feat: add image-color-correction

image-color-correction/warm_print.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+# /// script
+# requires-python = ">=3.12"
+# dependencies = [
+#   "numpy==2.5.2",
+#   "pillow==12.3.0",
+# ]
+# ///
+"""
+Apply a warm print color correction (less blue, slightly yellower).
+
+Usage with uv (no venv, no uv pip):
+    uv run warm_print.py /path/to/image.jpg
+
+uv reads the dependencies in the header above and installs them
+into an isolated cache on first run.
+
+Writes next to the source, same basename + "_warmprint", same extension.
+Example: photo.jpg -> photo_warmprint.jpg
+"""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+import numpy as np
+from PIL import Image, ImageEnhance
+
+
+def warm_correct(im: Image.Image) -> Image.Image:
+    """Shift RGB toward warm/yellow while keeping brightness similar.
+
+    Matches the correction used for the preview print file:
+    lift red, lift green a little, cut blue, extra midtone warmth,
+    then a small contrast/saturation polish.
+    """
+    # Work in linear-ish 0..1 float. Source may be RGB or RGBA; color
+    # math is on RGB only. Alpha is copied back unchanged if present.
+    rgba = im.mode == "RGBA"
+    if rgba:
+        alpha = np.asarray(im.getchannel("A"))
+    rgb = im.convert("RGB")
+    arr = np.asarray(rgb).astype(np.float32) / 255.0
+    r, g, b = arr[..., 0], arr[..., 1], arr[..., 2]
+
+    # Rec. 709 luma — used so we can warm the hue without crushing
+    # or blowing overall brightness (prints already look darker).
+    luma = 0.2126 * r + 0.7152 * g + 0.0722 * b
+
+    # Global channel remap: more red, a bit more green, much less blue.
+    # That combination reads as yellow/warm rather than magenta or green.
+    r2 = r * 1.10 + 0.018
+    g2 = g * 1.045 + 0.010
+    b2 = b * 0.82 - 0.008
+
+    # Stronger warmth in midtones (skin, white fabric). Highlights and
+    # shadows get less so whites don't go mustard and blacks stay clean.
+    mid = np.clip(1.0 - np.abs(luma - 0.55) / 0.55, 0.0, 1.0)
+    r2 = r2 + 0.025 * mid
+    g2 = g2 + 0.018 * mid
+    b2 = b2 - 0.012 * mid
+
+    new = np.stack([r2, g2, b2], axis=-1)
+
+    # Re-match original luma, then add a tiny lift (prints look darker
+    # than screens). Clamp the scale so clipped/near-black pixels stay sane.
+    new_luma = 0.2126 * new[..., 0] + 0.7152 * new[..., 1] + 0.0722 * new[..., 2]
+    target = luma * 1.03 + 0.01
+    scale = np.where(new_luma > 1e-4, target / new_luma, 1.0)
+    scale = np.clip(scale, 0.85, 1.18)
+    new = np.clip(new * scale[..., None], 0.0, 1.0)
+
+    out_im = Image.fromarray((new * 255.0 + 0.5).astype(np.uint8), mode="RGB")
+
+    # Small polish after the hue shift so it doesn't look flat.
+    out_im = ImageEnhance.Contrast(out_im).enhance(1.04)
+    out_im = ImageEnhance.Color(out_im).enhance(1.06)
+
+    if rgba:
+        out_im = out_im.convert("RGBA")
+        out_im.putalpha(Image.fromarray(alpha))
+    return out_im
+
+
+def main() -> int:
+    if len(sys.argv) < 2:
+        print("Usage: python warm_print.py /path/to/image.jpg", file=sys.stderr)
+        return 2
+
+    src = Path(sys.argv[1]).expanduser().resolve()
+    if not src.is_file():
+        print(f"Not a file: {src}", file=sys.stderr)
+        return 1
+
+    # Same folder, same name, short suffix before the original extension.
+    dest = src.with_name(f"{src.stem}_warmprint{src.suffix}")
+
+    im = Image.open(src)
+    # Keep ICC if the source had one so color-managed printers stay consistent.
+    icc = im.info.get("icc_profile")
+    out_im = warm_correct(im)
+
+    ext = src.suffix.lower()
+    save_kwargs: dict = {"optimize": True}
+    if icc:
+        save_kwargs["icc_profile"] = icc
+    if ext in {".jpg", ".jpeg"}:
+        # High-quality JPEG for print; 4:4:4 so chroma isn't smeared.
+        save_kwargs.update(quality=95, subsampling=0)
+        out_im = out_im.convert("RGB")
+        out_im.save(dest, "JPEG", **save_kwargs)
+    else:
+        out_im.save(dest, "PNG", **save_kwargs)
+    print(dest)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())