Spectrum comparison

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Spectrum comparison (visual overlay)

Available since v4.10.0 · Menu File → Compare spectrum…

Modules: gui/file_actions.py (on_open_comparison, on_clear_comparison), gui/canvas.py (render), gui/plotly_tools.py, gui/state.py (ComparisonSpectrum)

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What it does

Allows loading one or more additional spectra and overlaying them on the main spectrum as thin lines of distinct colors, without touching the fit engine or the calibration state. It is a purely visual aid to compare samples, follow a temperature series at a glance, or contrast a spectrum with a reference.

• Up to 6 comparison spectra simultaneously.
• Each one with a distinct color from the palette: orange, teal, pink, lime, violet, sky blue.
• They also appear in the exportable Plotly figure (interactive HTML).
• Fitting keeps working with comparison spectra active: they do not interfere.

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Usage flow

1. First load a main spectrum (File → Load…). Without a main spectrum, "Compare spectrum…" shows a warning and does nothing.
2. File → Compare spectrum… → select an ADT/WS5/CSV file.
3. The spectrum is normalized and overlaid (first line: orange).
4. Repeat to add more (second: teal, etc.), up to 6.
5. File → Clear comparison removes all (the action is enabled only when there is at least one).

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Loading and normalization

on_open_comparison accepts the same formats as the main spectrum:

Format	Treatment
.csv, .txt, .dat, .exp	load_velocity_csv — already folded in velocity
.ws5, .adt	Automatic folding: find_best_integer_or_half_center + fold_and_normalize with the optimal center, axis by velocity_axis

After loading, the spectrum is normalized to relative transmission (baseline ≈ 1.0) by dividing by the 90th percentile:

norm = float(np.percentile(y_raw, 90)) or 1.0
y_data = y_raw / norm

The result is stored as a ComparisonSpectrum:

@dataclass
class ComparisonSpectrum:
    """Espectro cargado solo para comparación visual (sin ajuste)."""
    path: Path
    velocity: np.ndarray
    y_data: np.ndarray
    label: str

and is added to self.comparison_spectra (list initialized in __init__ of MossbauerQtWindow). The label is the file name without extension.

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Rendering

Matplotlib canvas (gui/canvas.py)

render() accepts a comparison= parameter (list of ComparisonSpectrum). The comparison lines are drawn before the main spectrum, with the _COMPARISON_PALETTE palette. They are stored in self._artists["cmp_lines"] and the layout signature (layout_sig) includes n_cmp = len(comparison) to force a full redraw when the number of compared spectra changes.

Plotly (gui/plotly_tools.py)

Each comparison spectrum is added as a Scattergl trace (lines, opacity 0.75) before the main spectrum trace, with its palette color, so that it also appears in the interactive HTML export.

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Separation of responsibilities

• The ComparisonSpectrum are display-only: they do not enter FitState, are not saved in the session, do not affect the calibration or the model.
• on_clear_comparison empties the list and disables the clear action.
• The rescaling of each spectrum is independent (its own 90th percentile), so that spectra with different absorption depth are compared on the same relative transmission scale.

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Translation strings

The menu labels and messages are in locales/{es,en,fr}/strings.json:

• file.compare_spectrum, file.clear_comparison
• status.comparison_added, status.comparison_cleared
• msg.comparison_needs_main