PyQtGraph – Getting Histogram Object for Image View

25 May, 2022
In this article, we will see how we can get the histogram object of the image view object in PyQTGaph. PyQtGraph is a graphics and user interface library for Python that provides functionality commonly required in designing and science applications. Its primary goals are to provide fast, interactive graphics for displaying data (plots, video, etc.). Widget used for display and analysis of image data. Implements many features like displaying 2D and 3D image data. For 3D data, a z-axis slider is displayed allowing the user to select which frame is displayed. Displays histogram of image data with movable region defining the dark/light levels, editable gradient provides a color lookup table, frame slider may also be moved using left/right arrow keys as well as pgup, pgdn, home, and end. A histogram is a graphical display of data using bars of different heights. In a histogram, each bar group numbers into ranges. Taller bars show that more data falls in that range.We can create an image view with the help of the command given below.
# creating a pyqtgraph image view object
imv = pg.ImageView()
In order to do this we use getHistogramWidget method with the image view objectSyntax : imv.getHistogramWidget()Argument : It takes no argumentReturn : It returns HistogramLUTWidget object 
Below is the implementation.
Python3
# importing Qt widgetsfrom PyQt5.QtWidgets import * # importing systemimport sys # importing numpy as npimport numpy as np # importing pyqtgraph as pgimport pyqtgraph as pgfrom PyQt5.QtGui import *from PyQt5.QtCore import * from collections import namedtuple  class Window(QMainWindow):     def __init__(self):        super().__init__()         # setting title        self.setWindowTitle("PyQtGraph")         # setting geometry        self.setGeometry(100, 100, 600, 500)         # icon        icon = QIcon("skin.png")         # setting icon to the window        self.setWindowIcon(icon)         # calling method        self.UiComponents()         # showing all the widgets        self.show()     # method for components    def UiComponents(self):         # creating a widget object        widget = QWidget()         # creating a label        label = QLabel("Geeksforgeeks Image View")         # setting minimum width        label.setMinimumWidth(130)         # making label do word wrap        label.setWordWrap(True)         # setting configuration options        pg.setConfigOptions(antialias=True)         # creating image view object        imv = pg.ImageView()         # Create random 3D data set with noisy signals        img = pg.gaussianFilter(np.random.normal(            size=(200, 200)), (5, 5)) * 20 + 100         # setting new axis to image        img = img[np.newaxis, :, :]         # decay data        decay = np.exp(-np.linspace(0, 0.3, 100))[:, np.newaxis, np.newaxis]         # random data        data = np.random.normal(size=(100, 200, 200))        data += img * decay        data += 2         # adding time-varying signal        sig = np.zeros(data.shape[0])        sig[30:] += np.exp(-np.linspace(1, 10, 70))        sig[40:] += np.exp(-np.linspace(1, 10, 60))        sig[70:] += np.exp(-np.linspace(1, 10, 30))         sig = sig[:, np.newaxis, np.newaxis] * 3        data[:, 50:60, 30:40] += sig         # Displaying the data and assign each frame a time value from 1.0 to 3.0        imv.setImage(data, xvals=np.linspace(1., 3., data.shape[0]))         # Set a custom color map        colors = [            (0, 0, 0),            (45, 5, 61),            (84, 42, 55),            (150, 87, 60),            (208, 171, 141),            (255, 255, 255)        ]         # color map        cmap = pg.ColorMap(pos=np.linspace(0.0, 1.0, 6), color=colors)         # setting color map to the image view        imv.setColorMap(cmap)         # Creating a grid layout        layout = QGridLayout()         # minimum width value of the label        label.setFixedWidth(130)         # setting this layout to the widget        widget.setLayout(layout)         # adding label in the layout        layout.addWidget(label, 1, 0)         # plot window goes on right side, spanning 3 rows        layout.addWidget(imv, 0, 1, 3, 1)         # setting this widget as central widget of the main window        self.setCentralWidget(widget)         # getting histogram object from image view        value = imv.getHistogramWidget()         # setting text to the label        label.setText("Histogram Widget : " + str(value))  # create pyqt5 appApp = QApplication(sys.argv) # create the instance of our Windowwindow = Window() # start the appsys.exit(App.exec())
Output :  
 
sweetyty
Python-gui
Python-PyQtGraph
Python
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