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fix: discrete log color sampling: build continuous log CTF before samp… #75

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Merged
jourdain merged 1 commit into from
May 1, 2026
Merged

fix: discrete log color sampling: build continuous log CTF before samp… #75

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25 changes: 19 additions & 6 deletions src/e3sm_quickview/view_manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -427,7 +427,8 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
pct = (np.log10(bv) - log_min) / log_range_val * 100 if log_range_val else 0
self._discrete_tick_data.append({"val": bv, "pos": float(pct)})

# Build a temporary linear CTF from the saved linear RGB points
# Build a continuous log CTF so discrete bands sample colours that
# match the continuous log rendering.
from vtkmodules.vtkRenderingCore import vtkColorTransferFunction

linear_ctf = vtkColorTransferFunction()
Expand All @@ -439,9 +440,21 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
linear_rgb_points[i + 3],
)

n_samples = 256
log_vals = np.linspace(log_min, log_max, n_samples)
log_ctf = vtkColorTransferFunction()
rgb_tmp = [0.0, 0.0, 0.0]
for lg in log_vals:
v = 10.0**lg
v = max(x_min, min(x_max, v))
t = (lg - log_min) / log_range
x_lookup = x_min + t * data_range
linear_ctf.GetColor(x_lookup, rgb_tmp)
log_ctf.AddRGBPoint(v, rgb_tmp[0], rgb_tmp[1], rgb_tmp[2])

rgb = [0.0, 0.0, 0.0]
eps_data = data_range * 1e-9
eps_lin = 1e-9
eps_lin = data_range * 1e-9
display_rgb_points = []
render_rgb_points = []
band_idx = 0
Expand All @@ -456,10 +469,10 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
log_lo_decade + (log_hi_decade - log_lo_decade) * (j + 1) / n_sub
)
log_mid = (log_lo + log_hi) / 2.0
# Sample color from linear LUT at normalized position
t_mid = (log_mid - log_min) / log_range
x_lookup = x_min + t_mid * data_range
linear_ctf.GetColor(x_lookup, rgb)
# Sample color from continuous log CTF at sub-band midpoint
v_mid = 10.0**log_mid
v_mid = max(x_min, min(x_max, v_mid))
log_ctf.GetColor(v_mid, rgb)
r, g, b = float(rgb[0]), float(rgb[1]), float(rgb[2])

# Data-space boundaries for rendering
Expand Down
25 changes: 19 additions & 6 deletions src/e3sm_quickview/view_manager2.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -427,7 +427,8 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
pct = (np.log10(bv) - log_min) / log_range_val * 100 if log_range_val else 0
self._discrete_tick_data.append({"val": bv, "pos": float(pct)})

# Build a temporary linear CTF from the saved linear RGB points
# Build a continuous log CTF so discrete bands sample colours that
# match the continuous log rendering.
from vtkmodules.vtkRenderingCore import vtkColorTransferFunction

linear_ctf = vtkColorTransferFunction()
Expand All @@ -439,9 +440,21 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
linear_rgb_points[i + 3],
)

n_samples = 256
log_vals = np.linspace(log_min, log_max, n_samples)
log_ctf = vtkColorTransferFunction()
rgb_tmp = [0.0, 0.0, 0.0]
for lg in log_vals:
v = 10.0**lg
v = max(x_min, min(x_max, v))
t = (lg - log_min) / log_range
x_lookup = x_min + t * data_range
linear_ctf.GetColor(x_lookup, rgb_tmp)
log_ctf.AddRGBPoint(v, rgb_tmp[0], rgb_tmp[1], rgb_tmp[2])

rgb = [0.0, 0.0, 0.0]
eps_data = data_range * 1e-9
eps_lin = 1e-9
eps_lin = data_range * 1e-9
display_rgb_points = []
render_rgb_points = []
band_idx = 0
Expand All @@ -456,10 +469,10 @@ def _apply_discrete_log_to_lut(self, linthresh, linear_rgb_points, n_sub=1):
log_lo_decade + (log_hi_decade - log_lo_decade) * (j + 1) / n_sub
)
log_mid = (log_lo + log_hi) / 2.0
# Sample color from linear LUT at normalized position
t_mid = (log_mid - log_min) / log_range
x_lookup = x_min + t_mid * data_range
linear_ctf.GetColor(x_lookup, rgb)
# Sample color from continuous log CTF at sub-band midpoint
v_mid = 10.0**log_mid
v_mid = max(x_min, min(x_max, v_mid))
log_ctf.GetColor(v_mid, rgb)
r, g, b = float(rgb[0]), float(rgb[1]), float(rgb[2])

# Data-space boundaries for rendering
Expand Down
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