color transform for singleband and rgb

terracotta/handlers/rgb.py

@@ -111,18 +111,18 @@ def get_band_future(band_key: str) -> Future:
             out_ranges.append(band_stretch_range)
             out_arrays.append(band_data)
 
-    out = np.ma.stack(out_arrays, axis=0)
+    band_data = np.ma.stack(out_arrays, axis=0)
 
     if color_transform:
-        band_stretch_range_arr = [np.array(band_rng, dtype=band_data.dtype) for band_rng in out_ranges]
-        band_stretch_range_arr = np.ma.stack(band_stretch_range_arr, axis=0)
+        out_ranges = [np.array(band_rng, dtype=band_data.dtype) for band_rng in out_ranges]
+        out_ranges = np.ma.stack(out_ranges, axis=0)
 
-        band_stretch_range_arr = image.apply_color_transform(band_stretch_range_arr, color_transform)
-        band_data = image.apply_color_transform(out, color_transform)
+        out_ranges = image.apply_color_transform(out_ranges, color_transform, band_range)
+        band_data = image.apply_color_transform(band_data, color_transform, band_range)
 
     out_arrays = []
     for k in range(band_data.shape[0]):
-        out_arrays.append(image.to_uint8(band_data[k], *band_stretch_range_arr[k]))
+        out_arrays.append(image.to_uint8(band_data[k], *out_ranges[k]))
 
     out = np.ma.stack(out_arrays, axis=-1)
     return image.array_to_png(out)

terracotta/handlers/singleband.py

@@ -8,6 +8,8 @@
 
 import collections
 
+import numpy as np
+
 from terracotta import get_settings, get_driver, image, xyz
 from terracotta.profile import trace
 
@@ -26,6 +28,7 @@ def singleband(
     *,
     colormap: Union[str, Mapping[Number, RGBA], None] = None,
     stretch_range: Optional[Tuple[NumberOrString, NumberOrString]] = None,
+    color_transform: Optional[str] = None,
     tile_size: Optional[Tuple[int, int]] = None
 ) -> BinaryIO:
     """Return singleband image as PNG"""
@@ -73,6 +76,14 @@ def singleband(
 
         cmap_or_palette = cast(Optional[str], colormap)
 
+        if color_transform:
+            stretch_range_ = np.array(stretch_range_, dtype=tile_data.dtype)
+            stretch_range_ = np.ma.stack(stretch_range_, axis=0)
+
+            stretch_range_ = image.apply_color_transform(stretch_range_, color_transform, band_range)
+            tile_data = np.expand_dims(tile_data, axis=0)
+            tile_data = image.apply_color_transform(tile_data, color_transform, band_range)[0]
+
         out = image.to_uint8(tile_data, *stretch_range_)
 
     return image.array_to_png(out, colormap=cmap_or_palette)

terracotta/image.py

@@ -167,15 +167,21 @@ def to_uint8(data: Array, lower_bound: Number, upper_bound: Number) -> Array:
 def apply_color_transform(
         masked_data: Array,
         color_transform: str,
-        out_dtype: type = np.uint16,
+        band_range: list,
 ) -> Array:
     """Apply gamma correction to the input array and scale it to the output dtype."""
-    arr = to_math_type(masked_data)
+
+    if band_range:
+        arr = contrast_stretch(masked_data, band_range, (0, 1))
+    elif np.issubdtype(masked_data.dtype, np.integer):
+        arr = to_math_type(masked_data)
+    else:
+        raise exceptions.InvalidArgumentsError("No band range given and array is not of integer type")
+
 
     for func in parse_operations(color_transform):
         arr = func(arr)
 
-    arr = scale_dtype(arr, out_dtype)
     return arr
 
 

terracotta/server/fields.py

@@ -8,6 +8,8 @@
 
 from typing import Any, Union
 
+from color_operations import parse_operations
+
 
 class StringOrNumber(fields.Field):
     """
@@ -45,3 +47,19 @@ def validate_stretch_range(data: Any) -> None:
     if isinstance(data, str):
         if not re.match("^p\\d+$", data):
             raise ValidationError("Percentile format is `p<digits>`")
+
+
+def validate_color_transform(data: Any) -> None:
+    """
+    Validate that the color transform is a string and can be parsed by `color_operations`.
+    """
+    if not isinstance(data, str):
+        raise ValidationError("Color transform needs to be a string")
+
+    if "saturation" in data:
+        raise ValidationError("Saturation is currently not supported")
+
+    try:
+        parse_operations(data)
+    except (ValueError, KeyError):
+        raise ValidationError("Invalid color transform")

terracotta/server/rgb.py

@@ -9,7 +9,7 @@
 from marshmallow import Schema, fields, validate, pre_load, ValidationError, EXCLUDE
 from flask import request, send_file, Response
 
-from terracotta.server.fields import StringOrNumber, validate_stretch_range
+from terracotta.server.fields import StringOrNumber, validate_stretch_range, validate_color_transform
 from terracotta.server.flask_api import TILE_API
 
 
@@ -69,8 +69,9 @@ class Meta:
         ),
     )
     color_transform = fields.String(
+        validate=validate_color_transform,
         missing=None,
-        description="Gamma factor to perform gamma correction."
+        description="Color transform DSL string from color-operations.",
     )
     tile_size = fields.List(
         fields.Integer(),

terracotta/server/singleband.py

@@ -17,7 +17,7 @@
 )
 from flask import request, send_file, Response
 
-from terracotta.server.fields import StringOrNumber, validate_stretch_range
+from terracotta.server.fields import StringOrNumber, validate_stretch_range, validate_color_transform
 from terracotta.server.flask_api import TILE_API
 from terracotta.cmaps import AVAILABLE_CMAPS
 
@@ -65,6 +65,14 @@ class Meta:
         "hex strings.",
     )
 
+    color_transform = fields.String(
+        validate=validate_color_transform,
+        missing=None,
+        example="gamma 1 1.5, sigmoidal 1 15 0.5",
+        description="Color transform DSL string from color-operations."
+        "All color operations for singleband should specify band 1.",
+    )
+
     tile_size = fields.List(
         fields.Integer(),
         validate=validate.Length(equal=2),