Render an image into the window

[shoham-z]

Hey,
Is there any way i can render an image and display it directly to the app window?
After I render the image I have it stored as an array of RGB values (0-255).

[JamesBoer]

There is, although it's not supported by ImFrame explicitly. Rather, the glfw main window is an OpenGL context. ImFrame does offer a convenience function LoadTextureFromFile() which loads an OpenGL texture from an image on disk, which can then either be used by ImGui or OpenGL for whatever you want.

In this case, since the background is an OpenGL context, so you'll need to use OpenGL to render a textured quad. You can see in the Features example GLDemo.cpp demonstrates how to render a rotating colored triangle using vertex and fragment shaders. You can use this as a starting point for creating a fragment shader that supports textures as well. You should be able to find tutorials available on the web for using OpenGL to do things like this.

[shoham-z]

I built my own ray tracer, and have the image stored as rgb values in an array before i save it to the disk as ppm file.
Is there a way to use that array to color pixels individually?

[JamesBoer]

Sure, but you'll have to write the OpenGL code to create a texture from that rgb array, plus width and height, of course. If you look at ImFrame's LoadTextureFromFile() function, you can see how this is done. After the code to load the image into an array, most of the rest of the code is the same.

I think the only difference is that you'd pass GL_RGB to glTexImage2D() instead of GL_RGBA, since you aren't using an alpha channel.

Once you have that GLTexture (just an index handle), you can then use it to display a textured quad on the screen.

[shoham-z]

you can then use it to display a textured quad on the screen.
How exactly do I do that? Is there an example?

[shoham-z]

Thank you.

And how can I load the changes the window?

[JamesBoer]

Do you mean how you display the image in the window?

As I mentioned, there's an example of drawing a colored triangle in one of the Features in GLDemo.cpp. Drawing a textured quad is not all that much different, but probably a bit too involved for me to easily describe. OpenGL is pretty low level, so there's a lot of boilderplate to write even to do something fairly simple like this.

I searched "opengl draw textured quad", and this was the first result. You could also use a shader-based approach, like in my example code, but this is probably simpler for your case. Note that the framework handles what's in main() and render(), so no need to do that.

[shoham-z]

You are talking about main() and render(), but I started working with the Minimal example, but the line that seems to be starting the code is IMFRAME_MAIN("ImFrame", "Game Demo", MainApp)

[JamesBoer]

What I meant was, in the link I shared with you (on StackOverflow), there are OpenGL or glut functions in the main() and render() functions. My point was that you don't need to worry about those, since ImFrame already takes care of basic OpenGL updates and rendering. Does that make more sense?

[shoham-z]

Yup, it does. I added the call for LoadTexture() inside OnUpdate(), like this: this->LoadTexture();, but the image doesn't load. Feels like I need to do something with the value coming from LoadTexture(), but I don't know what it is.
I tried doing it like this but still no luck: auto ret = this->LoadTexture(); if (ret) { if (this->m_texture.textureID) glDeleteTextures(1, &this->m_texture.textureID); this->m_texture = ret.value(); m_showTexture = true; }
BTW I'm new to opengl and GUI programming, so I'm even more lost.

[JamesBoer]

So, what are you doing in LoadTexture()? It should look pretty close to ImFrame's LoadTextureFromFile(), except for the first part of the code that loads from disk, since you already have the raw image bits in memory.

[shoham-z]

Do I just call LoadTexture() and do not worry about the return value?

[JamesBoer]

Sorry to take so long to get back to you. I've been switching over to a new computer since my old one was having issues. Hopefully will have things set up in the next day or so.