sol2_test/src/image.cpp

#include "image.hpp"
#include <stb_image.h>

unsigned int image_to_texture(unsigned char *data, int width, int height, int nrComponents) {
  unsigned int textureID;
  glGenTextures(1, &textureID);

  GLenum format = GL_RGB;

  switch(nrComponents) {
    case 1:
      format = GL_RED;
      break;
    case 3:
      format = GL_RGB;
      break;
    case 4:
      format = GL_RGBA;
      break;
    default:
      dbc::sentinel($F("Impossible nrComponents={} when loading image", nrComponents));
  }

  glBindTexture(GL_TEXTURE_2D, textureID);
  glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

  return textureID;
}

void Image::load(Node& node) {
  dbc::check(node.type == NodeType::IMAGE, "That's not an image idiot.");

  if(!node.config.contains("_image_data")) {
    dbc::check(node.config.contains("src"), "Node doesn't have an image src.");
    std::string filename = std::any_cast<std::string>(node.config.at("src"));

    int width = 0;
    int height = 0;
    int nrComponents = 0;
    stbi_set_flip_vertically_on_load(true);
    unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
    dbc::check(data != NULL, "Failed to stb_load image.");

    unsigned int texture_id = image_to_texture(data, width, height, nrComponents);

    node.config.try_emplace("_image_data", texture_id);

    stbi_image_free(data);
  }
}

void Image::render(Node& node, float xpos, float ypos, float w, float h) {
  dbc::check(node.config.contains("_image_data"), "Node isn't configured for images, did you Image::load?");

  unsigned int texture_id = std::any_cast<unsigned int>(node.config.at("_image_data"));

  shader.use();
  shader.setInt("texture1", texture_id);
  glBindVertexArray(image_vao);
  glBindTexture(GL_TEXTURE_2D, texture_id);
  glDrawArrays(GL_TRIANGLES, 0, 6);
}

Image::Image() {
  glGenVertexArrays(1, &image_vao);
  glGenBuffers(1, &image_vbo);

  glBindVertexArray(image_vao);
  glBindBuffer(GL_ARRAY_BUFFER, image_vbo);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), &vertices, GL_STATIC_DRAW);

  // position attrib
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
  glEnableVertexAttribArray(0);

  // color attribute
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2 * sizeof(float)));
  glEnableVertexAttribArray(1);
}