import java.awt.Image; import java.awt.color.ColorSpace; import java.awt.image.BufferedImage; import java.awt.image.ColorConvertOp; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import javax.imageio.ImageIO; import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGImageEncoder; public class ImageUtil {
      public static void main(String[] args) throws Exception {
          File file=new File("C:\\Users\\pc\\Desktop\\cd.jpg");         changeImge(file);     }     /**      * * 转换图片 * *      */     public static void changeImge(File img) {
          try {
              Image image = ImageIO.read(img);             int srcH = image.getHeight(null);             int srcW = image.getWidth(null);             BufferedImage bufferedImage = new BufferedImage(srcW, srcH,BufferedImage.TYPE_3BYTE_BGR);             bufferedImage.getGraphics().drawImage(image, 0,0, srcW, srcH, null);             bufferedImage=new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY),null).filter (bufferedImage,null);             FileOutputStream fos = new FileOutputStream(img);             JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(fos);             encoder.encode(bufferedImage);             fos.close();         } catch (IOException e) {
              e.printStackTrace();             throw new IllegalStateException("图片转换出错！", e);         }     } }