Image Drawing Module

[RobLoach]

Been wanting to use raylib's Image API outside of raylib. One use case is in a libretro core that would allow using parts of raylib on devices that Lakka supports. This would allow compiling once, and rendering in multiple different frontends that use libretro, like RetroArch.

Proof of Concept

I forked raylib's rtextures.c to its own single-header library over at rimage. Following that, I created libretro-rimage, which allows you to use the Image API in a libretro core. Using the framebuffer and raylib's Image API makes it so much easier to render things to the screen.

ImageDrawCircle(&core->backBuffer, 300, 100, 30, SKYBLUE);
ImageDrawRectangle(&core->backBuffer, 100, 100, 100, 140, GREEN);
ImageDrawLine(&core->backBuffer, 50, 50, 200, 80, ORANGE);
ImageDrawRectangle(&core->backBuffer, 20, 150, 50, 80, RED);

This fork is a big hack, and I would like a cleaner design around it so that a full fork isn't needed.

Proposed Solution

I would love to move the Image API that's done in rtextures.c into its own single-header library, similar to what was done with rl_gputex.h. This would allow using raylib's Image API outside of raylib, without requiring a complete fork.

Challenges

There are a few problems that we can run into when taking this approach....

• Duplicate function definitions
• Duplicate type names
• Having to sync things across this new single-header file and raylib.h
• Dependency issues, like having the Font stuff available to the Image API

Would love all of your thoughts. Introducing more modularity to raylib is great, but I don't want to over-complicate the code base.

[RobLoach]

Perhaps to avoid some of the duplicate definition problems, we have a similar approach that was done with rl_gputex.h with function names, avoid the raylib structs, and just have the raylib API call the library's functions...

void rl_imagedrawpixel(void* data, int format, int width, int height,
        int posX, int posY,
        unsigned char colorR,
        unsigned char colorG,
        unsigned char colorB,
        unsigned char colorA);

void ImageDrawPixel(Image* dst, int posX, int posY, Color color) {
    rl_imagedrawpixel(dst->data, dst->format, dst->width, dst->height,
        posX, posY,
        color.r, color.g, color.b, color.a);
}

Avoiding the structs could make the function definitions extremely long in the library, but the benefit of not having to deal with the duplicate structs could be worth it.

[JeffM2501]

I'm not sure I'd call it a software rendering module. I'd call it Image Drawing, Software rendering makes it sound like it's a full blown 3d renderer on par with OpenGL, and it is not.

[RobLoach]

Good call, renamed the discussion. Definitely more image manipulation than rendering.

[raysan5]

Actually SDL calls the internal software renderer that same name despite only supporting 2d rendering...

[konsumer]

I think this idea is great. Drawing stuff on the screen is a bit complicated in libretro without this, but very familiar & easy with it.

[raysan5]

@RobLoach Definitely I want to do something on that line for a 2d-software-rendered or image-drawing functionality but I'm still thinking the best approach for it. My first idea was just keeping rtextures.c and enable pure image-rendeing with a flag, allowing the texture functions to fall-back to the image functions (#1370) but it increases the complexity of the module a lot, and it won't be a simple learning-material anymore for new users.

Moving the image functionality to a separate rimage.h it's probably the best approach but then we face the function duplicate issues and the coupling with raylib functionality, and again the complexity of the module is increased (probably not much for programmers with some experience but probably enough for novice programmers to avoid jumping and modifying it...)

I need to think about the best solution but definetly I want to allow it; I've got a side project to run raylib on RP2040 microcontroller (no-GPU, 264KB RAM) and I need the 2d-software-rendering option.

[RobLoach]

raylib on RP2040 microcontroller (no-GPU, 264KB RAM)

🤯 That's pretty awesome! Would be so cool to play some raylib games on a small handheld.

[raysan5]

It's on my TODO list, actually I started working on it about one year ago but too many things got in the middle this last year...