ConvertRGBstackTo32bitHyperstack.py

from ij import IJ, ImagePlus, ImageStack, CompositeImage  
  
# Load a stack of images: a fly brain, in RGB  
imp = IJ.openImage("https://imagej.nih.gov/ij/images/flybrain.zip")  
stack = imp.getImageStack()  
  
# A new stack to hold the data of the hyperstack  
stack2 = ImageStack(imp.width, imp.height)  
  
# Convert each color slice in the stack  
# to two 32-bit FloatProcessor slices  
for i in xrange(1, imp.getNSlices()+1):  
  # Get the ColorProcessor slice at index i  
  cp = stack.getProcessor(i)  
  # Extract the red and green channels as FloatProcessor  
  red = cp.toFloat(0, None)  
  green = cp.toFloat(1, None)  
  # Add both to the new stack  
  stack2.addSlice(None, red)  
  stack2.addSlice(None, green)  
  
# Create a new ImagePlus with the new stack  
imp2 = ImagePlus("32-bit 2-channel composite", stack2)  
imp2.setCalibration(imp.getCalibration().copy())  
  
# Tell the ImagePlus to represent the slices in its stack  
# in hyperstack form, and open it as a CompositeImage:  
nChannels = 2             # two color channels  
nSlices = stack.getSize() # the number of slices of the original stack  
nFrames = 1               # only one time point   
imp2.setDimensions(nChannels, nSlices, nFrames)  
comp = CompositeImage(imp2, CompositeImage.COLOR)  
comp.show()