Texture taken from Item: can I make its filtering be gamma-correct?

Question

If this was a texture that I created, I'd simply make its internalFormat be GL_SRGB. But I'm passing a Qt Quick Item foo into my custom QQuickFramebufferObject GL code, where I take foo->textureProvider()->texture() and use that texture to render.

So can I make the filtering of the texture (when bilinearly sampling it) be gamma-correct?

Note: I'm aware I could implement manual bilinear filtering with 4 texture taps and lerping, but that would hurt performance somewhat, so I'm looking for a better way.

Or I could blit from the Qt Quick texture into a GL_SRGB texture of my own, then use that texture, but that's more complex and would need to happen every time the source texture is updated, hurting performance (and RAM usage).

I've searched google for hooks Qt may provide to configure this, but found nothing except QQuickTextureFactory which, however, does not solve my problem, at least AFAICS.

I need to support OpenGL ES 2.0.

Answer 1

Note: I'm aware I could implement manual bilinear filtering with 4 texture taps and lerping, but that would hurt performance somewhat, so I'm looking for a better way.

Well, from the filtered result color, there is simply no way to get back the original colors used as input, even if you know the interpolation factors.

Or I could blit from the Qt Quick texture into a GL_SRGB texture of my own, then use that texture, but that's more complex and would need to happen every time the source texture is updated, hurting performance (and RAM usage).

A more efficient variation of this strategy would be creating a second view onto the texture data, with an SRGB format (see GL_ARB_texture_view extension, core since GL 4.3), which completely avoids the copy and additional RAM usage.