String filename = "d:/2015.jpg";

CMYK cm = new CMYK();

cm.readImage(filename);

}

}