在pyqtgraph中更改散點圖plot colors的更有效方法

Question

背景：我正在創建一個 GUI，它將顯示 4 個六邊形像素的 arrays 中的更新當前值。 我認為最簡單的方法是在 pyqtgraph 中創建布局的分散 plot 並根據傳感器數據更新面部/畫筆顏色。

方法：我基本上抄襲了 pyqtgraph 示例腳本 ScatterPlotItem.py 和 ScatterPlotSpeedTest.py 並將它們調整到我的特定布局。

問題：性能非常慢，比我預期的要慢得多，因為示例 pyqtgraph 腳本以 1000+ fps 運行。 我的腳本目前以 ~4-7 fps 的速度運行。 這是相當令人驚訝的，因為我假設只改變一個點的顏色會很快。 我還在學習 pyqtgraph 並在 function update中使用ScatterPlotItem.setBrush() ，但它似乎很慢（我認為這是更新緩慢的根源）。 是否有更好/更快的方法來更新分散 plot 項目的面顏色？

這是我正在使用的腳本：

import numpy as np
import pyqtgraph as pg
from pyqtgraph.Qt import QtWidgets, QtCore
from time import perf_counter


# This function generates the hexgonal array x's and y's in the required ordering.
# It is ugly, but works for now.
def drawHexGridLoop2(origin, depth, apothem, padding):
    
    def getCoords(xs, ys):
        xs = [item for sublist in xs for item in sublist]
        ys = [item for sublist in ys for item in sublist]
        coords = list(zip(xs, ys))      
        return coords
    
    def flattenList(l):
        rv = [item for sublist in l for item in sublist]
        return rv
    
    ang60 = np.deg2rad(60)
    xs = [[origin[0]]]
    ys = [[origin[1]]]
    labels = [['1']]
    labelN = 2
    thisX = 0
    thisY = 0
    for d in range(1, depth):
        thisXArr = []
        thisYArr = []
        thisLabelArr = []
        loc = 1
        n=0
        while n < d*6:
            if n == 0:
                anchorN = 0
                thisX = round(xs[-1][0] + 2*apothem, 8)
                thisY = round(ys[-1][0], 8)
                anchorX = xs[-1][anchorN]
                anchorY = ys[-1][anchorN]
                thisXArr.append(thisX)
                thisYArr.append(thisY)
                thisLabelArr.append(str(labelN))
                labelN += 1

            else:
                thisX = round(anchorX + 2*apothem*np.cos(-1*ang60*loc), 8)
                thisY = round(anchorY + 2*apothem*np.sin(-1*ang60*loc), 8)
                if (thisX, thisY) in getCoords(xs, ys):
                    anchorN += 1
                    anchorX = xs[-1][anchorN]
                    anchorY = ys[-1][anchorN]
                    loc -= 1
                    continue
                thisXArr.append(thisX)
                thisYArr.append(thisY)
                thisLabelArr.append(str(labelN))
                labelN += 1
                loc += 1
            n += 1              
        xs.append(thisXArr)
        ys.append(thisYArr)
        labels.append(thisLabelArr)
    xs = flattenList(xs)
    ys = flattenList(ys)
    labels = flattenList(labels)
    return xs, ys, labels


# Function to create the scatter plot in each viewbox.
# Adapted from ScatterPlotItem.py
def createArray(w):
    s = pg.ScatterPlotItem(
        pxMode=False,  # Set pxMode=False to allow spots to transform with the view
        hoverable=True,
        hoverPen=pg.mkPen('g'),
        hoverSize=hexSize
    )
    spots = []
    xs, ys, labels = drawHexGridLoop2((0, 0), 14, 1e-6, 0)
    for i, thing in enumerate(xs):
        spots.append({'pos': (xs[i], ys[i]), 'size': hexSize, 'pen': {'color': 'w', 'width': 2}, 'brush':pg.intColor(10, 10), 'symbol':'h'})
    s.addPoints(spots)
    w.addItem(s)

    return w, s, spots, xs, ys

hexSize = 2.2e-6
app = pg.mkQApp("Scatter Plot Item Example") 
mw = QtWidgets.QMainWindow()
mw.resize(800,800)
view = pg.GraphicsLayoutWidget()  ## GraphicsView with GraphicsLayout inserted by default
mw.setCentralWidget(view)
mw.show()
mw.setWindowTitle('pyqtgraph example: ScatterPlot')
view.ci.setBorder((50, 50, 100))

## create four areas to add plots
w1 = view.addViewBox()
w1.setAspectLocked()
w2 = view.addViewBox()
w2.setAspectLocked()
view.nextRow()
w3 = view.addViewBox()
w3.setAspectLocked()
w4 = view.addViewBox()
w4.setAspectLocked()

# Create the scatter plots.
w1, s1, spots1, xs, ys = createArray(w1)
w2, s2, spots1, xs, ys = createArray(w2)
w3, s3, spots1, xs, ys = createArray(w3)
w4, s4, spots1, xs, ys = createArray(w4)

# Create the color map.
# Adapted from https://github.com/pyqtgraph/pyqtgraph/issues/1712#issuecomment-819745370
nPts = 255
colormap = pg.colormap.get('cividis')
valueRange = np.linspace(0, 255, num=nPts)
colors = colormap.getLookupTable(0, 1, nPts=nPts)

# This is really slow!
fps = None
lastTime = perf_counter()
def update():
    global fps, lastTime
    z = np.random.randint(0,255, size=547)
    brushes = colors[np.searchsorted(valueRange, z)]
    s1.setBrush(brushes) # Is there a faster way to do this?
    s2.setBrush(brushes)
    s3.setBrush(brushes)
    s4.setBrush(brushes)
    now = perf_counter()
    dt = now - lastTime
    lastTime = now
    if fps is None:
        fps = 1.0 / dt
    else:
        s = np.clip(dt * 3., 0, 1)
        fps = fps * (1 - s) + (1.0 / dt) * s
    mw.setWindowTitle('%0.2f fps' % fps)

    
timer = QtCore.QTimer()
timer.timeout.connect(update)
timer.start(0)

if __name__ == '__main__':
    pg.exec()

Answer 1

您的解決方案的問題是，您將 colors 數組傳遞給 setBrush 方法。 在這種情況下，PyqtGraph 必須為每一幀生成新的畫筆。 這是你的瓶頸。

為了加快速度，您可以創建畫筆表，其中將包含畫筆而不是 colors。 然后在更新 function 中，您只需生成索引數組並從中生成新的畫筆數組。 現在 PyqtGraph 將使用這些畫筆，而不是為每一幀創建一個新畫筆。
性能從約 7fps 提高到 35fps。

這是您修改后的示例：

import time

import numpy as np
import pyqtgraph as pg
from pyqtgraph.Qt import QtWidgets, QtCore, QtGui
from time import perf_counter


# This function generates the hexgonal array x's and y's in the required ordering.
# It is ugly, but works for now.
def drawHexGridLoop2(origin, depth, apothem, padding):
    def getCoords(xs, ys):
        xs = [item for sublist in xs for item in sublist]
        ys = [item for sublist in ys for item in sublist]
        coords = list(zip(xs, ys))
        return coords

    def flattenList(l):
        rv = [item for sublist in l for item in sublist]
        return rv

    ang60 = np.deg2rad(60)
    xs = [[origin[0]]]
    ys = [[origin[1]]]
    labels = [['1']]
    labelN = 2
    thisX = 0
    thisY = 0
    for d in range(1, depth):
        thisXArr = []
        thisYArr = []
        thisLabelArr = []
        loc = 1
        n = 0
        while n < d * 6:
            if n == 0:
                anchorN = 0
                thisX = round(xs[-1][0] + 2 * apothem, 8)
                thisY = round(ys[-1][0], 8)
                anchorX = xs[-1][anchorN]
                anchorY = ys[-1][anchorN]
                thisXArr.append(thisX)
                thisYArr.append(thisY)
                thisLabelArr.append(str(labelN))
                labelN += 1

            else:
                thisX = round(anchorX + 2 * apothem * np.cos(-1 * ang60 * loc), 8)
                thisY = round(anchorY + 2 * apothem * np.sin(-1 * ang60 * loc), 8)
                if (thisX, thisY) in getCoords(xs, ys):
                    anchorN += 1
                    anchorX = xs[-1][anchorN]
                    anchorY = ys[-1][anchorN]
                    loc -= 1
                    continue
                thisXArr.append(thisX)
                thisYArr.append(thisY)
                thisLabelArr.append(str(labelN))
                labelN += 1
                loc += 1
            n += 1
        xs.append(thisXArr)
        ys.append(thisYArr)
        labels.append(thisLabelArr)
    xs = flattenList(xs)
    ys = flattenList(ys)
    labels = flattenList(labels)
    return xs, ys, labels


# Function to create the scatter plot in each viewbox.
# Adapted from ScatterPlotItem.py
def createArray(w):
    s = pg.ScatterPlotItem(
        pxMode=False,  # Set pxMode=False to allow spots to transform with the view
        hoverable=True,
        hoverPen=pg.mkPen('g'),
        hoverSize=hexSize
    )
    spots = []
    xs, ys, labels = drawHexGridLoop2((0, 0), 14, 1e-6, 0)
    for i, thing in enumerate(xs):
        spots.append(
            {'pos': (xs[i], ys[i]), 'size': hexSize, 'pen': {'color': 'w', 'width': 2}, 'brush': pg.intColor(10, 10),
             'symbol': 'h'})
    s.addPoints(spots)
    w.addItem(s)

    return w, s, spots, xs, ys


hexSize = 2.2e-6
app = pg.mkQApp("Scatter Plot Item Example")
mw = QtWidgets.QMainWindow()
mw.resize(800, 800)
view = pg.GraphicsLayoutWidget()  ## GraphicsView with GraphicsLayout inserted by default
mw.setCentralWidget(view)
mw.show()
mw.setWindowTitle('pyqtgraph example: ScatterPlot')
view.ci.setBorder((50, 50, 100))

## create four areas to add plots
w1 = view.addViewBox()
w1.setAspectLocked()
w2 = view.addViewBox()
w2.setAspectLocked()
view.nextRow()
w3 = view.addViewBox()
w3.setAspectLocked()
w4 = view.addViewBox()
w4.setAspectLocked()

# Create the scatter plots.
w1, s1, spots1, xs, ys = createArray(w1)
w2, s2, spots1, xs, ys = createArray(w2)
w3, s3, spots1, xs, ys = createArray(w3)
w4, s4, spots1, xs, ys = createArray(w4)

# Create the color map.
# Adapted from https://github.com/pyqtgraph/pyqtgraph/issues/1712#issuecomment-819745370
nPts = 255
colormap = pg.colormap.get('cividis')
valueRange = np.linspace(0, 255, num=nPts)
colors = colormap.getLookupTable(0, 1, nPts=nPts)

# *** Create brushes lookup table
brushes_table = [QtGui.QBrush(QtGui.QColor(*color)) for color in colors]

fps = None
lastTime = perf_counter()


def update():
    global fps, lastTime
    z = np.random.randint(0, 255, size=547)
    # *** Create array of already created brushes from lookup table
    brushes = [brushes_table[i] for i in z]
    s1.setBrush(brushes)  # Now update is much faster!
    s2.setBrush(brushes)
    s3.setBrush(brushes)
    s4.setBrush(brushes)
    now = perf_counter()
    dt = now - lastTime
    lastTime = now
    if fps is None:
        fps = 1.0 / dt
    else:
        s = np.clip(dt * 3., 0, 1)
        fps = fps * (1 - s) + (1.0 / dt) * s
    mw.setWindowTitle('%0.2f fps' % fps)


timer = QtCore.QTimer()
timer.timeout.connect(update)
timer.start(0)

if __name__ == '__main__':
    pg.exec()