Reverse colormap in matplotlib

Question

I would like to know how to simply reverse the color order of a given colormap in order to use it with plot surface

User · Answer

As of Matplotlib 2 0  there is a reversed   method for ListedColormap and LinearSegmentedColorMap objects  so you can just do  cmap reversed   cmap reversed     Here is the documentation

User · Answer

The standard colormaps also all have reversed versions  They have the same names with  r tacked on to the end   Documentation here

User · Answer

There is no built-in way  yet  of reversing arbitrary colormaps  but one simple solution is to actually not modify the colorbar but to create an inverting Normalize object   from matplotlib colors import Normalize  class InvertedNormalize Normalize       def   call   self   args    kwargs           return 1 - super InvertedNormalize  self    call    args    kwargs    You can then use this with plot surface and other Matplotlib plotting functions by doing e g   inverted norm   InvertedNormalize vmin 10  vmax 100  ax plot surface      cmap  lt your colormap gt   norm inverted norm    This will work with any Matplotlib colormap

User · Answer

In matplotlib a color map isn t a list  but it contains the list of its colors as colormap colors  And the module matplotlib colors provides a function ListedColormap   to generate a color map from a list  So you can reverse any color map by doing   colormap r   ListedColormap colormap colors   -1

User · Answer

The solution is pretty straightforward  Suppose you want to use the  autumn  colormap scheme  The standard version   cmap   matplotlib cm autumn   To reverse the colormap color spectrum  use get cmap   function and append   r  to the colormap title like this   cmap reversed   matplotlib cm get cmap  autumn r

User · Answer

There are two types of LinearSegmentedColormaps  In some  the  segmentdata is given explicitly  e g   for jet    gt  gt  gt  cm jet  segmentdata   blue     0 0  0 5  0 5    0 11  1  1    0 34  1  1    0 65  0  0    1  0  0     red     0 0  0  0    0 35  0  0    0 66  1  1    0 89  1  1    1  0 5  0 5     green     0 0  0  0    0 125  0  0    0 375  1  1    0 64  1  1    0 91  0  0    1  0  0      For rainbow   segmentdata is given as follows    gt  gt  gt  cm rainbow  segmentdata   blue    lt function  lt lambda gt  at 0x7fac32ac2b70 gt    red    lt function  lt lambda gt  at 0x7fac32ac7840 gt    green    lt function  lt lambda gt  at 0x7fac32ac2d08 gt     We can find the functions in the source of matplotlib  where they are given as   rainbow data              red   gfunc 33       33  lambda x  np abs 2   x - 0 5            green   gfunc 13     13  lambda x  np sin x   np pi            blue   gfunc 10      10  lambda x  np cos x   np pi   2      Everything you want is already done in matplotlib  just call cm revcmap  which reverses both types of segmentdata  so  cm revcmap cm rainbow  segmentdata    should do the job - you can simply create a new LinearSegmentData from that  In revcmap  the reversal of function based SegmentData is done with  def  reverser f       def freversed x           return f 1 - x      return freversed   while the other lists are reversed as usual  valnew     1 0 - x  y1  y0  for x  y0  y1 in reversed val      So actually the whole thing you want  is  def reverse colourmap cmap  name    my cmap r         return mpl colors LinearSegmentedColormap name  cm revcmap cmap  segmentdata

User · Answer

As a LinearSegmentedColormaps is based on a dictionary of red  green and blue  it s necessary to reverse each item   import matplotlib pyplot as plt import matplotlib as mpl def reverse colourmap cmap  name    my cmap r                In       cmap  name      Out      my cmap r      Explanation      t 0  goes from 0 to 1     row i    x  y0  y1 - gt  t 0  t 1  t 2                                               row i 1  x  y0  y1 - gt  t n  t 1  t 2       so the inverse should do the same      row i 1  x  y1  y0 - gt  1-t 0  t 2  t 1                                               row i    x  y1  y0 - gt  1-t n  t 2  t 1                      reverse          k              for key in cmap  segmentdata              k append key          channel   cmap  segmentdata key          data               for t in channel                                  data append  1-t 0  t 2  t 1                        reverse append sorted data            LinearL   dict zip k reverse       my cmap r   mpl colors LinearSegmentedColormap name  LinearL       return my cmap r   See that it works   my cmap          lt matplotlib colors LinearSegmentedColormap at 0xd5a0518 gt   my cmap r   reverse colourmap my cmap   fig   plt figure figsize  8  2   ax1   fig add axes  0 05  0 80  0 9  0 15   ax2   fig add axes  0 05  0 475  0 9  0 15   norm   mpl colors Normalize vmin 0  vmax 1  cb1   mpl colorbar ColorbarBase ax1  cmap   my cmap  norm norm orientation  horizontal   cb2   mpl colorbar ColorbarBase ax2  cmap   my cmap r  norm norm  orientation  horizontal       EDIT    I don t get the comment of user3445587  It works fine on the rainbow colormap   cmap   mpl cm jet cmap r   reverse colourmap cmap   fig   plt figure figsize  8  2   ax1   fig add axes  0 05  0 80  0 9  0 15   ax2   fig add axes  0 05  0 475  0 9  0 15   norm   mpl colors Normalize vmin 0  vmax 1  cb1   mpl colorbar ColorbarBase ax1  cmap   cmap  norm norm orientation  horizontal   cb2   mpl colorbar ColorbarBase ax2  cmap   cmap r  norm norm  orientation  horizontal       But it especially works nice for custom declared colormaps  as there is not a default  r for custom declared colormaps  Following example taken from http   matplotlib org examples pylab examples custom cmap html   cdict1     red       0 0  0 0  0 0                       0 5  0 0  0 1                       1 0  1 0  1 0               green     0 0  0 0  0 0                       1 0  0 0  0 0               blue      0 0  0 0  1 0                       0 5  0 1  0 0                       1 0  0 0  0 0               blue red1   mpl colors LinearSegmentedColormap  BlueRed1   cdict1  blue red1 r   reverse colourmap blue red1   fig   plt figure figsize  8  2   ax1   fig add axes  0 05  0 80  0 9  0 15   ax2   fig add axes  0 05  0 475  0 9  0 15    norm   mpl colors Normalize vmin 0  vmax 1  cb1   mpl colorbar ColorbarBase ax1  cmap   blue red1  norm norm orientation  horizontal   cb2   mpl colorbar ColorbarBase ax2  cmap   blue red1 r  norm norm  orientation  horizontal

[python] Reverse colormap in matplotlib

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