Jungfraujoch/common/AssembleToPlane.h

// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <algorithm>
#include <cmath>
#include <cstdint>
#include <vector>

#include "DetectorModules.h"

// The detector plane as a picture: raster pixel (i, j) is the plane point (x0 + i, y0 + j). For the
// algorithms that need the detector as it really is - a beam-stop shadow and the gaps it crosses, the point
// symmetry about the beam, a picture of the detector - and not as the panels are stored.
struct PlaneRaster {
    int64_t x0 = 0, y0 = 0, width = 0, height = 0;
};

// The raster holding every panel. It starts at the plane origin, so plane and raster coordinates agree,
// unless a panel lies left of or above it. Empty table: the image itself.
PlaneRaster PlaneRasterOf(const DetectorModules &modules, int64_t width, int64_t height);

// The image (width x height) as the plane raster: each raster pixel takes the image pixel nearest its centre
// on the panel it falls on, and `gap` where it falls on none. Empty table, with the image's own raster: a copy.
template<class T>
std::vector<T> AssembleToPlane(const DetectorModules &modules, const std::vector<T> &image,
                               int64_t width, int64_t height, const PlaneRaster &raster, T gap) {
    std::vector<T> out(static_cast<size_t>(raster.width * raster.height), gap);
    const auto put = [&](const DetectorModule &m, int64_t i0, int64_t i1, int64_t j0, int64_t j1) {
        for (int64_t j = std::max<int64_t>(j0, 0); j < std::min(j1, raster.height); j++)
            for (int64_t i = std::max<int64_t>(i0, 0); i < std::min(i1, raster.width); i++) {
                const auto [x, y] = m.PlaneToImage(static_cast<double>(raster.x0 + i),
                                                   static_cast<double>(raster.y0 + j));
                if (m.ContainsImagePixel(x, y))
                    out[j * raster.width + i] = image[static_cast<size_t>(std::floor(y + 0.5)) * width
                                                      + static_cast<size_t>(std::floor(x + 0.5))];
            }
    };
    if (modules.empty()) {
        put(DetectorModule::AsImaged(0, 0, width, height), -raster.x0, width - raster.x0, -raster.y0,
            height - raster.y0);
        return out;
    }
    // Panel by panel, over the raster pixels of its footprint's box. Panels do not overlap.
    for (const auto &m: modules.Get()) {
        const PlaneBox box = DetectorModules({m}).PlaneBounds(width, height);
        put(m, static_cast<int64_t>(std::floor(box.x0)) - raster.x0, static_cast<int64_t>(std::ceil(box.x1)) - raster.x0,
            static_cast<int64_t>(std::floor(box.y0)) - raster.y0, static_cast<int64_t>(std::ceil(box.y1)) - raster.y0);
    }
    return out;
}

// The reverse, for a result computed on the raster: each image pixel on a panel takes the raster pixel
// nearest its centre on the plane, `outside` where that is off the raster; a pixel on no panel (a gap)
// is `outside` too. Empty table, with the image's own raster: a copy.
template<class T>
std::vector<T> GatherFromPlane(const DetectorModules &modules, const std::vector<T> &plane,
                               const PlaneRaster &raster, int64_t width, int64_t height, T outside) {
    std::vector<T> out(static_cast<size_t>(width * height), outside);
    modules.ForEachPixel(width, height, [&](int64_t, size_t index, double px, double py) {
        const auto i = static_cast<int64_t>(std::floor(px + 0.5)) - raster.x0;
        const auto j = static_cast<int64_t>(std::floor(py + 0.5)) - raster.y0;
        if (i >= 0 && i < raster.width && j >= 0 && j < raster.height)
            out[index] = plane[j * raster.width + i];
    });
    return out;
}