1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
|
"""Book cover generation: stdlib-only PNG with gradient + title text.
Covers are a vertical gradient between two random light colors with the
book title rendered on top in white with a black outline and a drop
shadow, using an embedded 5x7 bitmap font. No third-party image libraries
are required: PNG scanlines are packed and compressed with zlib/struct
directly.
"""
import logging
import random
import struct
import zlib
from colorsys import hsv_to_rgb
from pathlib import Path
from typing import List, Optional, Tuple
logger = logging.getLogger(__name__)
COVER_WIDTH = 600
COVER_HEIGHT = 900
# 5x7 bitmap font for ASCII 32..126. Each glyph is 7 rows of 5 bits
# (MSB left), encoded as ints for compactness.
_FONT = {
" ": [0, 0, 0, 0, 0, 0, 0],
"!": [0x04, 0x04, 0x04, 0x04, 0x04, 0x00, 0x04],
'"': [0x0A, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00],
"#": [0x0A, 0x0A, 0x1F, 0x0A, 0x1F, 0x0A, 0x0A],
"$": [0x04, 0x0F, 0x14, 0x0E, 0x05, 0x1E, 0x04],
"%": [0x18, 0x19, 0x02, 0x04, 0x08, 0x13, 0x03],
"&": [0x08, 0x14, 0x14, 0x08, 0x15, 0x12, 0x0D],
"'": [0x04, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00],
"(": [0x02, 0x04, 0x08, 0x08, 0x08, 0x04, 0x02],
")": [0x08, 0x04, 0x02, 0x02, 0x02, 0x04, 0x08],
"*": [0x00, 0x04, 0x15, 0x0E, 0x15, 0x04, 0x00],
"+": [0x00, 0x04, 0x04, 0x1F, 0x04, 0x04, 0x00],
",": [0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x08],
"-": [0x00, 0x00, 0x00, 0x1F, 0x00, 0x00, 0x00],
".": [0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x0C],
"/": [0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x00],
"0": [0x0E, 0x11, 0x13, 0x15, 0x19, 0x11, 0x0E],
"1": [0x04, 0x0C, 0x04, 0x04, 0x04, 0x04, 0x0E],
"2": [0x0E, 0x11, 0x01, 0x02, 0x04, 0x08, 0x1F],
"3": [0x1F, 0x02, 0x04, 0x02, 0x01, 0x11, 0x0E],
"4": [0x02, 0x06, 0x0A, 0x12, 0x1F, 0x02, 0x02],
"5": [0x1F, 0x10, 0x1E, 0x01, 0x01, 0x11, 0x0E],
"6": [0x06, 0x08, 0x10, 0x1E, 0x11, 0x11, 0x0E],
"7": [0x1F, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08],
"8": [0x0E, 0x11, 0x11, 0x0E, 0x11, 0x11, 0x0E],
"9": [0x0E, 0x11, 0x11, 0x0F, 0x01, 0x02, 0x0C],
":": [0x00, 0x0C, 0x0C, 0x00, 0x0C, 0x0C, 0x00],
";": [0x00, 0x0C, 0x0C, 0x00, 0x0C, 0x04, 0x08],
"<": [0x02, 0x04, 0x08, 0x10, 0x08, 0x04, 0x02],
"=": [0x00, 0x00, 0x1F, 0x00, 0x1F, 0x00, 0x00],
">": [0x08, 0x04, 0x02, 0x01, 0x02, 0x04, 0x08],
"?": [0x0E, 0x11, 0x01, 0x02, 0x04, 0x00, 0x04],
"@": [0x0E, 0x11, 0x17, 0x15, 0x17, 0x10, 0x0E],
"A": [0x0E, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11],
"B": [0x1E, 0x11, 0x11, 0x1E, 0x11, 0x11, 0x1E],
"C": [0x0E, 0x11, 0x10, 0x10, 0x10, 0x11, 0x0E],
"D": [0x1C, 0x12, 0x11, 0x11, 0x11, 0x12, 0x1C],
"E": [0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x1F],
"F": [0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x10],
"G": [0x0E, 0x11, 0x10, 0x17, 0x11, 0x11, 0x0F],
"H": [0x11, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11],
"I": [0x0E, 0x04, 0x04, 0x04, 0x04, 0x04, 0x0E],
"J": [0x01, 0x01, 0x01, 0x01, 0x01, 0x11, 0x0E],
"K": [0x11, 0x12, 0x14, 0x18, 0x14, 0x12, 0x11],
"L": [0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x1F],
"M": [0x11, 0x1B, 0x15, 0x15, 0x11, 0x11, 0x11],
"N": [0x11, 0x19, 0x15, 0x13, 0x11, 0x11, 0x11],
"O": [0x0E, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E],
"P": [0x1E, 0x11, 0x11, 0x1E, 0x10, 0x10, 0x10],
"Q": [0x0E, 0x11, 0x11, 0x11, 0x15, 0x12, 0x0D],
"R": [0x1E, 0x11, 0x11, 0x1E, 0x14, 0x12, 0x11],
"S": [0x0F, 0x10, 0x10, 0x0E, 0x01, 0x01, 0x1E],
"T": [0x1F, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04],
"U": [0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E],
"V": [0x11, 0x11, 0x11, 0x11, 0x11, 0x0A, 0x04],
"W": [0x11, 0x11, 0x11, 0x15, 0x15, 0x15, 0x0A],
"X": [0x11, 0x11, 0x0A, 0x04, 0x0A, 0x11, 0x11],
"Y": [0x11, 0x11, 0x0A, 0x04, 0x04, 0x04, 0x04],
"Z": [0x1F, 0x01, 0x02, 0x04, 0x08, 0x10, 0x1F],
"[": [0x0E, 0x08, 0x08, 0x08, 0x08, 0x08, 0x0E],
"\\": [0x00, 0x10, 0x08, 0x04, 0x02, 0x01, 0x00],
"]": [0x0E, 0x02, 0x02, 0x02, 0x02, 0x02, 0x0E],
"^": [0x04, 0x0A, 0x11, 0x00, 0x00, 0x00, 0x00],
"_": [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1F],
"`": [0x08, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00],
"a": [0x00, 0x00, 0x0E, 0x01, 0x0F, 0x11, 0x0F],
"b": [0x10, 0x10, 0x1E, 0x11, 0x11, 0x11, 0x1E],
"c": [0x00, 0x00, 0x0F, 0x10, 0x10, 0x10, 0x0F],
"d": [0x01, 0x01, 0x0F, 0x11, 0x11, 0x11, 0x0F],
"e": [0x00, 0x00, 0x0E, 0x11, 0x1F, 0x10, 0x0E],
"f": [0x06, 0x08, 0x1E, 0x08, 0x08, 0x08, 0x08],
"g": [0x00, 0x0F, 0x11, 0x11, 0x0F, 0x01, 0x1E],
"h": [0x10, 0x10, 0x1E, 0x11, 0x11, 0x11, 0x11],
"i": [0x04, 0x00, 0x0C, 0x04, 0x04, 0x04, 0x0E],
"j": [0x02, 0x00, 0x06, 0x02, 0x02, 0x12, 0x0C],
"k": [0x10, 0x10, 0x12, 0x14, 0x18, 0x14, 0x12],
"l": [0x0C, 0x04, 0x04, 0x04, 0x04, 0x04, 0x0E],
"m": [0x00, 0x00, 0x1A, 0x15, 0x15, 0x15, 0x15],
"n": [0x00, 0x00, 0x1E, 0x11, 0x11, 0x11, 0x11],
"o": [0x00, 0x00, 0x0E, 0x11, 0x11, 0x11, 0x0E],
"p": [0x00, 0x00, 0x1E, 0x11, 0x11, 0x1E, 0x10],
"q": [0x00, 0x00, 0x0F, 0x11, 0x11, 0x0F, 0x01],
"r": [0x00, 0x00, 0x16, 0x09, 0x08, 0x08, 0x08],
"s": [0x00, 0x00, 0x0F, 0x10, 0x0E, 0x01, 0x1E],
"t": [0x08, 0x08, 0x1E, 0x08, 0x08, 0x08, 0x06],
"u": [0x00, 0x00, 0x11, 0x11, 0x11, 0x13, 0x0D],
"v": [0x00, 0x00, 0x11, 0x11, 0x11, 0x0A, 0x04],
"w": [0x00, 0x00, 0x11, 0x15, 0x15, 0x15, 0x0A],
"x": [0x00, 0x00, 0x11, 0x0A, 0x04, 0x0A, 0x11],
"y": [0x00, 0x00, 0x11, 0x11, 0x0F, 0x01, 0x1E],
"z": [0x00, 0x00, 0x1F, 0x02, 0x04, 0x08, 0x1F],
"{": [0x06, 0x08, 0x08, 0x04, 0x08, 0x08, 0x06],
"|": [0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04],
"}": [0x0C, 0x02, 0x02, 0x04, 0x02, 0x02, 0x0C],
"~": [0x00, 0x00, 0x08, 0x15, 0x02, 0x00, 0x00],
}
_GLYPH_WIDTH = 5
_GLYPH_HEIGHT = 7
# Any character outside the embedded font (accented letters, CJK,
# Cyrillic, ...) renders as an empty box: silently dropping it would
# blank those titles while still counting their width for centering.
_UNKNOWN_GLYPH = [0x1F, 0x11, 0x11, 0x11, 0x11, 0x11, 0x1F]
_TEXT_SCALE = 6 # render each font pixel as a 6x6 block
_TEXT_MARGIN = 60 # horizontal padding when wrapping
_TEXT_COLOR = (255, 255, 255)
_STROKE_COLOR = (0, 0, 0)
_STROKE_WIDTH = 3 # outline thickness in pixels
_SHADOW_OFFSET = 4 # drop shadow shift in pixels (down-right)
_SHADOW_DARKEN = 0.55 # shadow keeps 55% of the background color
def _random_light_color(rng: random.Random) -> Tuple[int, int, int]:
"""A random pastel: any hue, low saturation, high value."""
hue = rng.random()
saturation = rng.uniform(0.25, 0.55)
value = rng.uniform(0.82, 0.95)
r, g, b = hsv_to_rgb(hue, saturation, value)
return int(r * 255), int(g * 255), int(b * 255)
def _lerp(a: int, b: int, t: float) -> int:
return int(round(a + (b - a) * t))
def _text_width(text: str) -> int:
"""Pixel width of ``text`` at the rendered scale (spaces count too)."""
if not text:
return 0
return (len(text) * (_GLYPH_WIDTH + 1) - 1) * _TEXT_SCALE
def _wrap_title(title: str, max_width: int) -> List[str]:
"""Word-wrap ``title`` into lines that fit ``max_width`` pixels."""
words = title.split()
if not words:
return []
lines: List[str] = []
current = ""
for word in words:
candidate = f"{current} {word}".strip()
if _text_width(candidate) <= max_width or not current:
current = candidate
else:
lines.append(current)
current = word
if current:
lines.append(current)
return lines
def _set_pixel(pixels: List[List[Tuple[int, int, int]]], x: int, y: int,
color: Tuple[int, int, int], darken: Optional[float] = None) -> None:
"""Set one pixel: solid ``color``, or darken the existing pixel by ``darken``."""
if not 0 <= y < len(pixels):
return
if not 0 <= x < len(pixels[y]):
return
if darken is None:
pixels[y][x] = color
else:
r, g, b = pixels[y][x]
pixels[y][x] = (int(r * darken), int(g * darken), int(b * darken))
def _render_line(pixels: List[List[Tuple[int, int, int]]], text: str, x0: int, y0: int,
color: Tuple[int, int, int] = (0, 0, 0),
darken: Optional[float] = None) -> None:
"""Blit one line of bitmap text onto the pixel grid in place.
With ``darken``, each glyph pixel darkens whatever is underneath it
instead of painting a solid color (used for the drop shadow, which
stays tinted by the gradient behind it).
"""
for char_index, char in enumerate(text):
glyph = _FONT.get(char, _UNKNOWN_GLYPH)
x_off = x0 + char_index * (_GLYPH_WIDTH + 1) * _TEXT_SCALE
for gy, bits in enumerate(glyph):
for gx in range(_GLYPH_WIDTH):
if not bits & (1 << (_GLYPH_WIDTH - 1 - gx)):
continue
for dy in range(_TEXT_SCALE):
for dx in range(_TEXT_SCALE):
_set_pixel(pixels,
x_off + gx * _TEXT_SCALE + dx,
y0 + gy * _TEXT_SCALE + dy,
color, darken)
def _encode_png(width: int, height: int, pixels: List[List[Tuple[int, int, int]]]) -> bytes:
"""Encode an RGB pixel grid as a PNG using only the stdlib."""
def chunk(chunk_type: bytes, data: bytes) -> bytes:
payload = chunk_type + data
return (struct.pack(">I", len(data)) + payload
+ struct.pack(">I", zlib.crc32(payload) & 0xFFFFFFFF))
raw = b"".join(
b"\x00" + bytes(channel for pixel in scanline for channel in pixel)
for scanline in pixels
)
ihdr = struct.pack(">IIBBBBB", width, height, 8, 2, 0, 0, 0) # 8-bit RGB
return (b"\x89PNG\r\n\x1a\n"
+ chunk(b"IHDR", ihdr)
+ chunk(b"IDAT", zlib.compress(raw, 9))
+ chunk(b"IEND", b""))
def generate_cover(title: str, path: Path, width: int = COVER_WIDTH,
height: int = COVER_HEIGHT, seed: Optional[int] = None) -> Optional[Path]:
"""Write a gradient cover PNG with ``title`` centered on it.
``seed`` makes the gradient reproducible (used by tests). Returns the
path on success, or None when the PNG cannot be written (the audiobook
still gets tags, just without cover art).
"""
rng = random.Random(seed)
top_color = _random_light_color(rng)
bottom_color = _random_light_color(rng)
pixels = []
for y in range(height):
t = y / max(1, height - 1)
color = (_lerp(top_color[0], bottom_color[0], t),
_lerp(top_color[1], bottom_color[1], t),
_lerp(top_color[2], bottom_color[2], t))
pixels.append([color] * width)
lines = _wrap_title((title or "").strip(), width - 2 * _TEXT_MARGIN)
if lines:
line_height = _GLYPH_HEIGHT * _TEXT_SCALE + _TEXT_SCALE * 3
total_height = len(lines) * line_height
y_start = max(0, (height - total_height) // 2)
for line_index, line in enumerate(lines):
x0 = (width - _text_width(line)) // 2
y0 = y_start + line_index * line_height
# Paint order: drop shadow (the outlined glyph's full silhouette
# — glyph dilated by the stroke width — shifted down-right and
# darkened, tinted by the gradient underneath), then the black
# outline traced around the glyph, then the solid white text.
for dx in range(-_STROKE_WIDTH, _STROKE_WIDTH + 1):
for dy in range(-_STROKE_WIDTH, _STROKE_WIDTH + 1):
_render_line(pixels, line, x0 + dx + _SHADOW_OFFSET,
y0 + dy + _SHADOW_OFFSET, darken=_SHADOW_DARKEN)
for dx in range(-_STROKE_WIDTH, _STROKE_WIDTH + 1):
for dy in range(-_STROKE_WIDTH, _STROKE_WIDTH + 1):
_render_line(pixels, line, x0 + dx, y0 + dy,
color=_STROKE_COLOR)
_render_line(pixels, line, x0, y0, color=_TEXT_COLOR)
try:
path.write_bytes(_encode_png(width, height, pixels))
except OSError as exc:
logger.warning("Could not write cover image %s: %s", path, exc)
return None
logger.info("Generated cover: %s (gradient %s -> %s)", path, top_color, bottom_color)
return path
|
