Hi all, I'm not sure if it is a bug, or whether I've just overlooked something obvious, but the internet did not offer much regarding this issue. I try to get slices from an image cube which consists of several images s = 1,...,n with the same dimensions. My new slice should have the width of the original images and the height of the number of images. Here is the code to do this: from skimage.io import ImageCollection, imsave from os.path import join import numpy as np def main(dir): ic = ImageCollection( join(dir, '*.png' ) ) row = 0 img = np.empty((len(ic), ic[0].shape[1], ic[0].shape[2] ) ) for s in range(len(ic)): img[s,...] = ic[s][row,...] # fname = 'new_{0:03d}.jpg'.format(v) # -> wrong colors fname = 'new_{0:03d}.png'.format(v) # -> output image is transparent imsave(fname, img) The problem is that the output images are all transparent. My input files are .png images with an alpha channel. I have also checked the values of the alpha channel of the output which are all set to 255, which, at least to my knowledge, should set the opacity to 100%. Regards, Marcel