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I'm trying to get a black and white image from an image with an alpha-channel in the Eeevee renderer.

  • alpha -> black
  • rest -> white

I used the alpha-channel from the picture with a GreaterThan-node to get only 1 and 0. To get an image again I used the ColorRamp Node (set to constant - black and white)

My node-tree in the compositor

For some reason the outputimage is gray instead of white and has two different values (RGB 207:207:207 and 206:206:206). The background is black but also changes between 0:0:0 and 1:1:1. I exported in BMP and PNG (0% compression), I also double checked the colors in the ColorRamp-node.

  • Does anyone know why the ColorRamp-node behaves that way or if this could be another problem?

I'm thankful for every suggestion.

  • $\begingroup$ Your issue is probably color management, set it to Standard in the Render Settings. But why do you want a black and white image? Without anti-aliasing it's going to cause issues in most situations - I cannot think of one that it is good for. What is it for? $\endgroup$ – Martynas Žiemys Sep 30 '19 at 10:26
  • $\begingroup$ Hi Martin, thank you very mutch for your help! Setting the colormanagement to standart helped getting the cube to show white. But the background has still the type of non visible noise switching between 0:0:0 and 1:1:1. My goal is to do a mask similar to the MaskID/Object Index in Cycles. For simplicity I only want BW as the picture will be used to determine where in the image the cube/object is. (And sorry for the late reply, I had to merch accounts because I coundn't log on to this account anymore. I didn't know why) $\endgroup$ – guest_user Oct 1 '19 at 6:22
  • $\begingroup$ Using black and white(2bit) images as masks is not a good idea Blender's material and object IDs included. They will produce serious issues at the edges. Look into using Cryptomatte instead. $\endgroup$ – Martynas Žiemys Oct 1 '19 at 6:31
  • $\begingroup$ I read about Cryptomatte too, but it is unfortunately not available for eevee! But the hard edges are no problem for me, since I rather want to go for if a pixel is part of the object or not, instead of a good look. (something like the pixel is 40% the object is not so helpful for me) $\endgroup$ – guest_user Oct 1 '19 at 6:48

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