I do not understand why in the following example, if I set patch_alpha=1.0, I do not see the shadow effect. I would expect to see it for the the rightmost four bars, where the original bars do not entirely occlude the shadow, so even if alpha is 1.0, there are parts of the shadow that are not behind the original bars and should still be visible.
import matplotlib.pyplot as plt
import matplotlib.patheffects as PathEffects
import numpy as np
np.random.seed(2358)
fig = plt.figure()
sime bar shadows
x = np.random.randn(1000)
n, bins, patches = plt.hist(x, bins=7)
shadow = PathEffects.withSimplePatchShadow(offset_xy=(10,-10), patch_alpha=0.8, shadow_rgbFace=(0.25,0.25,0.25))
for p in patches:
p.set_path_effects([shadow])
plt.show()
I now see that this line explains the behavior
https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/patheffects.py#L183
gc0.set_alpha(1.-self._patch_alpha)
so maybe I should amend my question: is this desirable that the shadow alpha is 1-patch_alpha, since an alpha of 1 on the patch does not imply that there is no visible shadow?
···
On Sat, Jul 14, 2012 at 11:48 AM, John Hunter <jdh2358@…287…> wrote:
I do not understand why in the following example, if I set patch_alpha=1.0, I do not see the shadow effect. I would expect to see it for the the rightmost four bars, where the original bars do not entirely occlude the shadow, so even if alpha is 1.0, there are parts of the shadow that are not behind the original bars and should still be visible.
I would argue that the shadow’s alpha should equal the patch’s alpha. The more opaque the patch, the less light that should get through. Could there have been an alpha blending reason for this?
Ben Root
···
On Saturday, July 14, 2012, John Hunter wrote:
On Sat, Jul 14, 2012 at 11:48 AM, John Hunter <jdh2358@…1003…7…> wrote:
I do not understand why in the following example, if I set patch_alpha=1.0, I do not see the shadow effect. I would expect to see it for the the rightmost four bars, where the original bars do not entirely occlude the shadow, so even if alpha is 1.0, there are parts of the shadow that are not behind the original bars and should still be visible.
I now see that this line explains the behavior
https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/patheffects.py#L183
gc0.set_alpha(1.-self._patch_alpha)
so maybe I should amend my question: is this desirable that the shadow alpha is 1-patch_alpha, since an alpha of 1 on the patch does not imply that there is no visible shadow?
>
>
>
>> I do not understand why in the following example, if I set
>> patch_alpha=1.0, I do not see the shadow effect. I would expect to see it
>> for the the rightmost four bars, where the original bars do not entirely
>> occlude the shadow, so even if alpha is 1.0, there are parts of the shadow
>> that are not behind the original bars and should still be visible.
>>
>>
>>
>
> I now see that this line explains the behavior
>
>
> https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/patheffects.py#L183
>
> gc0.set_alpha(1.-self._patch_alpha)
>
> so maybe I should amend my question: is this desirable that the shadow
> alpha is 1-patch_alpha, since an alpha of 1 on the patch does not imply
> that there is no visible shadow?
>
>
I would argue that the shadow's alpha should equal the patch's alpha. The
more opaque the patch, the less light that should get through. Could there
I am inclined to agree here. Should it instead be:
gc0.set_alpha(self._patch_alpha)?
···
On Sat, Jul 14, 2012 at 04:09:48PM -0400, Benjamin Root wrote:
On Saturday, July 14, 2012, John Hunter wrote:
> On Sat, Jul 14, 2012 at 11:48 AM, John Hunter <jdh2358@...287...<javascript:_e({}, 'cvml', 'jdh2358@...287...');> > > > wrote:
have been an alpha blending reason for this?
Ben Root
--
Damon McDougall
http://damon-is-a-geek.com
B2.39
Mathematics Institute
University of Warwick
Coventry
West Midlands
CV4 7AL
United Kingdom
I think it is me who put that code there. But I cannot recall why I did it.
I may have copied that behavior from other code, but cannot find which.
Yes, I agree that the current behavior is not very desirable.
So, anyone who have an idea how this should behave, please go ahead
and fix this.
Regards,
-JJ
···
On Sun, Jul 15, 2012 at 1:54 AM, John Hunter <jdh2358@...287...> wrote:
On Sat, Jul 14, 2012 at 11:48 AM, John Hunter <jdh2358@...287...> wrote:
I do not understand why in the following example, if I set
patch_alpha=1.0, I do not see the shadow effect. I would expect to see it
for the the rightmost four bars, where the original bars do not entirely
occlude the shadow, so even if alpha is 1.0, there are parts of the shadow
that are not behind the original bars and should still be visible.
I now see that this line explains the behavior
https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/patheffects.py#L183
gc0.set_alpha(1.-self._patch_alpha)
so maybe I should amend my question: is this desirable that the shadow alpha
is 1-patch_alpha, since an alpha of 1 on the patch does not imply that there
is no visible shadow?