问题
I use pyqtgraph for data acquisition and I have to represent some thresholds on the graphics view. For example to represent a high voltage limit, etc.
I used the class InfiniteLine from pyqtgraph, but now, I have to take into account some possible changes on the threshold value during the acquisition. It would look as a step between two infinite line (please find an example attached).
example
For this, I would have to draw a half infinite line. Do you know a simple way to do it?
I thought about using some plotCurveItem limited by the viewBox minimum and maximum :
thresholdValue = 60V # just an example
range = self.viewBox.viewRange()
xRange = range[0] # we only want ViewBox horizontal limits
minView = xRange[0]
maxView = xRange[1]
myPlotCurveItem = pyqtgraph.PlotCurveItem([minView, maxView],[thresholdValue, thresholdValue])
In case of changing on threshold value :
newThresholdValue = 70V
the x data for the plotCurveItem would become :
[minView, changingTime] #with changinTime : the moment we change the threshold
and we would add a new plotCurveItem :
myNewPlotCurveItem = pyqtgraph.plotCurveItem([changingTime, maxView],[newThresholdValue, newThresholdValue])
Does this solution looks good or do you see any problem with that?
回答1:
Your approach looks good and is mostly what pyqtgraph.InfiniteLine is doing. I examined the source of InfiniteLine and extracted those parts which are absolutely necessary and added the change point and two level information, then drawing three lines (left border to change point at left level, change point to right border at right level, connection of both).
Here is the full code:
from pyqtgraph.Qt import QtGui
import numpy as np
import pyqtgraph as pg
class InfiniteLineWithBreak(pg.GraphicsObject):
def __init__(self, changeX, levelsY, pen=None):
pg.GraphicsObject.__init__(self)
self.changeX = changeX
self.levelsY = levelsY
self.maxRange = [None, None]
self.moving = False
self.movable = False
self.mouseHovering = False
pen = (200, 200, 100)
self.setPen(pen)
self.setHoverPen(color=(255,0,0), width=self.pen.width())
self.currentPen = self.pen
def setBounds(self, bounds):
self.maxRange = bounds
self.setValue(self.value())
def setPen(self, *args, **kwargs):
self.pen = pg.fn.mkPen(*args, **kwargs)
if not self.mouseHovering:
self.currentPen = self.pen
self.update()
def setHoverPen(self, *args, **kwargs):
self.hoverPen = pg.fn.mkPen(*args, **kwargs)
if self.mouseHovering:
self.currentPen = self.hoverPen
self.update()
def boundingRect(self):
br = self.viewRect()
return br.normalized()
def paint(self, p, *args):
br = self.boundingRect()
p.setPen(self.currentPen)
# three lines (left border to change point, change point vertical, change point to right)
p.drawLine(pg.Point(br.left(), self.levelsY[0]), pg.Point(self.changeX, self.levelsY[0]))
p.drawLine(pg.Point(self.changeX, self.levelsY[0]), pg.Point(self.changeX, self.levelsY[1]))
p.drawLine(pg.Point(self.changeX, self.levelsY[1]), pg.Point(br.right(), self.levelsY[1]))
def dataBounds(self, axis, frac=1.0, orthoRange=None):
if axis == 0:
return None ## x axis should never be auto-scaled
else:
return (0,0)
def setMouseHover(self, hover):
pass
app = QtGui.QApplication([])
w = pg.GraphicsWindow()
w.resize(1000, 600)
v = w.addPlot(y=np.random.normal(size=100))
v.addItem(InfiniteLineWithBreak(changeX=50, levelsY=(-1, 1)))
app.exec_()
It looks like:
What one could add is reaction to hovering and changing the values with the mouse (change point as well as levels) or even rotate by 90 degree. InfiniteLine is a good example of how to do that.
回答2:
thanks you for you very complete answer ! Your code works very well. I made some modifications on your class InfiniteLineWithBreak in order to set multiple threshold transitions. I modified the init and the paint methods only:
def __init__(self, listOfcouplesOfThresholdAndItsDate, pen=None):
pg.GraphicsObject.__init__(self)
self.listOfcouplesOfThresholdAndItsDate=listOfcouplesOfThresholdAndItsDate
self.maxRange = [None, None]
self.moving = False
self.movable = False
self.mouseHovering = False
pen = (200, 200, 100)
self.setPen(pen)
self.setHoverPen(color=(255,0,0), width=self.pen.width())
self.currentPen = self.pen
def paint(self, p, *args):
br = self.boundingRect()
p.setPen(self.currentPen)
if len(self.listOfcouplesOfThresholdAndItsDate)==0:
pass
elif len(self.listOfcouplesOfThresholdAndItsDate)==1:
threshold = self.listOfcouplesOfThresholdAndItsDate[0][1]
date = self.listOfcouplesOfThresholdAndItsDate[0][0]
p.drawLine(pg.Point(date, threshold), pg.Point(br.right(), threshold))
else:
threshold = self.listOfcouplesOfThresholdAndItsDate[0][1]
date = self.listOfcouplesOfThresholdAndItsDate[0][0]
i=0
for i in range(0, len(self.listOfcouplesOfThresholdAndItsDate)-2):
threshold = self.listOfcouplesOfThresholdAndItsDate[i][1]
date = self.listOfcouplesOfThresholdAndItsDate[i][0]
nexteDate = self.listOfcouplesOfThresholdAndItsDate[i+1][0]
nextThreshold = self.listOfcouplesOfThresholdAndItsDate[i+1][1]
p.drawLine(pg.Point(date, threshold), pg.Point(nexteDate, threshold))
p.drawLine(pg.Point(nexteDate, threshold), pg.Point(nexteDate, nextThreshold))
threshold = self.listOfcouplesOfThresholdAndItsDate[-2][1]
date = self.listOfcouplesOfThresholdAndItsDate[-2][0]
nexteDate = self.listOfcouplesOfThresholdAndItsDate[-1][0]
nextThreshold = self.listOfcouplesOfThresholdAndItsDate[-1][1]
p.drawLine(pg.Point(date, threshold), pg.Point(nexteDate, threshold))
p.drawLine(pg.Point(nexteDate, threshold), pg.Point(nexteDate, nextThreshold))
p.drawLine(pg.Point(nexteDate, nextThreshold), pg.Point(br.right(), nextThreshold))
Moreover, I added a method to append a new threshold transition point to the listOfcouplesOfThersholdAndItsDate :
def addANewThreshold(self,date, threshold):
self.listOfcouplesOfThresholdAndItsDate.append((date, threshold))
Here is an example of what it looks like : example of multiple thresholds
Does the code look okay to you ? Thank you,
来源：https://stackoverflow.com/questions/37702642/draw-half-infinite-lines