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I am going to do millions of renderings and want to get around the IO overhead by directly storing the rendering results into Numpy arrays. To store the results into Numpy arrays, I am currently using the Viewer node to access bpy.data.images['Viewer Node'].pixels to store the pixel values. For my application, I need to make sure that each pixel value is NOT quantized to integers of range [0, 255] and then normalized to [0, 1]. Does anyone know if it is possible to access RAW values of each pixel using viewer? Or suggest an analysis method so that I asses that myself.

If people here think that it not possible to get the raw values using the Viewer node, then I need to change my rendering pipeline and store the raw data in OpenEXR files.

Also, I noticed that the image in bpy.data.images['Viewer Node'].pixels is an RGBA image although I have set bpy.context.scene.render.image_settings.color_mode to RGB. Why is that? I'm afraid the pixel values are also in 8-bit not 16-bit or 32-bit. Is there a way to make find out the number of bits used per pixel?

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  • $\begingroup$ Why not render to tiff or openexr? $\endgroup$
    – Bruno
    Mar 9 '18 at 21:40
  • $\begingroup$ @Bruno Because the IO operation quite slow in such scale. Plus, the operating system cannot handle more than a couple of million meta-data files for these many renderings and I have to write another script to deal with that. So it would be ideal if I can find out that I can get the renderings that I want via Viewer node. $\endgroup$
    – Amir
    Mar 9 '18 at 22:07
  • $\begingroup$ Got it. What about the File Output Node which would give you access to a single file rendering at a time. You would have to read and parse the file format for every frame though... $\endgroup$
    – Bruno
    Mar 9 '18 at 23:05
  • $\begingroup$ I just read the friendly manual. See my answer :) $\endgroup$
    – Bruno
    Mar 9 '18 at 23:12
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The API doc says:

pixels

Image pixels in floating point values

Type: float in [-inf, inf], default 0.0

src: https://docs.blender.org/api/blender_python_api_2_75_1/bpy.types.Image.html#bpy.types.Image

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