Is there OpenCV colormap in python?

Question

I am aware of Matlab, matplotlib style colormap in OpenCV . The documentation explains its usage for C++. I was wondering if such an option exists for python using cv2 as well. I googled a lot to find nothing. I am aware of matplotlib's colormap option that I can use but if cv2 provides such option, I can remove the overhead of converting the matplotlib colormaps to opencv images. Its clumsy. I require it for my project.

Answer 1

For OpenCV 2.4.11, applyColorMap works in Python (even though the 2.4.11 docs still list only C++):

import cv2
im = cv2.imread('test.jpg', cv2.IMREAD_GRAYSCALE)
imC = cv2.applyColorMap(im, cv2.COLORMAP_JET)

See also this Stack Overflow answer.

Answer 2

shame, it looks like it did not make it into the python api yet. but you could have a look at the implementation in modules/contrib/src/colormap.cpp, e.g. the jetmap is only a lookup-table, you could just steal it

Answer 3

Sadly OpenCV doesn't have any colorMap but you can write one. Not that difficult.

class ColorMap:
    startcolor = ()
    endcolor = ()
    startmap = 0
    endmap = 0
    colordistance = 0
    valuerange = 0
    ratios = []    

    def __init__(self, startcolor, endcolor, startmap, endmap):
        self.startcolor = np.array(startcolor)
        self.endcolor = np.array(endcolor)
        self.startmap = float(startmap)
        self.endmap = float(endmap)
        self.valuerange = float(endmap - startmap)
        self.ratios = (self.endcolor - self.startcolor) / self.valuerange

    def __getitem__(self, value):
        color = tuple(self.startcolor + (self.ratios * (value - self.startmap)))
        return (int(color[0]), int(color[1]), int(color[2]))