In this article, we will see how we can set a color map to the image view object in PyQTGraph. 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. Color mapping is a function that maps the colors of one image to the colors of another image. A color mapping may be referred to as the algorithm that results in the mapping function or the algorithm that transforms the image colors.
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 setColorMap method with the image view object
Syntax : imv.setColorMap(cmap)
Argument : It takes ColorMap object as argument
Return : It returns None
Below is the implementation.
# importing Qt widgets from PyQt5.QtWidgets import *
# importing system import sys
# importing numpy as np import numpy as np
# importing pyqtgraph as pg import pyqtgraph as pg
from 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()
# setting fixed size of window
self .setFixedSize(QSize( 600 , 500 ))
# 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 ),
( 4 , 5 , 61 ),
( 84 , 42 , 55 ),
( 15 , 87 , 60 ),
( 208 , 17 , 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)
# create pyqt5 app App = QApplication(sys.argv)
# create the instance of our Window window = Window()
# start the app sys.exit(App. exec ())
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Output: