Preserve aspect ratio if Pillow available

Since we are controlling the scaling, we can manage
things more precisely and get the aspect ratio right.

confluent_client/bin/nodeconsole

@@ -257,10 +257,21 @@ def draw_image(data, width, height, doscale=True):
             errstr = 'Error rendering image:\n' + str(e)
             return draw_text(errstr, width, height)
         imgwidth, imgheight = get_pix_dimensions(width, height)
-        img = img.resize((imgwidth - 4, imgheight - 4))
-        nimg = Image.new(mode='RGB', size=(img.width + 4, img.height + 4), color='black')
+        nimg = Image.new(mode='RGBA', size=(imgwidth, imgheight))
+        imgwidth -= 4
+        imgheight -= 4
+        hscalefact = imgwidth / img.width
+        vscalefact = imgheight / img.height
+        if hscalefact < vscalefact:
+            rzwidth = imgwidth
+            rzheight = int(img.height * hscalefact)
+        else:
+            rzwidth = int(img.width * vscalefact)
+            rzheight = imgheight
+        img = img.resize((rzwidth, rzheight))
         nd = ImageDraw.Draw(nimg)
-        nd.rectangle((0, 0, nimg.width - 1, nimg.height -1), outline='white', width=1)
+        nd.rectangle((1, 1, rzwidth + 2, rzheight + 2), outline='black', width=1)
+        nd.rectangle((0, 0, rzwidth + 3, rzheight + 3), outline='white', width=1)
         nimg.paste(img, box=(2, 2))
         outfile = io.BytesIO()
         nimg.save(outfile, format='PNG')