nodes/bemoregt-ComfyUI_PhaseStretchTransform
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fix: correct PST kernel formula per paper Eq.5

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Previous kernel incorrectly modified both amplitude and phase:
  (W*R/(1+W*R)) * exp(-j*S*R/(1+R))

Corrected to unit-amplitude pure-phase kernel as defined in the paper:
  K = exp(j * S * W*R/(1+W*R))

Also updated default thresholds to symmetric ±0.35 which is appropriate
for the corrected phase range of approximately [-S, S] = [-0.48, 0.48].

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
bemoregt
2026-03-22 18:03:05 +09:00
co-authored by Claude Sonnet 4.6
parent 9dd30cc32f
commit ce73aaa91c
1 changed files with 11 additions and 8 deletions
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pst_node.py
+11 -8
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@@ -8,8 +8,8 @@ def phase_stretch_transform(img_gray: np.ndarray,
phase_strength: float = 0.48,
warp_strength: float = 12.14,
morph_flag: bool = True,
min_thresh: float = -1.0,
max_thresh: float = 0.003) -> tuple[np.ndarray, np.ndarray]:
min_thresh: float = -0.35,
max_thresh: float = 0.35) -> tuple[np.ndarray, np.ndarray]:
"""
Phase Stretch Transform (PST)
@@ -31,10 +31,13 @@ def phase_stretch_transform(img_gray: np.ndarray,
img_fft = np.fft.fftshift(np.fft.fft2(img_gray.astype(np.float64)))
img_filtered = img_fft * lpf
# ── PST kernel (warped phase ramp) ───────────────────────────────────────
# ── PST kernel (warped phase ramp, Eq.5 in paper) ────────────────────────
# K[u,v] = exp(j * S * phi_w) where phi_w = W*R / (1 + W*R)
# Unit-amplitude, pure-phase kernel — amplitude must NOT be modified.
W_val = warp_strength
S_val = phase_strength
pst_kernel = (W_val * R / (1.0 + W_val * R)) * np.exp(-1j * S_val * R / (1.0 + R))
phi_w = W_val * R / (1.0 + W_val * R) # warped phase ramp ∈ [0, 1)
pst_kernel = np.exp(1j * S_val * phi_w) # pure phase kernel
img_pst = np.fft.ifft2(np.fft.ifftshift(img_filtered * pst_kernel))
@@ -79,12 +82,12 @@ class PhaseStretchTransformNode:
"tooltip": "PST warp strength (W)"
}),
"min_thresh": ("FLOAT", {
"default": -1.0, "min": -3.15, "max": 0.0, "step": 0.001,
"tooltip": "Lower phase threshold for binary edge map"
"default": -0.35, "min": -3.15, "max": 0.0, "step": 0.001,
"tooltip": "Lower phase threshold for binary edge map (range ≈ -phase_strength to 0)"
}),
"max_thresh": ("FLOAT", {
"default": 0.003, "min": 0.0, "max": 3.15, "step": 0.001,
"tooltip": "Upper phase threshold for binary edge map"
"default": 0.35, "min": 0.0, "max": 3.15, "step": 0.001,
"tooltip": "Upper phase threshold for binary edge map (range ≈ 0 to phase_strength)"
}),
"morph_flag": ("BOOLEAN", {
"default": True,