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import os
import random
from wand.image import Image
from wand.drawing import Drawing
from wand.color import Color
def load_dataset(captcha_dir: str) -> list:
dataset = []
for entry in os.scandir(captcha_dir):
if not entry.is_dir():
continue
count = sum(
1 for f in os.scandir(entry.path)
if f.is_file() and f.name.endswith(".png")
)
if count > 0:
dataset.append([entry.name, count])
if len(dataset) < 2:
raise ValueError(
f"captcha_dir '{captcha_dir}' must contain at least 2 category "
f"sub-folders with .png images; found {len(dataset)}."
)
return dataset
def generate_captcha_image(
captcha_dir: str,
font_path: str = "./data/fonts/captcha.ttf",
minimum_ans: int = 3,
maximum_ans: int = 5
) -> tuple[list[int], bytes]:
captcha_dataset = load_dataset(captcha_dir)
pool = list(range(1, 16)) #[1, 2, ..., 15]
picks = random.randint(minimum_ans, maximum_ans)
answer_pos = []
for i in range(picks): # pick random answer slots first
idx = random.randint(0, len(pool)-1)
answer_pos.append(pool.pop(idx))
c = len(captcha_dataset)
chosen = captcha_dataset[random.randint(0, c-1)] # choose a dataset
choices = [ds for ds in captcha_dataset if ds[0] != chosen[0]] # wrong answers
grid = []
for i in range(16):
if i in answer_pos:
grid.append(chosen)
else:
grid.append(choices[random.randint(0, len(choices) - 1)])
# top banner bg
if random.randint(0, 1) == 0:
theme = {"bg": "#ebdbb2", "fg": "#1d2021"}
else:
theme = {"bg": "#1d2021", "fg": "#ebdbb2"}
noise_types = ["gaussian", "laplacian"]
distort_types = ["affine", "shepards"]
with Image(width=400, height=427, background=Color(theme["bg"])) as im:
im.format = "jpeg"
im.background_color = Color(theme["bg"])
for idx in range(16):
row = idx // 4
col = idx % 4
img_path = os.path.join(
captcha_dir,
grid[idx][0],
f"{random.randint(1, grid[idx][1])}.png",
)
with Image(filename=img_path) as tile:
tile.background_color = Color("black")
tile.alpha_channel = "remove"
if random.randint(0, 1) == 1:
tile.flop()
tile.distort(
distort_types[random.randint(0, 1)],
[
0, 0, random.randint(-15, 15), random.randint(-15, 15),
100, 0, random.randint(80, 120), random.randint(-15, 15),
100, 100, random.randint(80, 120), random.randint(80, 120),
0, 100, random.randint(-15, 15), random.randint(80, 120),
],
best_fit=False,
)
tile.noise(noise_types[random.randint(0, 1)])
im.composite(tile, left=col * 100, top=(row * 100) + 27)
label = f"Pick {picks} images of {chosen[0].replace('_', ' ')}"
with Drawing() as draw:
draw.font = font_path
draw.font_size = 24
draw.fill_color = Color(theme["fg"])
full_metrics = draw.get_font_metrics(im, label)
pos_x = 200 - (full_metrics.text_width / 2)
for char in label:
char_metrics = draw.get_font_metrics(im, char)
draw.push()
draw.translate(pos_x, 22)
draw.rotate(random.randint(-15, 15))
draw.text(0, 0, char)
draw.pop()
pos_x += char_metrics.text_width
draw(im)
im.compression_quality = 90
return answer_pos, im.make_blob("jpeg")
if __name__ == "__main__":
import sys
positions, blob = generate_captcha_image(
captcha_dir="../captcha",
font_path="../data/fonts/captcha.ttf",
)
out = "captcha_out.jpg"
with open(out, "wb") as fh:
fh.write(blob)
print(f"Answer positions : {positions}", file=sys.stderr)
print(f"Image saved to : {out}", file=sys.stderr)
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