|
55 | 55 | print('viridis(np.linspace(0, 1, 15))', viridis(np.linspace(0, 1, 15))) |
56 | 56 |
|
57 | 57 | ############################################################################## |
58 | | -# Creating a new ListedColormap |
59 | | -# ============================= |
| 58 | +# Creating Listed colormaps |
| 59 | +# ========================= |
60 | 60 | # |
61 | 61 | # This is essential the inverse operation of the above where we supply a |
62 | 62 | # Nx4 numpy array with all values between 0 and 1, |
@@ -123,15 +123,18 @@ def plot_examples(cms): |
123 | 123 | plot_examples([viridis, newcmp]) |
124 | 124 |
|
125 | 125 | ############################################################################## |
126 | | -# LinearSegmented colormaps |
127 | | -# ========================= |
| 126 | +# Creating LinearSegmented colormaps |
| 127 | +# ================================== |
128 | 128 | # |
129 | | -# `.LinearSegmentedColormap` have an alternate way to specify colormaps that |
130 | | -# specify anchor points for linear ramps for each of RGB, and optionally, alpha |
131 | | -# (RGBA). |
| 129 | +# `.LinearSegmentedColormap` specify colormaps using anchor points |
| 130 | +# between which RGB(A) values are interpolated. |
132 | 131 | # |
133 | | -# The format to specify these colormaps is a bit complicated to allow |
134 | | -# discontinuities at the anchor points. First, with no discontinuities: |
| 132 | +# The format to specify these colormaps allows discontinuities at the anchor |
| 133 | +# points. Each anchor point is specified as a row in a matrix of the |
| 134 | +# form ``[x[i] yleft[i] yright[i]]``, where ``x[i]`` is the anchor, and |
| 135 | +# ``yleft[i]`` and ``yright[i]`` are the values of the color on either |
| 136 | +# side fo the anchor point. If there are no discontinuities, then |
| 137 | +# ``yleft[i]=yright[i]``: |
135 | 138 |
|
136 | 139 | cdict = {'red': [[0.0, 0.0, 0.0], |
137 | 140 | [0.5, 1.0, 1.0], |
@@ -161,14 +164,25 @@ def plot_linearmap(cdict): |
161 | 164 | plot_linearmap(cdict) |
162 | 165 |
|
163 | 166 | ############################################################################# |
164 | | -# However, consider the case where the third column is different than the |
165 | | -# second. The linear interpolation between red[i, 0] and red[i+1, 0] is |
166 | | -# from red[i, 2] to red[i+1, 1]. This format allows us to have |
167 | | -# discontinuities in the colormap at the anchor points; in this case |
168 | | -# between 0 and 0.5, the linear interpolation goes from 0.3 to 1, and |
169 | | -# between 0.5 and 1 it goes from 0.9 to 1. Note that red[0, 1], and red[2, 2] |
170 | | -# are both superfluous to the interpolation, which happens between the last |
171 | | -# element of the first anchor and the first element of the second anchor. |
| 167 | +# In order to make a discontinuity at an anchor point, the third column is |
| 168 | +# different than the second. The matrix for each or "red", "green", "blue", |
| 169 | +# and optionally "alpha" is set up as:: |
| 170 | +# |
| 171 | +# [... |
| 172 | +# [x[i] yleft[i] yright[i]], |
| 173 | +# [x[i+1] yleft[i+1] yright[i+1]] |
| 174 | +# ...] |
| 175 | +# |
| 176 | +# where the third column is the interpolation value |
| 177 | +# to the right of the anchor, and the second column the value to the left. |
| 178 | +# So, the linear interpolation between ``x[i]`` and |
| 179 | +# ``x[i+1]`` is from ``yright[i]`` to ``yleft[i+1] ``. |
| 180 | +# |
| 181 | +# In the example below there is a discontiuity in red at 0.5. The |
| 182 | +# interpolation between 0 and 0.5 goes from 0.3 to 1, and between 0.5 and 1 |
| 183 | +# it goes from 0.9 to 1. Note that red[0, 1], and red[2, 2] are both |
| 184 | +# superfluous to the interpolation because red[0, 1] is the value to the |
| 185 | +# left of 0, and red[2, 2] is the value to the right of 1.0. |
172 | 186 |
|
173 | 187 | cdict['red'] = [[0.0, 0.0, 0.3], |
174 | 188 | [0.5, 1.0, 0.9], |
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