OpenCV – Image Filters - Techie Vaibhav

Hello Guys,

In this tutorial, I will discuss the color map in OpenCV. Color Map is used to show different color temperatures. And this can also be used to generate some cool image filters.

OpenCV comes with thirteen built-in color maps. So in this tutorial, I will show you how to use color maps.

Let’s get started

List of Color Maps

COLORMAP_AUTUMN

COLORMAP_BONE

COLORMAP_JET

COLORMAP_WINTER

COLORMAP_RAINBOW

COLORMAP_OCEAN

COLORMAP_SUMMER

COLORMAP_SPRING

COLORMAP_COOL

COLORMAP_HSV

COLORMAP_PINK

COLORMAP_HOT

COLORMAP_PARULA

To apply color map first we need to convert an image to grayscale. So I will use

img = cv.imread("nature.jpg",cv.IMREAD_GRAYSCALE)

If you are not aware of this function then please check my previous tutorial http://techievaibhav.in/2019/01/10/reading-an-image-using-opencv/

To apply color maps, OpenCV comes with a function called applyColorMap(). This function takes two parameters.

Gray Scale image
Color Map

Program

#import cv2 module
import cv2 as cv

def showImage(effect,image):
    cv.imshow(effect,image)
    cv.waitKey(0)
    cv.destroyAllWindows()
    
img_gray = cv.imread("nature.jpg",cv.IMREAD_GRAYSCALE)

img = cv.applyColorMap(img_gray,cv.COLORMAP_AUTUMN)
showImage("autumn",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_BONE)
showImage("Bone",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_JET)
showImage("jet",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_WINTER)
showImage("Winter",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_RAINBOW)
showImage("Rainbow",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_OCEAN)
showImage("Ocean",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_SUMMER)
showImage("Summer",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_SPRING)
showImage("Spring",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_COOL)
showImage("Cool",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_HSV)
showImage("HSV",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_PINK)
showImage("Pink",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_HOT)
showImage("Hot",img)

img = cv.applyColorMap(img_gray,cv.COLORMAP_PARULA)
showImage("Parula",img)

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