Fix emoji/wide-char palette proportions

Emoji, hieroglyphs, dominos, mahjong, playing cards, cuneiform,
alchemical, flora, and weather palettes use double-width characters
that display at 2x normal monospace width in browsers.

Fix: detect wide palettes and halve the render width with adjusted
aspect ratio (1.0 instead of 0.55) so the output maintains correct
image proportions regardless of character width.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

render.py

@@ -57,13 +57,24 @@ PALETTES = {
 
 MAX_GIF_FRAMES = 60
 
+# Palettes with double-width characters (emoji, CJK supplementary, etc.)
+WIDE_PALETTES = {
+    "emoji", "flora", "weather", "dominos", "mahjong", "playing",
+    "hieroglyph", "cuneiform", "alchemical",
+}
+
+
+def is_wide_palette(name: str) -> bool:
+    """Check if a palette uses double-width (emoji/supplementary) characters."""
+    return name in WIDE_PALETTES
+
 
 def get_luminance(r: int, g: int, b: int) -> float:
     """Perceived luminance (0-255)."""
     return 0.299 * r + 0.587 * g + 0.114 * b
 
 
-def _prepare_frame(img: Image.Image, width: int, bg: str) -> Image.Image:
+def _prepare_frame(img: Image.Image, width: int, bg: str, wide_chars: bool = False) -> Image.Image:
     """Composite alpha onto background and resize for rendering."""
     # Apply EXIF orientation (phone photos come rotated without this)
     img = ImageOps.exif_transpose(img)
@@ -72,12 +83,21 @@ def _prepare_frame(img: Image.Image, width: int, bg: str) -> Image.Image:
     background = Image.new("RGBA", img.size, bg_color)
     background.paste(img, mask=img.split()[3])
     img = background.convert("RGB")
-    # Monospace chars in browser: ~0.6 width-to-height ratio at font-size 8px, line-height 1.05
-    # So each char cell is roughly 4.8px wide x 8.4px tall → ratio 0.57
-    char_aspect = 0.55
+
+    if wide_chars:
+        # Emoji/wide chars are ~2x the width of normal monospace chars
+        # so halve the render width to maintain correct proportions,
+        # and use a squarer aspect since each char cell is nearly square
+        render_width = max(1, width // 2)
+        char_aspect = 1.0
+    else:
+        render_width = width
+        # Monospace chars: ~0.55 width-to-height ratio at 5px font, line-height 1.0
+        char_aspect = 0.55
+
     aspect = img.height / img.width
-    height = max(1, int(width * aspect * char_aspect))
-    return img.resize((width, height), Image.LANCZOS)
+    height = max(1, int(render_width * aspect * char_aspect))
+    return img.resize((render_width, height), Image.LANCZOS)
 
 
 def _floyd_steinberg_dither(pixels: list[list[float]], width: int, height: int, levels: int) -> list[list[float]]:
@@ -192,7 +212,8 @@ def image_to_art(
 ) -> str:
     """Convert a static image to colorful Unicode art."""
     img = Image.open(image_path)
-    img = _prepare_frame(img, width, bg)
+    wide = is_wide_palette(palette_name)
+    img = _prepare_frame(img, width, bg, wide_chars=wide)
     chars = PALETTES.get(palette_name, PALETTES["wingdings"])
     return _render_frame(img, chars, double_width, dither, output_format)
 
@@ -208,6 +229,7 @@ def gif_to_art(
 ) -> list[dict]:
     """Convert an animated GIF to a list of frame dicts with art and duration."""
     img = Image.open(image_path)
+    wide = is_wide_palette(palette_name)
     chars = PALETTES.get(palette_name, PALETTES["wingdings"])
 
     frames = []
@@ -221,7 +243,7 @@ def gif_to_art(
 
     for frame in frame_list:
         duration = frame.info.get("duration", 100)
-        prepared = _prepare_frame(frame.copy(), width, bg)
+        prepared = _prepare_frame(frame.copy(), width, bg, wide_chars=wide)
         art = _render_frame(prepared, chars, double_width, dither, output_format)
         frames.append({"art": art, "duration": max(duration, 20)})
 
@@ -238,7 +260,8 @@ def render_from_pil(
     output_format: str = "ansi",
 ) -> str:
     """Render from a PIL Image object directly."""
-    prepared = _prepare_frame(img, width, bg)
+    wide = is_wide_palette(palette_name)
+    prepared = _prepare_frame(img, width, bg, wide_chars=wide)
     chars = PALETTES.get(palette_name, PALETTES["wingdings"])
     return _render_frame(prepared, chars, double_width, dither, output_format)