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Blender compositor seperate and combine rgba yields different image.
Open, Needs TriagePublic

Description

System Information
Operating system: Windows 10 Pro
Graphics card: GTX 1080ti

Blender Version
Broken: 2,80, 91a155833e59
Also happens in most recent 2.7

Short description of error
When inputting and image, splitting the color channels and recombining them. The output is different than the original even though it shouldn't be


(The image above shows the Alpha channel from the image input node not being used. However, using that yields the same results.
Here's a better view of how blender changes the image. It doesn't just change the colors, but the smooth gradients from the original image are "corrupted" in a way.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

  1. create an image input node and load the image from this file{F6266631}
  2. attach the Image output to the input of a "Seperate RGBA" node
  3. attach the outputs of "Seperate RGBA" node to the corrosponding inputs on a "Combine RGBA" node
  4. attach the output of the "Combine RGBA" node to a file output node with TGA RGBA format
  5. render and compare input and output

Details

Type
Bug