Re: problem with imageconversion in ImageJ api

Knute Johnson <>
Fri, 09 Oct 2009 09:57:29 -0700
harryos wrote:

I tried to convert an image to 8bit grayscale using imageJ api.
The code snippet is as follows

import ij.IJ;
import ij.ImagePlus;
import ij.process.ImageConverter;
import java.awt.image.BufferedImage;

public static void toGrayscale(){
    ImagePlus imp=new ImagePlus("F:\\myimgs\\Picture 001.jpg");
    if (imp.getType() == ImagePlus.GRAY8){
    System.out.println("orig image color mode="+imp.getType());
    ImageConverter ic = new ImageConverter(imp);
    IJ.saveAs(imp, "png", "F:\\myimgs\\newimage.png");
    BufferedImage bufferedImage=imp.getBufferedImage();
    if (imp.getType() == ImagePlus.GRAY8){
        System.out.println("after conversion, type is gray8");
            System.out.println("bufferedImage type is="+
        System.out.println("still imp is="+imp.getType());
                System.out.println("bufferedimg type



however ,when I run this using a truecolor image,I get the following

orig image color mode=4 // TYPE_INT_BGR
after conversion, type is gray8
bufferedimg type is=13 // TYPE_BYTE_INDEXED

I am confused by the value 13.Shouldn't it be 10 viz TYPE_BYTE_GRAY ?
can someone tell me why this is happening?
thanks a lot

I don't know ImageJ but it is easy to do with plain old Java.

     public static BufferedImage convertToGray(BufferedImage image) {
         BufferedImage gray = new BufferedImage(image.getWidth(),
         ColorConvertOp op = new ColorConvertOp(
         return gray;


Knute Johnson
email s/nospam/knute2009/

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