Working Python version for Commodore.

c64view/imageprep.py

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+"""Load a modern image and prepare it for a given C64 display mode.
+
+The output is always a plain HxWx3 uint8 sRGB numpy array sized to the mode's
+*logical* pixel grid (e.g. 160x200 for multicolor, 320x200 for hires).  The 2:1
+multicolor pixel aspect is handled here so the source image is never visually
+squashed: we resize to the displayed shape and then sub-sample to the logical
+grid, which keeps circles round.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+import numpy as np
+from PIL import Image, ImageEnhance, ImageOps
+
+
+@dataclass
+class PrepOptions:
+    aspect: str = "fit"          # "fit" (letterbox), "fill" (crop), "stretch"
+    brightness: float = 1.0      # 1.0 = unchanged
+    contrast: float = 1.0
+    saturation: float = 1.0
+    gamma: float = 1.0           # <1 brightens midtones, >1 darkens
+    border_index: int = 0        # palette index used for letterbox bars
+
+
+def _apply_enhancements(img: Image.Image, opt: PrepOptions) -> Image.Image:
+    if opt.brightness != 1.0:
+        img = ImageEnhance.Brightness(img).enhance(opt.brightness)
+    if opt.contrast != 1.0:
+        img = ImageEnhance.Contrast(img).enhance(opt.contrast)
+    if opt.saturation != 1.0:
+        img = ImageEnhance.Color(img).enhance(opt.saturation)
+    if opt.gamma != 1.0:
+        lut = [min(255, int((i / 255.0) ** opt.gamma * 255 + 0.5)) for i in range(256)]
+        img = img.point(lut * 3)
+    return img
+
+
+def prepare(
+    path_or_img,
+    logical_w: int,
+    logical_h: int,
+    pixel_aspect: float,
+    opt: PrepOptions,
+    border_rgb=(0, 0, 0),
+) -> np.ndarray:
+    """Return an (logical_h, logical_w, 3) uint8 sRGB array.
+
+    ``pixel_aspect`` is width/height of one logical pixel on screen (2.0 for
+    multicolor, 1.0 for hires).  ``border_rgb`` fills letterbox bars for "fit".
+    """
+    if isinstance(path_or_img, Image.Image):
+        img = path_or_img
+    else:
+        img = Image.open(path_or_img)
+    img = ImageOps.exif_transpose(img).convert("RGB")
+    img = _apply_enhancements(img, opt)
+
+    # Displayed target shape (square display pixels): the logical grid stretched
+    # by the pixel aspect ratio horizontally.
+    disp_w = int(round(logical_w * pixel_aspect))
+    disp_h = logical_h
+
+    if opt.aspect == "stretch":
+        fitted = img.resize((disp_w, disp_h), Image.LANCZOS)
+    elif opt.aspect == "fill":
+        fitted = ImageOps.fit(img, (disp_w, disp_h), Image.LANCZOS, centering=(0.5, 0.5))
+    else:  # "fit" -> letterbox
+        scaled = img.copy()
+        scaled.thumbnail((disp_w, disp_h), Image.LANCZOS)
+        fitted = Image.new("RGB", (disp_w, disp_h), tuple(int(c) for c in border_rgb))
+        fitted.paste(scaled, ((disp_w - scaled.width) // 2, (disp_h - scaled.height) // 2))
+
+    # Collapse displayed shape back to the logical grid (undo the aspect stretch).
+    logical = fitted.resize((logical_w, logical_h), Image.LANCZOS)
+    return np.asarray(logical, dtype=np.uint8)