ENH: Add measure tool plugin

skimage/viewer/plugins/measure.py

@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+import numpy as np
+
+from .base import Plugin
+from ..widgets import Text
+from ..canvastools import LineTool
+
+
+__all__ = ['Measure']
+
+
+rad2deg = 180 / np.pi
+
+
+class Measure(Plugin):
+    name = 'Measure'
+    draws_on_image = True
+
+    def __init__(self, maxdist=10, **kwargs):
+        super(Measure, self).__init__(**kwargs)
+
+        self.maxdist = maxdist
+        self._length = Text('Length:')
+        self._angle = Text('Angle:')
+
+        self.add_widget(self._length)
+        self.add_widget(self._angle)
+
+        print self.help()
+
+    def attach(self, image_viewer):
+        super(Measure, self).attach(image_viewer)
+
+        image = image_viewer.original_image
+        h, w = image.shape
+        x = [w / 3, 2 * w / 3]
+        y = [h / 2] * 2
+        self.line_tool = LineTool(self.image_viewer.ax, x, y,
+                                  maxdist=self.maxdist,
+                                  on_update=self.line_changed)
+        # initialize displayed values
+        self.line_changed(np.transpose((x, y)))
+
+    def help(self):
+        helpstr = ("Line profile tool",
+                   "Select line to measure distance and angle.")
+        return '\n'.join(helpstr)
+
+    def line_changed(self, end_pts):
+        x, y = np.transpose(end_pts)
+        dx = np.diff(x)[0]
+        dy = np.diff(y)[0]
+        self._length.text = '%.1f' % np.hypot(dx, dy)
+        self._angle.text = u'%.1f°' % (180 - np.arctan2(dy, dx) * rad2deg)

skimage/viewer/widgets/core.py

@@ -27,7 +27,7 @@ except ImportError:
 from ..utils import RequiredAttr
 
 
-__all__ = ['BaseWidget', 'Slider', 'ComboBox']
+__all__ = ['BaseWidget', 'Slider', 'ComboBox', 'Text']
 
 
 class BaseWidget(QWidget):
@@ -50,6 +50,29 @@ class BaseWidget(QWidget):
         self.callback(self.name, value)
 
 
+class Text(BaseWidget):
+
+    def __init__(self, name=None, text=''):
+        super(Text, self).__init__(name)
+        self._label = QtGui.QLabel()
+        self.text = text
+        self.layout = QtGui.QHBoxLayout(self)
+        if name is not None:
+            name_label = QtGui.QLabel()
+            name_label.setText(name)
+            self.layout.addWidget(name_label)
+        self.layout.addWidget(self._label)
+
+
+    @property
+    def text(self):
+        return self._label.text()
+
+    @text.setter
+    def text(self, text_str):
+        self._label.setText(text_str)
+
+
 class Slider(BaseWidget):
     """Slider widget for adjusting numeric parameters.