<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong><br>
The marker edges are not painted nicely on the edge of the marker.</p>
<p dir="auto"><strong>Code for reproduction</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib.pyplot as plt
x = [42,43,44]
y=[42,43,44]
plt.scatter(x,y,alpha=0.7,sizes=[500], linewidths=[15], marker='s')
plt.savefig('sample.pdf')"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>
<span class="pl-s1">x</span> <span class="pl-c1">=</span> [<span class="pl-c1">42</span>,<span class="pl-c1">43</span>,<span class="pl-c1">44</span>]
<span class="pl-s1">y</span><span class="pl-c1">=</span>[<span class="pl-c1">42</span>,<span class="pl-c1">43</span>,<span class="pl-c1">44</span>]
<span class="pl-s1">plt</span>.<span class="pl-en">scatter</span>(<span class="pl-s1">x</span>,<span class="pl-s1">y</span>,<span class="pl-s1">alpha</span><span class="pl-c1">=</span><span class="pl-c1">0.7</span>,<span class="pl-s1">sizes</span><span class="pl-c1">=</span>[<span class="pl-c1">500</span>], <span class="pl-s1">linewidths</span><span class="pl-c1">=</span>[<span class="pl-c1">15</span>], <span class="pl-s1">marker</span><span class="pl-c1">=</span><span class="pl-s">'s'</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">savefig</span>(<span class="pl-s">'sample.pdf'</span>)</pre></div>
<p dir="auto"><strong>Actual outcome</strong></p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/11406002/62953572-0f6a4680-bdee-11e9-98db-6098d1eacc13.png"><img src="https://user-images.githubusercontent.com/11406002/62953572-0f6a4680-bdee-11e9-98db-6098d1eacc13.png" alt="image" style="max-width: 100%;"></a><br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/11406002/62953605-21e48000-bdee-11e9-8548-c935e27564be.png"><img src="https://user-images.githubusercontent.com/11406002/62953605-21e48000-bdee-11e9-8548-c935e27564be.png" alt="image" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Expected outcome</strong><br>
The edges should go cleanly around the marker boundary.</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/11406002/62954167-3117fd80-bdef-11e9-8f1f-7180094fd4ff.png"><img src="https://user-images.githubusercontent.com/11406002/62954167-3117fd80-bdef-11e9-8f1f-7180094fd4ff.png" alt="image" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Matplotlib version</strong></p>
<ul dir="auto">
<li>MacOS 10.14.5</li>
<li>Matplotlib v3.1.1</li>
<li>Matplotlib backend: MacOSX</li>
<li>Python 3.6.7</li>
</ul>
<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>
<p dir="auto">Marker edge overlaps with marker and the edge appears to be double the width specified. This becomes obvious when you use alpha transparency and a very larger point marker with a large edge width or in the case where I noticed it a small figure (about 2 inches wide) with the default rcParams.</p>
<h3 dir="auto"></h3>
<p dir="auto">Code for reproduction</p>

<p dir="auto"><strong>Case 1: very large point with a large edge width</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="plt.figure()
plt.plot(1, '.', ms=200, mew=50, alpha=0.5)"><pre class="notranslate"><span class="pl-s1">plt</span>.<span class="pl-en">figure</span>()
<span class="pl-s1">plt</span>.<span class="pl-en">plot</span>(<span class="pl-c1">1</span>, <span class="pl-s">'.'</span>, <span class="pl-s1">ms</span><span class="pl-c1">=</span><span class="pl-c1">200</span>, <span class="pl-s1">mew</span><span class="pl-c1">=</span><span class="pl-c1">50</span>, <span class="pl-s1">alpha</span><span class="pl-c1">=</span><span class="pl-c1">0.5</span>)</pre></div>
<p dir="auto"><strong>Case 2: very small figure with default rcParams: markersize = 8, markeredgewidth=1.0</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="plt.figure(figsize=(1,1), dpi=600)
plt.plot(1, '.', alpha=0.5)"><pre class="notranslate"><span class="pl-s1">plt</span>.<span class="pl-en">figure</span>(<span class="pl-s1">figsize</span><span class="pl-c1">=</span>(<span class="pl-c1">1</span>,<span class="pl-c1">1</span>), <span class="pl-s1">dpi</span><span class="pl-c1">=</span><span class="pl-c1">600</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">plot</span>(<span class="pl-c1">1</span>, <span class="pl-s">'.'</span>, <span class="pl-s1">alpha</span><span class="pl-c1">=</span><span class="pl-c1">0.5</span>)</pre></div>
<p dir="auto"><strong>Actual outcome</strong><br>
In this figure I have markersize=200 and markeredgewith=50. There is an ugly ring and it looks as if the marker edges are two times wider (100 instead of 50) than I asked.<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/4636304/52240809-f6f9fc00-289f-11e9-90cd-7dd3832268c6.png"><img src="https://user-images.githubusercontent.com/4636304/52240809-f6f9fc00-289f-11e9-90cd-7dd3832268c6.png" alt="figure_1" style="max-width: 100%;"></a><br>
Now in this figure I have markersize=200 and markeredgewidth=99. There is a single pixel in the center that is faded blue thus the markeredges are definitely twice what I asked for. If I set the markeredgewith to 100 I get a solid core.<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/4636304/52240852-1db83280-28a0-11e9-9515-13995a4faae2.png"><img src="https://user-images.githubusercontent.com/4636304/52240852-1db83280-28a0-11e9-9515-13995a4faae2.png" alt="figure_2" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Expected outcome</strong><br>
I would expect that the marker edge would line up perfectly with the marker core. In this plot I set markersize to 300 (200 plus 2*50 edges) to get the same size as the original without the ugly ring.<br>
<a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/4636304/52240884-3cb6c480-28a0-11e9-8114-966593fac680.png"><img src="https://user-images.githubusercontent.com/4636304/52240884-3cb6c480-28a0-11e9-8114-966593fac680.png" alt="figure_3" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Matplotlib version</strong></p>
<ul dir="auto">
<li>Operating system: macOS 10.13</li>
<li>Matplotlib version: 3.0.2</li>
<li>Matplotlib backend: both with Qt and PGF backends</li>
<li>Python version: 3.7.2</li>
<li>matplotlib installed via pip</li>
</ul>