Astronomical imaging,
programmable.

#include <syq/syq.h>
#include <algorithm>
#include <cstdint>
#include <vector>

syq::Reader reader("M31.syq");
const syq::Image image = reader.image();     // primary image when id is omitted
const uint64_t nx = (image.width  + image.tileSize - 1) / image.tileSize;
const uint64_t ny = (image.height + image.tileSize - 1) / image.tileSize;

// Destination layout in this example: channel-planar Float64.
std::vector<double> pixels(image.width * image.height * image.channels);
for (uint64_t ty = 0; ty < ny; ++ty) {
  for (uint64_t tx = 0; tx < nx; ++tx) {
    const uint64_t tileIndex = ty * nx + tx; // tiles are row-major
    const uint32_t w = std::min<uint64_t>(image.tileSize, image.width  - tx * image.tileSize);
    const uint32_t h = std::min<uint64_t>(image.tileSize, image.height - ty * image.tileSize);
    const auto raw = reader.readTile(image, tileIndex); // verifies SHA-256 and decompresses
    const auto tile = syq::decodeSamples(raw, image.sample);

    for (uint32_t c = 0; c < image.channels; ++c)
      for (uint32_t y = 0; y < h; ++y)
        for (uint32_t x = 0; x < w; ++x) {
          const auto source = (uint64_t(c) * h + y) * w + x;
          const auto target = (uint64_t(c) * image.height + ty * image.tileSize + y)
                            * image.width + tx * image.tileSize + x;
          pixels[target] = tile[source];
        }
  }
}

syq::Image image;
image.width = width; image.height = height; image.channels = channels;
image.tileSize = 256;
image.sample = syq::Sample::Float32;
image.role = "MAIN_IMAGE";
image.transfer = "LINEAR";
image.state = "PROCESSED_LINEAR";
image.metadata.insert(QStringLiteral("syq.camera.model"), QStringLiteral("Example Camera"));

syq::Writer writer("result.syq");           // atomic replacement
const auto primary = writer.addImage(image,
  [&](uint64_t x0, uint64_t y0, uint32_t w, uint32_t h) {
    std::vector<double> tile(uint64_t(w) * h * channels);
    // sourcePixels and each tile are channel-planar: [all R][all G][all B].
    for (uint32_t c = 0; c < channels; ++c)
      for (uint32_t y = 0; y < h; ++y)
        for (uint32_t x = 0; x < w; ++x)
          tile[(uint64_t(c) * h + y) * w + x] =
            sourcePixels[(uint64_t(c) * height + y0 + y) * width + x0 + x];
    return syq::encodeSamples(tile, image.sample);
  });
writer.commit(primary);                      // publishes directory + recovery footer

// Append metadata without rewriting the image payload.
syq::Reader existing("result.syq");
syq::Writer transaction("result.syq", true);
QCborMap note{{QStringLiteral("vendor.example.reviewed"), true}};
transaction.add(syq::Type::Metadata, QCborValue(note).toCbor());
transaction.commit(existing.primaryId());