Transparent output

[Juan Nunez-Iglesias]

Steve, that is a *great* catch!!! =D

On Fri, Feb 6, 2015 at 1:19 PM, Steven Silvester
<steven.silvester at gmail.com> wrote:

> Marcel,
> When you say the output image was transparent, you mean it was all white?  
> I believe what happened is your call to `np.empty` creates a floating point 
> array, which skimage expects to be in the range [0, 1], but your data is in 
> the range [0, 255].  If you used `dtype=np.uint8` in your `np.empty` call, 
> I suspect it would work.
> Regards,
> Steve
> On Wednesday, February 4, 2015 at 9:22:44 AM UTC-6, Marcel Gutsche wrote:
>>
>> 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
>>
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