pyplot.plot conflict: markerfacecolor ='none' and alpha

Bug report

Bug summary
I tried to use a previously-works-fine code to make a plot but failed to reproduce the same one -- after updating matplotlib to 2.2. The hollow circles in plot (defined by markerfacecolor='None') are now in black facecolor. After manually locating the error, I found that the keyword 'alpha' seems conflict to markerfacecolor = 'None' which never happened before. This conflict will only affect facecolor set as 'None'.

Code for reproduction

import matplotlib.pyplot as plt
# This works properly
plt.figure()
plt.plot([1,2,3],[1,2,3],'o',c='g',markeredgecolor='g',markersize = 10,markerfacecolor='r',linewidth=2,alpha=1)
plt.show()
# markerfacecolor='none' conflicts with alpha keyword
plt.figure()
plt.plot([1,2,3],[1,2,3],'o',c='g',markeredgecolor='g',markersize = 10,markerfacecolor='none',linewidth=2,alpha=1)
plt.show()
# markerfacecolor='none' conflicts with alpha keyword, and this happens on different alphas
plt.figure()
plt.plot([1,2,3],[1,2,3],'o',c='g',markeredgecolor='g',markersize = 10,markerfacecolor='none',linewidth=2,alpha=0.5)
plt.show()
# remove alpha keyword and markerfacecolor='none' works well
plt.figure()
plt.plot([1,2,3],[1,2,3],'o',c='g',markeredgecolor='g',markersize = 10,markerfacecolor='none',linewidth=2) # no alpha here
plt.show()

Actual outcome

![1](https://user-images.githubusercontent.com/13745875/39099965-ee512c2c-4650-11e8-9cc4-969ebe75ac2a.png)
![2](https://user-images.githubusercontent.com/13745875/39099966-ee604bb2-4650-11e8-9245-d846bbed9523.png)
![3](https://user-images.githubusercontent.com/13745875/39099968-ee6aa2f6-4650-11e8-8420-bde423460955.png)
![4](https://user-images.githubusercontent.com/13745875/39099969-ee73fbbc-4650-11e8-9358-72e00202e539.png)

Matplotlib version

Operating system: Windows 10 x64
Matplotlib version: 2.2
Matplotlib backend (print(matplotlib.get_backend())): both terminal ipython (Qt5Agg) and jupyter notebook (module://ipykernel.pylab.backend_inline)
Python version: 3.6.2
Jupyter version (if applicable): 4.3.0
Other libraries: N/A

matplotlib and python installed by conda

channel by default

Thanks a lot!

This is reproducible on current master. print(line.get_markerfacecolor()) prints "none" correctly, so this might happen at draw time?!

Bisects to #9911. Humpf...

After some investigation, turns out that the signature

    def draw_markers(self, gc, marker_path, marker_trans, path,
                     trans, rgbFace=None):

indeed requires rgbFace to possibly be None. The face color is converted per

    if (!convert_face(faceobj, gc, &face)) {
        return NULL;
    }

and convert_face explicitly checks for None at

int convert_face(PyObject *color, GCAgg &gc, agg::rgba *rgba)
{
    if (!convert_rgba(color, rgba)) {
        return 0;
    }

    if (color != NULL && color != Py_None) {  // <-- HERE.
        if (gc.forced_alpha || PySequence_Size(color) == 3) {
            rgba->a = gc.alpha;
        }
    }

    return 1;
}

Looks like the "easy" fix is to manually revert the relevant parts of #9911.

Actually I have a better fix coming.

Navigation Menu

Repository navigation

pyplot.plot conflict: markerfacecolor ='none' and alpha #11104

Bug report

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

pyplot.plot conflict: markerfacecolor ='none' and alpha #11104

Description

Bug report

Activity

ImportanceOfBeingErnest commented on Apr 22, 2018

anntzer commented on Apr 22, 2018

anntzer commented on Apr 22, 2018

anntzer commented on Apr 23, 2018

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions