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new ec363d1 The order of hue composed transformation (#7756)
ec363d1 is described below
commit ec363d11689d63d02c55c6aecfa9a17b457fd5ce
Author: Yanping Huang <[email protected]>
AuthorDate: Thu Sep 7 17:15:37 2017 -0700
The order of hue composed transformation (#7756)
* The order of hue composed transformation
was incorrect.
According to https://beesbuzz.biz/code/hsv_color_transforms.php
The final composed transform should be T_hsv = T_rgb * T_H * T_S * T_V *
T_YIQ
translating to
t = np.dot(np.dot(self.ityiq, bt), self.tyiq).T
With this correction, you can also change hue and saturation at the same
time as in https://beesbuzz.biz/code/hsv_color_transforms.php.
For example:
su = alpha_s * np.cos(alpha_h * np.pi)
sw = alpha_s * np.sin(alpha_h * np.pi)
bt = np.array([[alpha_v, 0.0, 0.0],
[0.0, su, -sw],
[0.0, sw, su]])
t = np.dot(np.dot(self.ityiq, bt), self.tyiq).T
src = nd.dot(src, nd.array(t))
return src
* vsw/vsu means v*s*w/v*s*u
here only hue is changed, while v and s remain the same.
---
python/mxnet/image/image.py | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/python/mxnet/image/image.py b/python/mxnet/image/image.py
index d99db21..18563cd 100644
--- a/python/mxnet/image/image.py
+++ b/python/mxnet/image/image.py
@@ -727,12 +727,12 @@ class HueJitterAug(Augmenter):
https://beesbuzz.biz/code/hsv_color_transforms.php
"""
alpha = random.uniform(-self.hue, self.hue)
- vsu = np.cos(alpha * np.pi)
- vsw = np.sin(alpha * np.pi)
+ u = np.cos(alpha * np.pi)
+ w = np.sin(alpha * np.pi)
bt = np.array([[1.0, 0.0, 0.0],
- [0.0, vsu, -vsw],
- [0.0, vsw, vsu]])
- t = np.dot(np.dot(self.tyiq, bt), self.ityiq).T
+ [0.0, u, -w],
+ [0.0, w, u]])
+ t = np.dot(np.dot(self.ityiq, bt), self.tyiq).T
src = nd.dot(src, nd.array(t))
return src
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