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apply discrete cmap when needed #325

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Dec 22, 2020
Merged

apply discrete cmap when needed #325

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3 changes: 3 additions & 0 deletions rio_tiler/colormap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,9 @@ def apply_cmap(
if data.shape[0] > 1:
raise InvalidFormat("Source data must be 1 band")

if len(colormap) > 256 or max(colormap) > 256:
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Why do you only check for > 256 and not != 256?

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@vincentsarago vincentsarago Dec 23, 2020 •
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@kylebarron because make_lut should work for cmap that have less than 256 value or a max smaller than 256
https://github.com/cogeotiff/rio-tiler/pull/325/files#diff-1c0d3ee98487c3ad9e96a708cf2b17d8dba80980c2b0bd6faaca3688543bfd41R66-R68

just realizing that it should be max(colormap) >= 256 🤦

e.g

cmap = {1: [255,255,255,255], 255: [1,1,1, 255]}
make_lut(cmap)
array([[  0,   0,   0,   0],
       [255, 255, 255, 255],
       [  0,   0,   0,   0],
       ...,
       [  0,   0,   0,   0],
       [  0,   0,   0,   0],
       [  1,   1,   1, 255]], dtype=uint8)

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updated the code with comments: https://github.com/cogeotiff/rio-tiler/blob/master/rio_tiler/colormap.py#L97-L101

return apply_discrete_cmap(data, colormap)

lookup_table = make_lut(colormap)
data = lookup_table[data[0], :]

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15 changes: 15 additions & 0 deletions tests/test_cmap.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
"""tests rio_tiler colormaps"""

from copy import deepcopy

import numpy
import pytest

Expand Down Expand Up @@ -141,3 +143,16 @@ def test_apply_discrete_cmap():
mask[2:5, 2:5] = 255
mask[5:, 5:] = 255
numpy.testing.assert_array_equal(m, mask)

cm = {1: [0, 0, 0, 255], 1000: [255, 255, 255, 255]}
d, m = colormap.apply_cmap(data, cm)
dd, mm = colormap.apply_discrete_cmap(data, cm)
numpy.testing.assert_array_equal(dd, d)
numpy.testing.assert_array_equal(mm, m)

cm = deepcopy(colormap.EMPTY_COLORMAP)
cm.pop(255)
cm[1000] = [255, 255, 255, 255]

d, m = colormap.apply_cmap(data, cm)
dd, mm = colormap.apply_discrete_cmap(data, cm)