/mnt/nas/libepaper/include/epaper/io/image_io.hpp

// Load and display image
auto result = ImageIO::load_image("logo.png", 3);  // Force RGB
if (result) {
  auto [w, h, ch, data] = *result;
  // Convert RGB to framebuffer color mode
  for (size_t y = 0; y < h; ++y) {
    for (size_t x = 0; x < w; ++x) {
      size_t idx = (y * w + x) * 3;
      RGB rgb{data[idx], data[idx+1], data[idx+2]};
      Color c = ColorManager::to_color(rgb, DisplayMode::BlackWhite);
      framebuffer.set_pixel(x, y, c, Orientation::Portrait0);
    }
  }
}
 
// Save framebuffer as PNG
auto rgb = ImageIO::framebuffer_to_rgb(framebuffer);
ImageIO::save_png("output.png", fb.width(), fb.height(), 3, rgb);

See also

ColorManager, FramebufferLike, stb_image (third_party)

#pragma once
 
#include "epaper/color/color_manager.hpp"
#include "epaper/core/errors.hpp"
#include "epaper/core/framebuffer_concepts.hpp"
#include "epaper/core/types.hpp"
#include <cstddef>
#include <expected>
#include <span>
#include <string_view>
#include <vector>
 
namespace epaper {
 
class ImageIO {
public:
  struct ImageResult {
    std::size_t width;
    std::size_t height;
    std::size_t channels;
    std::vector<std::uint8_t> data; // Row-major, interleaved channels
  };
 
  [[nodiscard]] static auto load_image(std::string_view path, int desired_channels = 0)
      -> std::expected<ImageResult, Error>;
 
  [[nodiscard]] static auto save_png(std::string_view path, std::size_t width, std::size_t height, int channels,
                                     std::span<const std::uint8_t> data) -> std::expected<void, Error>;
 
  template <FramebufferLike FB> [[nodiscard]] static auto framebuffer_to_rgb(const FB &fb) -> std::vector<std::uint8_t>;
};
 
// ========== Template Implementation ==========
 
template <FramebufferLike FB> auto ImageIO::framebuffer_to_rgb(const FB &fb) -> std::vector<std::uint8_t> {
  std::size_t w = fb.width();
  std::size_t h = fb.height();
  std::vector<std::uint8_t> rgb;
  rgb.reserve(w * h * 3);
 
  for (std::size_t y = 0; y < h; ++y) {
    for (std::size_t x = 0; x < w; ++x) {
      Color c = fb.get_pixel(x, y, Orientation::Portrait0);
      auto rgb_val = ColorManager::to_rgb(c);
      rgb.push_back(rgb_val.r);
      rgb.push_back(rgb_val.g);
      rgb.push_back(rgb_val.b);
    }
  }
  return rgb;
}
 
} // namespace epaper