This merged VAE improves anime-style shading by refining the color balance and reducing visible gaps between lineart and fill colors.
The merge also suppresses the white fringe that can appear between dark outlines and flat color areas, resulting in cleaner edges and more stable rendering.
Highlights keep a slight cool tint while shadows remain warm, producing smoother gradients and cleaner soft warm tones commonly used in stylized anime rendering.
As a trade-off, pink tones may appear slightly stronger in some situations, especially with warm lighting or high saturation.
This behavior helps avoid muddy gradients, but it may not fit all styles.
This VAE was tested with Qwen-based image models, but it is also compatible with Anima-based models that use the same VAE format, and can be used as a drop-in replacement in most Anima workflows.
from PIL import ImageEnhance
PALE_ORANGE = (238, 196, 172)
LIGHT_BROWN = (198, 122, 96)
DARK_BROWN = (110, 58, 42)
PURE_BLACK = (18, 18, 18)
def clamp8(x):
return max(0, min(255, int(round(x))))
def lerp(a, b, t):
return a + (b - a) * t
def smoothstep(edge0, edge1, x):
if edge0 == edge1:
return 1.0 if x >= edge1 else 0.0
t = (x - edge0) / (edge1 - edge0)
t = max(0.0, min(1.0, t))
return t * t * (3.0 - 2.0 * t)
def apply_gamma_u8(v, gamma):
x = max(0.0, min(1.0, v / 255.0))
return clamp8(255.0 * (x ** gamma))
def dist3(r1, g1, b1, r2, g2, b2):
dr = r1 - r2
dg = g1 - g2
db = b1 - b2
return dr * dr + dg * dg + db * db
def snap_to_palette(rr, gg, bb, palette, strength=1.0):
best = None
best_d = None
for pr, pg, pb in palette:
d = dist3(rr, gg, bb, pr, pg, pb)
if best_d is None or d < best_d:
best_d = d
best = (pr, pg, pb)
pr, pg, pb = best
rr = lerp(rr, pr, strength)
gg = lerp(gg, pg, strength)
bb = lerp(bb, pb, strength)
return rr, gg, bb
def preprocess_anime_color(img):
img = ImageEnhance.Brightness(img).enhance(1.10)
img = ImageEnhance.Color(img).enhance(1.04)
img = ImageEnhance.Contrast(img).enhance(1.04)
r, g, b = img.split()
r = r.point(lambda x: clamp8(x * 1.07))
g = g.point(lambda x: clamp8(x * 1.04))
b = b.point(lambda x: clamp8(x * 0.98))
img = img.merge("RGB", (r, g, b))
px = img.load()
w, h = img.size
for y in range(h):
for x in range(w):
rr, gg, bb = px[x, y]
lum = (rr + gg + bb) / 3
maxc = max(rr, gg, bb)
minc = min(rr, gg, bb)
sat = maxc - minc
avg = (rr + gg + bb) / 3
warm = rr > gg > bb
# shadow S curve
shadow_w = 1.0 - smoothstep(70, 115, lum)
if shadow_w > 0:
factor = (max(lum, 1) / 100.0) ** 1.2
rr = lerp(rr, rr * factor, shadow_w)
gg = lerp(gg, gg * factor, shadow_w)
bb = lerp(bb, bb * factor, shadow_w)
# mid tone fix
midgray_w = smoothstep(75, 95, lum) * (1.0 - smoothstep(120, 140, lum))
low_sat_w = 1.0 - smoothstep(65, 90, sat)
fix_w = midgray_w * low_sat_w
if fix_w > 0:
rr = lerp(rr, avg + (rr - avg) * 0.85, fix_w)
gg = lerp(gg, avg + (gg - avg) * 0.85, fix_w)
bb = lerp(bb, avg + (bb - avg) * 0.75, fix_w)
# lift shadow
shadow_lift_w = smoothstep(90, 105, lum) * (1.0 - smoothstep(135, 150, lum))
if shadow_lift_w > 0:
rr = lerp(rr, rr * 1.04 + 4, shadow_lift_w)
gg = lerp(gg, gg * 1.04 + 4, shadow_lift_w)
bb = lerp(bb, bb * 1.04 + 4, shadow_lift_w)
# gamma skin
midtone_w = smoothstep(70, 95, lum) * (1.0 - smoothstep(170, 195, lum))
if midtone_w > 0:
rr_gamma = apply_gamma_u8(rr, 0.95)
rr = lerp(rr, rr_gamma, midtone_w)
# highlight transparency
if warm:
bright_w = smoothstep(125, 145, lum)
highlight_w = smoothstep(205, 225, lum)
if bright_w > 0:
rr = lerp(rr, rr * 1.04, bright_w)
gg = lerp(gg, gg * 1.03, bright_w)
bb = lerp(bb, bb * 0.94, bright_w)
if highlight_w > 0:
rr = lerp(rr, rr * 1.02, highlight_w)
bb = lerp(bb, bb * 1.05, highlight_w)
# pink fringe fix
fringe_w = 1.0 - smoothstep(10, 22, sat)
if fringe_w > 0:
gray = avg
rr = lerp(rr, gray, fringe_w * 0.9)
gg = lerp(gg, gray, fringe_w * 0.9)
bb = lerp(bb, gray, fringe_w * 0.9)
# boundary cleanup
boundary_w = smoothstep(55, 105, lum) * (1.0 - smoothstep(150, 185, lum))
pinkish_w = smoothstep(8, 22, rr - gg) * (1.0 - smoothstep(28, 55, gg - bb))
fix_boundary = boundary_w * pinkish_w
if fix_boundary > 0:
rr = lerp(rr, rr * 0.96, fix_boundary)
gg = lerp(gg, gg * 1.01, fix_boundary)
bb = lerp(bb, bb * 0.90, fix_boundary)
# palette snap
warm_skin_like = rr > gg > bb
if warm_skin_like:
if lum > 170:
pal = [PALE_ORANGE, LIGHT_BROWN]
s = 0.7
elif lum > 95:
pal = [LIGHT_BROWN, DARK_BROWN]
s = 0.8
else:
pal = [DARK_BROWN, PURE_BLACK]
s = 0.85
rr, gg, bb = snap_to_palette(rr, gg, bb, pal, s)
px[x, y] = (
clamp8(rr),
clamp8(gg),
clamp8(bb),
)
return img