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Allow overriding scale and offset values #177

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merged 2 commits into from
Aug 15, 2024
Merged

Allow overriding scale and offset values #177

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beee318
Add test for overriding scale/offset
gerritholl Aug 8, 2024
f0d8d4c
Allow overriding scale and offset tag values
gerritholl Aug 8, 2024
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9 changes: 9 additions & 0 deletions trollimage/tests/test_image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2676,6 +2676,15 @@ def test_save_scale_offset_custom_labels(self):
expected_tags,
scale_offset_tags=("gradient", "axis_intercept"))

@pytest.mark.skipif(sys.platform.startswith('win'), reason="'NamedTemporaryFile' not supported on Windows")
def test_save_scale_offset_custom_values(self):
"""Test saving GeoTIFF overriding the scale/offset values."""
expected_tags = {"gradient": 1, "axis_intercept": 0}
self.img.stretch()
self._save_and_check_tags(
expected_tags,
scale_offset_tags={"gradient": 1, "axis_intercept": 0})


def _get_tags_after_writing_to_geotiff(data):
import rasterio as rio
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12 changes: 9 additions & 3 deletions trollimage/xrimage.py
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Original file line number Diff line number Diff line change
Expand Up @@ -305,7 +305,7 @@ def rio_save(self, filename, fformat=None, fill_value=None,
provided. Common values include `nearest` (default),
`bilinear`, `average`, and many others. See the rasterio
documentation for more information.
scale_offset_tags (Tuple[str, str] or None):
scale_offset_tags (Tuple[str, str] or Dict[str, number] or None):
If set to a ``(str, str)`` tuple, scale and offset will be
stored in GDALMetaData tags. Those can then be used to
retrieve the original data values from pixel values.
Expand All @@ -314,7 +314,9 @@ def rio_save(self, filename, fformat=None, fill_value=None,
represented by a simple scale and offset. Scale and offset
are also saved as (NaN, NaN) for multi-band images (ex. RGB)
as storing multiple values in a single GDALMetaData tag is not
currently supported.
currently supported. If set to a dictionary, automatically
determined scale/offset values are overruled by the values
provided in the keys.
colormap_tag (str or None):
If set and the image was colorized or palettized, a tag will
be added with this name with the value of a comma-separated
Expand Down Expand Up @@ -471,7 +473,11 @@ def pil_save(self, filename, fformat=None, fill_value=None,

def _add_scale_offset_to_tags(self, scale_offset_tags, data_arr, tags):
scale_label, offset_label = scale_offset_tags
scale, offset = self.get_scaling_from_history(data_arr.attrs.get('enhancement_history', []))
try:
scale = scale_offset_tags[scale_label]
offset = scale_offset_tags[offset_label]
except TypeError:
scale, offset = self.get_scaling_from_history(data_arr.attrs.get('enhancement_history', []))
tags[scale_label], tags[offset_label] = invert_scale_offset(scale, offset)

def get_scaling_from_history(self, history=None):
Expand Down
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