from ij import *
from ij.process import *
from ij.measure import *
from ij.gui import *
from java.lang import Math

imp = IJ.openImage("https://datamelt.org/logo.png")
# imp.show()

# get pixel array
pix = imp.getProcessor().convertToFloat().getPixels()
print pix
# find out the minimal pixel value
min = reduce(Math.min, pix)
 
# create a new pixel array with the minimal value subtracted
pix2 = map(lambda x: x - min, pix)
 
img1=ImagePlus("min subtracted", FloatProcessor(imp.width, imp.height, pix2, None))
img1.show()