Split 4-channel .tif UAV image to separate files according to the channel

Python
1

Hello, I’ m trying to separate a UAV .tif (containing four channels: green, red, red-edge, NIR) to four different images, one for each channel. The code that I used for normal RGB (3 channel .tif) worked perfectly but I when I try to implement it to the 4-channel UAV .tif image with the related modifications in the code, I get this message…

  File "code.py", line 4, in <module>
    g,r,re,nir = cv2.split(img)
ValueError: not enough values to unpack (expected 4, got 0)

Any idea how to fix this?

2

  1. check img.shape
    you probably loaded the image without IMREAD_UNCHANGED, which means OpenCV automatically converts it to (some type of) BGR, losing the extra channel
    it may still reorder the channels. I don’t know exactly how it’ll behave. check the docs and/or run the function and check the results to be sure.

  2. you’re using python. you can also use numpy means:
    (ch1, ch2, ch3, ch4) = np.transpose(img, axes=(2,0,1))

1 Like
3

Thanks, solution 1 works! But how can be sure which channel is which? With gdalinfo I get only the Green correctly and other 3 as undefined…

4

don’t expect OpenCV to give you the original tiff data.

you may have to use the tifffile package

1 Like
5

I tried both openCV and tifffile but I lose the real coordinates in the end result… How can I avoid this?

6

this is the first time you mentioned coordinates.

1 Like
7

Yes, this is true! I did not know that the coordinates are affected though!

8

do you think you should explain what you mean?

9

Ok, the idea is to have unaffected the coordinates after the calculations with the images… How do I achieve this?

10

maybe you never meant “coordinates”,
but that the “order/meaning of the channels” has changed ?

11

Ok! How do I maintain the coordinates?