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ImageJ1-ImageJ2 cheat sheet

This page summarizes translation of basic operations of ImageJ1 and ImageJ2 API. Based on the work of Robert Haase , Scientific Computing Facility, MPI-CBG Dresden.




Starting ImageJ

new ij.ImageJ();
ImageJ ij = new net.imagej.ImageJ();

Show images

imp is an ImagePlus object

Retrieve an active image object

ImagePlus imp = IJ.getImage();

Script parameter (the same for Dataset, ImagePlus, etc.):

#@ Img image

In Java code:

private Img image;

Using ImageDisplayService:

Dataset image = ij.imageDisplay().getActiveDataset();

Open an image file

IJ.openImage() returns an ImagePlus object without showing.

ImagePlus imp = IJ.openImage(urlOrFilePath);; automatically shows the image without returning ImagePlus.;
ImagePlus imp = IJ.getImage();

Using IOService:

Object image =;

Using DatasetIOService (for type safety):

Dataset image = ij.scifio().datasetIO().open(urlOrFilePath);

Save an image file

IJ.saveasTiff(imp, "/path/to/image.tif")

Using IOService:, "/path/to/image.tif");

Using DatasetIOService:

ij.scifio().datasetIO().save(dataset, "/path/to/image.tif");

Convert image types

Convert from ImageJ2 Img object to ImageJ1 ImagePlus object:

ImagePlus imp = ImageJFunctions.wrap(img,"Title");

Convert from ImageJ1 ImagePlus object to ImgLib2 Img object:

Img<T> realImg = ImageJFunctions.wrapReal(imp);
Img<FloatType> floatImg = ImageJFunctions.convertFloat(imp);
Img<FloatType> realImg2 = ImageJFunctions.wrap(imp);

Show regions

Img<BitType> mask; // = ...
ImagePlus maskImp =ImageJFunctions.wrap(mask, "mask");
// threshold the mask to get an ROI
ImageProcessor imageProcessor = maskImp.getProcessor();
imageProcessor.setThreshold(128,128,ImageProcessor NO_LUT_UPDATE);
Roi roi = new ThresholdToSelection().convert(imageProcessor);

Run plugins,"Normalisation","");
ij.command().run(ImageNormalizerIJ2Plugin.class, true, "input", img, "ij", ij);

Define plugins

public class ImageNormalizerPlugin implements PluginFilter {

In resources/plugins.config:

Plugins>Filtering, "Normalisation", NormalizerPlugin
@Plugin(type = Command.class, menuPath = "Plugins>Normalization")
public class ImageNormalizerIJ2Plugin implements Command {

See also