Viewing Images

Viewing Image Data within ImageJ2 Java Code Brian Northan, True North Intelligent Algorithms LLC

Viewing Images

  • https://bnorthan.github.io/viewing-images-tutorial/slides/
  • Code
  • Images
  • Put images beside (not in) 'learnathon-2019'


  1. Learn to show images within Java programs using both ImageJ1 and ImageJ2
  2. Learn to access ImageJ1 Visualization routines from your java program
  3. Learn how to use ImageJ2 API (ops, imglib2, Views, etc.) for basic visualization
    • Ops and Imglib2 will be explained in detail in later sessions
  4. Learn to display multidimensional and complex data
  5. Basic use of imglib2 to render data

Example 1 Open and Display Images

  • Open Image using IJ1 and IJ2 API
  • Open up an Image Display inside programs
  • Display result of command using annotation

Start ImageJ

// create an instance of imagej
final ImageJ ij = new ImageJ();

// launch it


Open Some Image Data

  • ImageJ1 ImagePlus
  • ImageJ2 Dataset

// get bridge as IJ1 ImagePlus (imp)
ImagePlus impBridge = IJ.openImage("../images/bridge.tif");

// get bridge as IJ2 Dataset
// Dataset
Dataset datasetBridge = (Dataset) ij.io().open("../images/bridge.tif");


Display Image using IJ1

// show the IJ1 ImagePlus
impBridge.setTitle("ImageJ1 ImagePlus");

Display Image using IJ2 UIService

// show the IJ2 Dataset
ij.ui().show("Bridge IJ2 ij.ui().show", datasetBridge);

Display Image using IJ2 ImageJFunctions

// show using imagej functions
ImageJFunctions.show((RandomAccessibleInterval) datasetBridge
	.getImgPlus()).setTitle("Bridge IJ2 ImageJFunctions.show");

Display output of Command

  • Framework does it automatically

@Parameter(type = ItemIO.OUTPUT)
Img out;

public void run() {
	out = ops.create().img(in);
	ops.filter().addPoissonNoise(out, in);

Example 2 Mixed World

  • Open Image and process using IJ2
  • Display using IJ1 API
  • Re-use legacy code to show a colormap
  • Use IJ1 API for line profiles

Start IJ, load image and blur it

// create an instance of imagej
final ImageJ ij = new ImageJ();

// launch it

// get bridge as IJ2 Dataset
Dataset dataBridge = (Dataset) ij.io().open("../images/bridge.tif");

// blur the bridge
RandomAccessibleInterval blurred = ij.op().filter().gauss(
	(RandomAccessibleInterval) dataBridge, 3.0);

Convert to IJ1 and show...

// convert bridge to IJ1
ImagePlus impBridge = ImageJFunctions.wrap(
(RandomAccessibleInterval) dataBridge, "bridge");
// convert blurred to IJ1
ImagePlus impBlurred = ImageJFunctions.wrap(blurred, "blurred");

// show IJ1

Scavenge 'fire' LUT from IJ1 LutLoader

  • [Ctrl] [Shift] [T] then search for LutLoader
  • Look for fire method (not public??)
  • Scavenge fire and interpolate functions

// get the fire color map using the Utility
// (note the code in the Utility was cut and pasted from LutLoader
// I couldn't figure out how to cleanly grab the fire LUT from it....
LUT lut = IJ2CourseImageUtility.fire();

// set the LUT on the bridge and blurred



Use IJ1 API to draw line profiles

  • Line profiles are useful for before and after comparisons

// now draw an ROI (using the IJ1 interface) on each image and plot it
impBridge.setRoi(new Line(100, 100, 200, 200));
impBlurred.setRoi(new Line(100, 100, 200, 200));
ProfilePlot plotter1 = new ProfilePlot(impBridge);
ProfilePlot plotter2 = new ProfilePlot(impBlurred);

  • Run your favourite IJ1 routine
  • Use Plugins->Macros->Record...(java)

Example 3a Viewing cropped intervals

  • Use ops to crop
  • Alternatively use Views
  • More on ops and Views in a later session
  • Draw a sphere on the data
    • What happens on the RAI?

Interval interval = Intervals.createMinMax(100, 100, 20, 400, 400, 40);

// crop interval
RandomAccessibleInterval raiVolume = (RandomAccessibleInterval) ij
	.op().transform().crop(image, interval);

// alternatively you can use Views directly
RandomAccessibleInterval rai2 = (RandomAccessibleInterval) Views
	.interval(image, interval);

// display the image
ij.ui().show("RAI volume", raiVolume);
  • Note "ops time" and "views time"
  • Why are they different?"

Draw Sphere Command

@Plugin(type = Command.class,
	menuPath = "Plugins>Learnathon>Draw A Sphere (IJ2)")
public class DrawSphereInCenter & NativeType>
	implements Command

	OpService ops;

	Img img;

	public void run() {
		final Point center = new Point(img.numDimensions());

		for (int d = 0; d < img.numDimensions(); d++)
			center.setPosition(img.dimension(d) / 2, d);

		long radius = Math.min(img.dimension(0), Math.min(img.dimension(1), img

		T intensity = ops.stats().max(Views.iterable(img));

		HyperSphere hyperSphere = new HyperSphere<>(img, center, radius);

		for (final T value : hyperSphere) {

Example 3b Out of bounds?

What if the Interval is out of bounds

Interval interval = Intervals.createMinMax(-100, 100, 200, 700);
// Try cropping with an interval that goes out of bounds... 
RandomAccessibleInterval rai = (RandomAccessibleInterval) Views
	.interval(image, interval);

// try again but extend image... (comment out above code, comment in this code)
//RandomAccessibleInterval rai = (RandomAccessibleInterval) Views
	//	.interval(Views.extendZero(image), interval);

// display the image
ij.ui().show("RAI", rai);

Try again...

Interval interval = Intervals.createMinMax(-100, 100, 200, 700);
// Try cropping with an interval that goes out of bounds... 
//RandomAccessibleInterval rai = (RandomAccessibleInterval) Views
//	.interval(image, interval);

// try again but extend image... (comment out above code, comment in this code)
RandomAccessibleInterval rai = (RandomAccessibleInterval) Views
		.interval(Views.extendZero(image), interval);

// display the image
ij.ui().show("RAI", rai);

Example 3c crop hyperslice

Show axis info using dimension index

for (int d = 0; d < image.numDimensions(); d++) {

Show axis size using axis enumeration

int xIndex = image.dimensionIndex(Axes.X);
int yIndex = image.dimensionIndex(Axes.Y);
int zIndex = image.dimensionIndex(Axes.Z);
int cIndex = image.dimensionIndex(Axes.CHANNEL);
int tIndex = image.dimensionIndex(Axes.TIME);

long xLen = image.dimension(image.dimensionIndex(Axes.X));
long yLen = image.dimension(image.dimensionIndex(Axes.Y));
long zLen = image.dimension(image.dimensionIndex(Axes.Z));
long cLen = image.dimension(image.dimensionIndex(Axes.CHANNEL));
long tLen = image.dimension(image.dimensionIndex(Axes.TIME));

Crop Hyperslice using axis index and position

// we can use Views to get a hyperslice using a dimensions index and position
RandomAccessibleInterval raiViews = (RandomAccessibleInterval) Views
	.hyperSlice(image, cIndex, 0);

Convert to ImgPlus and set axis

// display the image... note that something isn't quite right
ij.ui().show("RAI volume", raiViews);

// the cropped section is an RAI. To get it to display correctly we need to
// use the dtaasetservice to convert it to an ImgPlus with ocrrect axis
DatasetService datasetService = ij.dataset();
AxisType[] axisTypes = new AxisType[] { Axes.X, Axes.Y, Axes.Z,
	Axes.TIME };
ImgPlus imgPlusVolume = new ImgPlus(datasetService.create(raiViews), "image",

// now the viewer should display the image with correct axis
ij.ui().show("ImgPlus volume", imgPlusVolume);

Example 4a Permutions

Permute (Reslice) using Views to see xz slices

  • last 2 parameters are 'from' and 'to'
  • Switch 1 (y) and 2 (z)

IntervalView dataXZY = Views.permute((RandomAccessibleInterval) data,
	1, 3);

ij.ui().show("Data XZY", dataXZY);

Example 4b Projections

Projections using ops

long[] projectedDimensions = new long[imgPlus.numDimensions() - 1];

int projectedDimensionIndex = imgPlus.dimensionIndex(ax);

int i = 0;

for (int d = 0; d < imgPlus.numDimensions(); d++) {
	if (d != projectedDimensionIndex) {
		projectedDimensions[i] = imgPlus.dimension(d);

Img projection = ops.create().img(new FinalDimensions(
	projectedDimensions), imgPlus.firstElement());

UnaryComputerOp, T> projector = Computers.unary(ops, projectType,
	projection.firstElement(), imgPlus);

return ops.transform().project(projection, imgPlus,
	(UnaryComputerOp) projector, projectedDimensionIndex);


Example 5 - Rendering points

  • By the end of the week you should be able to...
    • Use imglib2 to render points as Gaussian
    • Use Cursors to loop through data (pixels and more...)
    • Understand how to get and set 'Types'
    • Understand how to perform operations on 'Types'
  • This code adds a Gaussian to an image
  • May not make sense yet...
  • It should by the end of the week
    // get the RAI to draw the Gaussian in
    RandomAccessibleInterval rai = Views.interval(img,
    	new FinalInterval(start, end));
    Cursor c1 = Views.iterable(Views.zeroMin(rai)).cursor();
    Cursor c2 = Views.iterable(guassian).cursor();
    while (c1.hasNext()) {
  • Synaptic Clefts (from Jon Bogovic)
  • More to come with this data next session...

Example 6 - Complex Numbers

Perform FFT using ops, Display real and complex parts

RandomAccessibleInterval fft=ij.op().filter().fft(impBridge);

// default is power spectrum
ImageJFunctions.show(fft).setTitle("fft power spectrum");
// real values
ImageJFunctions.show(fft, new ComplexRealFloatConverter()).setTitle("fft real values");
// imaginary values
ImageJFunctions.show(fft, new ComplexImaginaryFloatConverter()).setTitle("fft imaginary values");
  • Perform an FFT and show complex and real parts