laurence
5286a2e81b
The scripts that processed the NGC 5128 session of 2026-07-21 previously lived inside the data directory and addressed it with absolute paths. Code and data are now separated: the code lives here, and a session is located at runtime through the ASTRO_SESSION environment variable. layout.py is what makes that work. It maps a FILENAME to the subdirectory that file belongs in, using the same rules the session directories are organised with, so a script can go on asking for 'master-Red.fit' or '_stars.npz' without any call site knowing the directory structure. Anything unrecognised resolves to the session root, which is visible and correctable rather than silently wrong. restructure.py reorganises a flat session directory into that layout. It is idempotent and dry-run by default. The 50 session scripts are kept as they were run rather than tidied into a library. They were written in sequence as the work went along, several of them by parallel agents, and they show it - but they are the honest provenance of a published set of results, and the productionised pipeline should be able to reproduce those results exactly. Verified before committing: all 51 files compile without warnings, and verify_core.py, closeup.py and triptych.py were run end to end against the reorganised session, correctly finding inputs across calibrated/, stacks/masters/ and final/ and writing outputs back to the right places.
102 lines
4.4 KiB
Python
102 lines
4.4 KiB
Python
"""Image 4: the close-up, framed by the galaxy's own measured extent.
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The crop box is not chosen by eye. The surface photometry produced an isophote
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model of NGC 5128, and the region where that model carries real signal defines
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how much sky the galaxy actually occupies; the frame is that region plus a
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margin. So "keeping the object in frame" is a measured statement rather than a
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judgement, and the same rule would frame any other galaxy without retuning.
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It is cut from image 3's 16-bit TIFF rather than from the PNG, and never
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resampled, so every pixel is exactly the pixel that came out of the pipeline.
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Re-rendering was considered and rejected: the stretch in image 3 is already
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anchored on sky statistics measured across the whole frame, and a tight crop
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contains too little empty sky to measure a better one. Cropping is therefore
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not a compromise here - it is the correct operation.
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"""
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import os
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import numpy as np
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import tifffile
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from astropy.io import fits
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from astropy.wcs import WCS
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from PIL import Image
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import layout
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OUT = layout.SESSION
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# The finished renderings live in their own directory: they are the
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# deliverables, and keeping them apart from the masters, the
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# intermediates and the analysis figures makes it obvious which
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# files are meant to be looked at.
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FINAL = layout.path("final")
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SOURCE = "NGC5128-final-3-best.tif"
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CROP = 48 # the border already removed from image 3
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MARGIN = 0.08 # sky margin around the galaxy, as a fraction
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MODEL_FLOOR = 5.0 # ADU/px: where the isophote model still has signal
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def main():
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model = fits.getdata(layout.path("sb-model.fits")).astype(np.float32)
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ys, xs = np.where(model > MODEL_FLOOR)
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# Model coordinates are on the uncropped grid; image 3 lost CROP px.
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x0, x1 = xs.min() - CROP, xs.max() - CROP
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y0, y1 = ys.min() - CROP, ys.max() - CROP
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print(f"galaxy extent (model > {MODEL_FLOOR} ADU/px): "
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f"x {x0}-{x1}, y {y0}-{y1} = {x1 - x0} x {y1 - y0} px")
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with fits.open(layout.path("master-Luminance.fit")) as hd:
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wcs = WCS(hd[0].header, naxis=2)
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img = tifffile.imread(layout.path(SOURCE))
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ny, nx = img.shape[:2]
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print(f"source {SOURCE}: {nx} x {ny}, {img.dtype}")
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# Centre the frame on the galaxy's own centre, not on the frame's.
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cx, cy = (x0 + x1) / 2.0, (y0 + y1) / 2.0
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half_x = (x1 - x0) / 2.0 * (1 + MARGIN)
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half_y = (y1 - y0) / 2.0 * (1 + MARGIN)
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# One box for both axes keeps the galaxy from touching a short edge, and a
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# round object in a near-square frame reads better than in a letterbox.
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half = max(half_x, half_y)
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# Clamp inside the image while keeping the galaxy centred as far as
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# possible; report honestly if the frame has to shrink.
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half = min(half, cx, cy, nx - cx, ny - cy)
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left, right = int(round(cx - half)), int(round(cx + half))
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top, bottom = int(round(cy - half)), int(round(cy + half))
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print(f"crop box x {left}-{right}, y {top}-{bottom} "
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f"({right - left} x {bottom - top} px)")
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# Verify the whole galaxy really is inside before writing anything.
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assert left <= x0 and right >= x1 and top <= y0 and bottom >= y1, \
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"galaxy would be clipped - refusing to write"
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inset_x = min(x0 - left, right - x1)
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inset_y = min(y0 - top, bottom - y1)
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print(f"clearance to the nearest edge: {inset_x} px horizontally, "
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f"{inset_y} px vertically")
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scale = 0.5376
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print(f"field of view {(right - left) * scale / 60:.1f}' x "
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f"{(bottom - top) * scale / 60:.1f}'")
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corner = wcs.pixel_to_world(left + CROP, top + CROP)
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centre = wcs.pixel_to_world((left + right) / 2 + CROP,
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(top + bottom) / 2 + CROP)
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print(f"frame centre {centre.to_string('hmsdms')}")
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print(f"top-left corner {corner.to_string('hmsdms')}")
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crop = img[top:bottom, left:right]
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tifffile.imwrite(layout.path("NGC5128-final-4-closeup.tif"), crop,
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photometric="rgb")
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u8 = (crop.astype(np.float32) / 65535.0 * 255 + 0.5).astype(np.uint8)
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Image.fromarray(u8).save(layout.path("NGC5128-final-4-closeup.png"))
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prev = Image.fromarray(u8)
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prev.thumbnail((2400, 2400), Image.LANCZOS)
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prev.save(layout.path("NGC5128-final-4-closeup-preview.jpg"),
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quality=93)
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print("wrote NGC5128-final-4-closeup.tif / .png / -preview.jpg")
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os.makedirs(FINAL, exist_ok=True)
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if __name__ == "__main__":
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main()
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