from PIL import Image, ImageEnhance, ImageFilter

img = Image.open('/tmp/haiyi_captcha_raw.png').convert('L')

# Contrast x3
enhancer = ImageEnhance.Contrast(img)
img = enhancer.enhance(3.0)

# Sharpen
img = img.filter(ImageFilter.SHARPEN)

# Threshold 128 -> black & white
img = img.point(lambda p: 255 if p > 128 else 0)

# 5x NEAREST resize
w, h = img.size
img = img.resize((w * 5, h * 5), Image.NEAREST)

img.save('/tmp/haiyi_captcha_enhanced.png')
print(f"OK|size={img.size}")