fixed issue 4179 by updating matplotlib text scaling

qiskit/visualization/matplotlib.py

@@ -44,7 +44,6 @@
 
 WID = 0.65
 HIG = 0.65
-DEFAULT_SCALE = 4.3
 PORDER_GATE = 5
 PORDER_LINE = 3
 PORDER_REGLINE = 2
@@ -111,7 +110,7 @@ def __init__(self, qregs, cregs, ops,
                               'To install, run "pip install matplotlib".')
 
         self._ast = None
-        self._scale = DEFAULT_SCALE * scale
+        self._scale = scale
         self._creg = []
         self._qreg = []
         self._registers(cregs, qregs)
@@ -220,26 +219,26 @@ def _custom_multiqubit_gate(self, xy, cxy=None, fc=None, wide=True, text=None,
         # Annotate inputs
         for bit, y in enumerate([x[1] for x in xy]):
             self.ax.text(xpos - 0.45 * wid, y, str(bit), ha='left', va='center',
-                         fontsize=self._style.fs, color=self._style.gt,
+                         fontsize=self._scale * self._style.fs, color=self._style.gt,
                          clip_on=True, zorder=PORDER_TEXT)
 
         if text:
 
             disp_text = text
             if subtext:
                 self.ax.text(xpos, ypos + 0.5 * height, disp_text, ha='center',
-                             va='center', fontsize=self._style.fs,
+                             va='center', fontsize=self._scale * self._style.fs,
                              color=self._style.gt, clip_on=True,
                              zorder=PORDER_TEXT)
                 self.ax.text(xpos, ypos + 0.3 * height, subtext, ha='center',
-                             va='center', fontsize=self._style.sfs,
+                             va='center', fontsize=self._scale * self._style.sfs,
                              color=self._style.sc, clip_on=True,
                              zorder=PORDER_TEXT)
             else:
                 self.ax.text(xpos, ypos + .5 * (qubit_span - 1), disp_text,
                              ha='center',
                              va='center',
-                             fontsize=self._style.fs,
+                             fontsize=self._scale * self._style.fs,
                              color=self._style.gt,
                              clip_on=True,
                              zorder=PORDER_TEXT,
@@ -297,16 +296,16 @@ def _gate(self, xy, fc=None, wide=False, text=None, subtext=None):
                 disp_text = text
             if subtext:
                 self.ax.text(xpos, ypos + 0.15 * HIG, disp_text, ha='center',
-                             va='center', fontsize=font_size,
+                             va='center', fontsize=self._scale * font_size,
                              color=disp_color, clip_on=True,
                              zorder=PORDER_TEXT)
                 self.ax.text(xpos, ypos - 0.3 * HIG, subtext, ha='center',
-                             va='center', fontsize=sub_font_size,
+                             va='center', fontsize=self._scale * sub_font_size,
                              color=sub_color, clip_on=True,
                              zorder=PORDER_TEXT)
             else:
                 self.ax.text(xpos, ypos, disp_text, ha='center', va='center',
-                             fontsize=font_size,
+                             fontsize=self._scale * font_size,
                              color=disp_color,
                              clip_on=True,
                              zorder=PORDER_TEXT)
@@ -315,7 +314,7 @@ def _subtext(self, xy, text):
         xpos, ypos = xy
 
         self.ax.text(xpos, ypos - 0.3 * HIG, text, ha='center', va='top',
-                     fontsize=self._style.sfs,
+                     fontsize=self._scale * self._style.sfs,
                      color=self._style.tc,
                      clip_on=True,
                      zorder=PORDER_TEXT)
@@ -327,7 +326,7 @@ def _sidetext(self, xy, text):
         # another 0.0375 over
         xp = xpos + 0.15 + (0.0375 * len(text))
         self.ax.text(xp, ypos + HIG, text, ha='center', va='top',
-                     fontsize=self._style.sfs,
+                     fontsize=self._scale * self._style.sfs,
                      color=self._style.tc,
                      clip_on=True,
                      zorder=PORDER_TEXT)
@@ -392,7 +391,7 @@ def _measure(self, qxy, cxy, cid):
         # target
         if self._style.bundle:
             self.ax.text(cx + .25, cy + .1, str(cid), ha='left', va='bottom',
-                         fontsize=0.8 * self._style.fs,
+                         fontsize=self._scale * 0.8 * self._style.fs,
                          color=self._style.tc,
                          clip_on=True,
                          zorder=PORDER_TEXT)
@@ -520,7 +519,7 @@ def draw(self, filename=None, verbose=False):
         fig_w = _xr - _xl
         fig_h = _yt - _yb
         if self._style.figwidth < 0.0:
-            self._style.figwidth = fig_w * self._scale * self._style.fs / 72 / WID
+            self._style.figwidth = fig_w * 4.3 * self._scale * self._style.fs / 72 / WID
         self.figure.set_size_inches(self._style.figwidth, self._style.figwidth * fig_h / fig_w)
         if filename:
             self.figure.savefig(filename, dpi=self._style.dpi,
@@ -615,7 +614,7 @@ def _draw_regs_sub(self, n_fold, feedline_l=False, feedline_r=False):
                 label = qreg['label']
             y = qreg['y'] - n_fold * (self._cond['n_lines'] + 1)
             self.ax.text(self.x_offset - 0.2, y, label, ha='right', va='center',
-                         fontsize=1.25 * self._style.fs,
+                         fontsize=self._scale * 1.25 * self._style.fs,
                          color=self._style.tc,
                          clip_on=True,
                          zorder=PORDER_TEXT)
@@ -641,12 +640,12 @@ def _draw_regs_sub(self, n_fold, feedline_l=False, feedline_r=False):
                              zorder=PORDER_LINE)
                 self.ax.text(self.x_offset + 1.0, y + .1, str(this_creg['val']), ha='left',
                              va='bottom',
-                             fontsize=0.8 * self._style.fs,
+                             fontsize=self._scale * 0.8 * self._style.fs,
                              color=self._style.tc,
                              clip_on=True,
                              zorder=PORDER_TEXT)
             self.ax.text(self.x_offset - 0.2, y, this_creg['label'], ha='right', va='center',
-                         fontsize=1.5 * self._style.fs,
+                         fontsize=self._scale * 1.5 * self._style.fs,
                          color=self._style.tc,
                          clip_on=True,
                          zorder=PORDER_TEXT)
@@ -1093,7 +1092,7 @@ def _draw_ops(self, verbose=False):
                     x_coord = ii + 1
                     y_coord = 0.7
                 self.ax.text(x_coord, y_coord, str(ii + 1), ha='center',
-                             va='center', fontsize=self._style.sfs,
+                             va='center', fontsize=self._scale * self._style.sfs,
                              color=self._style.tc, clip_on=True,
                              zorder=PORDER_TEXT)
 

test/ipynb/mpl/test_circuit_matplotlib_drawer.py

@@ -21,7 +21,7 @@
 from qiskit.test import QiskitTestCase
 from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister
 from qiskit.visualization.circuit_visualization import _matplotlib_circuit_drawer
-
+from qiskit.quantum_info.random import random_unitary
 
 RESULTDIR = os.path.dirname(os.path.abspath(__file__))
 
@@ -138,6 +138,17 @@ def test_no_barriers_false(self):
 
         self.circuit_drawer(circuit, filename='no_barriers.png', plot_barriers=False)
 
+    def test_scale(self):
+        """Tests scale
+        See: https://github.com/Qiskit/qiskit-terra/issues/4179"""
+        circuit = QuantumCircuit(5)
+        circuit.unitary(random_unitary(2 ** 5), circuit.qubits)
+        circuit.draw('mpl')
+
+        self.circuit_drawer(circuit, filename='scale_default.png')
+        self.circuit_drawer(circuit, filename='scale_half.png', scale=0.5)
+        self.circuit_drawer(circuit, filename='scale_double.png', scale=2)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=1)

test/python/visualization/visualization.py

@@ -61,8 +61,8 @@ def assertImagesAreEqual(self, current, expected, diff_tolerance=0.001):
         similarity_ratio = black_pixels / total_pixels
         self.assertTrue(
             1 - similarity_ratio < diff_tolerance,
-            'The images are different by more than a {}%'
-            .format(diff_tolerance * 100))
+            'The images are different by {}%'.format((1 - similarity_ratio) * 100) +
+            ' which is more than the allowed {}%'.format(diff_tolerance * 100))
 
 
 def _get_black_pixels(image):