Image ports

Supported bindings: ossia

Some media systems have the ability to process images. Avendish is not restricted here :-)

Note that this part of the system is still pretty much in flux, in particular with regards of how allocations are supposed to be handled. Any feedback on this is welcome.

First, here is how we define a viable texture type:

struct my_texture
  enum format { RGBA }; // The only recognized one so far
  unsigned char* bytes;
  int width;
  int height;
  bool changed;

Then, a texture port:

struct {
  rgba_texture texture;
} input;

Note that currently, it is the responsibility of the plug-in author to allocate the texture and set the changed bool for output ports. Input textures come from outside.

Due to the large cost of uploading a texture, changed is used to indicate both to the plug-in author that input textures have been touched,and for the plug-in author to indicate to the external environment that the output has changed and must be re-uploaded to the GPU.

GPU processing

Check the Writing GPU Processors chapter of this book!


A few types are provided:

  • halp::rgba_texture
  • halp::texture_input<"Name"> provides methods to get an RGBA pixel:
auto [r,g,b,a] = tex.get(10, 20);
  • halp::texture_output<"Name"> provides methods to set a RGBA pixel:
tex.set(10, 20, {.r = 10, .g = 100, .b = 34, .a = 255});
tex.set(10, 20, 10, 100, 34, 255);

as well as useful method to initialize and mark the texture ready for upload:

// Call this in the constructor or before processing starts
tex.create(100, 100);

// Call this after making changes to the texture