Run the OpenGL shader to modify an existing texture / frame buffer

Question

How to use an OpenGL shader to modify an existing texture / frame buffer without using a second texture or frame buffer? Is it possible?

Answer 1

First: It is technically possible and safe to read and write in the same passage using this extension - however, I would not recommend it, especially for students, since the extension is very limited and may not be supported on each equipment.

Said:

So it is not possible to use the same texture as the sampler and frame buffer?

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