[GitHub] bignamehyp opened a new pull request #7756: The order of hue composed transformation

[gi...@git.apache.org]

bignamehyp opened a new pull request #7756: The order of hue composed transformation
URL: https://github.com/apache/incubator-mxnet/pull/7756
 
 
   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
 
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