quick problem description: pyrtools imshow function giving me different and negative ranges details: im following the tutorial at https://pyrtools.readthedocs.io/en/latest/tutorials/01_tools.html since i dont have .pgm image, i'm using the below .jpg image.  here is the modified python code import matplotlib.pyplot as plt import pyrtools as pt import numpy as np import cv2 # Load the JPG image oim = cv2.imread('/content/ein.jpg') print(f"input image shape: {oim.shape}") # Convert to grayscale if it's an RGB image if len(oim.shape) == 3: # Check if the image has 3 channels (RGB) oim_gray = cv2.cvtColor(oim, cv2.COLOR_BGR2GRAY) else: oim_gray = oim # Already grayscale print(f"grayscale image shape: {oim_gray.shape}") # Check the range of the oim_gray print(f"value range of oim_gray: {np.min(oim_gray), np.max(oim_gray)}") # Subsampling imSubSample = 1 im = pt.blurDn(oim_gray, n_levels=imSubSample, filt='qmf9') # Check the range of the subsampled image print(f"value range of im: {np.min(im), np.max(im)}") # Display the original and subsampled images pt.imshow([oim_gray, im], title=['original (grayscale)', 'subsampled'], vrange='auto2', col_wrap=2);  and here is the output input image shape: (256, 256, 3) grayscale image shape: (256, 256) value range of oim_gray: (4, 245) value range of im: (5.43152380173187, 251.90158197570906)  with the given image  as you can see, from the printouts, both the images oim_gray and im are in positive range. there aren't any negative values on neither im and oim_gray. but when checking the output image, i see the range -38 & 170 (please check the text over the output image). this doesn't make any sense, and don't understand. can you help on this to understand?
That is behavior of pyrtools, specifically decided by vrange='auto2'.  'auto2': all images have same vmin/vmax, which are the mean (across all images) minus/plus 2 std dev (across all images)  (documentation in source) If you don't like that library's behavior, you can file a bug at https://github.com/LabForComputationalVision/pyrtools/issues