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Render Result exists in bpy.data.images["Render Result"] but it contains no data.

Also bpy.data.images["Render Result"].size[0] is 0, even if the render shows as an image in the UV/Image Editor with a width of 1366.

Maybe the render result cannot be accessed as an image or I missing some update or refresh call somewhere but I can't find such a thing in the 2.68 API documentation.

Any tip in the correct direction appreciated.

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2 Answers

up vote 1 down vote

Last time I experimented with this, it was necessary to save the content of Render Result as an image to disk and then load it as a new image. Then the pixel array is accessible. Maybe this API feature can be improved, or i'm doing it wrong :)

import bpy

bpy.data.images['Render Result'].save_render("somefile.tga")
r2 = bpy.data.images.load("somefile.tga")
r2.pixels[0] = 0.2345
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Thank you. Indeed, pixel data is accessible if the image has a file path and is saved first. But the render I want to read from is generated by the script (by calling bpy.ops.render()). If I render with F12, assign a file path to the render result and save, the next time I call bpy.ops.render() Blender generated a new image called "Render Result.001", It does not use the "Render Result" image any more. – Hatoru Hansou Aug 6 at 21:09
yeah, i'm going to avoid suggesting that you keep track of All images with string "Render Result" and sort them and access the last index -1, perhaps someone else can offer enlightenment. – zeffii Aug 6 at 21:14
up vote 0 down vote accepted

Answering myself, if somebody find a better solution please answer and I will change my accepted answer.

The only reliable way to access the render result pixels is this:

1- Save the actual value of bpy.data.scenes["Scene"].render.filepath to a local variable

2- Set bpy.data.scenes["Scene"].render.filepath to something to avoid overwriting any previous render, for example "//temp." + str(time.time()) + ".png". 1 and 2 can be ignored if you don't care of any previous render.

3- Call bpy.ops.render.render(write_still=True). write_still set to true will cause the file to be immediately written to disk.

4- Create a new image and load that file from disk, or use an existing image reserved for this purpose in your blend file and set its filepath and then reload.

5- Do what you need to do with the loaded image pixels.

6- Remove the loaded image, except you have a good reason to keep it in the blend file.

7- Restore the original value of bpy.data.scenes["Scene"].render.filepath

In resume: the only reliable way to access pixel data of a render is to render it, save to disk immediately, recover from disk, read pixel data.

At the time of writing this, Blender version is 2.68.

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