Jungfraujoch/reader/MarCCD.h

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

#pragma once

#include <cstdint>
#include <string>
#include <vector>

// marCCD: an ordinary uncompressed TIFF whose 3072-byte instrument header sits in the gap between
// the TIFF header and the pixels. The image is read through libtiff, which the build already
// carries; the instrument header is a fixed-offset block of little-endian int32, so it is read
// directly. Rayonix MX-series and mar Mosaic detectors both write it, under half a dozen file
// extensions (.mccd, .img, .tif, or a bare frame number).
//
// Every value the header stores is an integer times a fixed scale: lengths in micrometres or
// nanometres, angles in millidegrees, the wavelength in 1e-5 A. They are converted here, so the
// rest of the code sees metres, degrees and angstroms like every other reader.
namespace marccd {

// Byte offset of the instrument header when the file does not say. Every writer seen puts it here
// and states it in TIFF tag 34710 as well.
inline constexpr uint32_t DEFAULT_HEADER_OFFSET = 1024;

// The private TIFF tag in which marCCD states where its own header begins.
inline constexpr uint16_t TIFFTAG_MARCCD_HEADER_OFFSET = 34710;

struct Header {
    std::string detector;            // from the TIFF Model/Software tags where they say anything
    int64_t nx = 0;                  // fast dimension (columns)
    int64_t ny = 0;                  // slow dimension (rows)
    double pixel_x_m = 0;
    double pixel_y_m = 0;
    double distance_m = 0;
    double beam_x_px = 0;
    double beam_y_px = 0;
    double wavelength_A = 0;
    double start_angle_deg = 0;
    double angle_increment_deg = 0;
    double two_theta_deg = 0;
    double exposure_s = 0;
    int64_t saturated_value = 0;
    std::string axis_name = "phi";   // the circle that moved between start and end
};

// True if the path names something this reader can open: a marCCD file, or a directory holding at
// least one. Reads a few kB at most.
bool CanRead(const std::string &path);

// The files of one sweep, in collection order. path is a directory, or one frame inside the sweep
// to take the whole sweep from. Empty where there is none.
std::vector<std::string> CollectSweep(const std::string &path);

// Header only - reads the first few kB of the file. Cheap enough to call per frame for the
// rotation angles.
Header ReadHeader(const std::string &path);

// Header + pixels of one file. out is resized to nx * ny.
Header Read(const std::string &path, std::vector<int32_t> &out);

// The same, widening the stored uint16 into memory the caller already has. scratch carries the
// 16-bit strip between frames, so a worker walking a sweep allocates once. Throws if the image
// does not fit in capacity pixels.
Header ReadInto(const std::string &path, int32_t *out, size_t capacity, std::vector<uint8_t> &scratch);

}  // namespace marccd