Load style for raster layers

src/qgis_geonode/sldconverter.py

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+"""Utilities to convert styles between OGC SLD and QGIS QML"""
+
+import typing
+import xml.etree.ElementTree as ET
+from xml.dom import minidom
+
+import qgis.core
+from qgis.PyQt import QtXml
+
+
+def convert_sld_to_qml(raw_sld: str) -> str:
+    """Convert SLD to QGIS QML style.
+
+    This code is an modification of the ``SLD4raster.sld2qml()`` method, as found on the
+    SLD4raster QGIS plugin:
+
+    https://github.com/MSBilgin/SLD4raster
+
+    Originally created by Mehmet Selim BILGIN. Original code was published with
+    GPL v2 license.
+
+    """
+
+    sld_document = minidom.parseString(raw_sld)
+    if len(sld_document.getElementsByTagName("sld:RasterSymbolizer")) > 0:
+        ns = "sld:"
+    elif len(sld_document.getElementsByTagName("se:RasterSymbolizer")) > 0:
+        ns = "se:"
+    else:
+        ns = ""
+    root_el = ET.Element("qgis")
+    pipe_el = ET.SubElement(root_el, "pipe")
+    raster_renderer_el = ET.SubElement(pipe_el, "rasterrenderer")
+    ET.SubElement(raster_renderer_el, "rasterTransparency")
+    colormap_el_list = sld_document.getElementsByTagName(f"{ns}ColorMap")
+    is_singleband = len(colormap_el_list) > 0
+    if is_singleband:
+        raster_renderer_el.attrib["type"] = "singlebandpseudocolor"
+        raster_renderer_el.attrib["band"] = "1"
+        raster_shader_el = ET.SubElement(raster_renderer_el, "rastershader")
+        color_ramp_shader_el = ET.SubElement(raster_shader_el, "colorrampshader")
+        try:
+            # Sometimes "ColorMap" tag does not contain "type" attribute. This means
+            # it is a ramp color.
+            color_map_el = sld_document.getElementsByTagName(f"{ns}ColorMap")[0]
+            sld_color_map_type = color_map_el.attributes.has_key("type")
+            # or getting raster map colortype by "type" atribute.
+            sld_color_map_type2 = color_map_el.attributes["type"].value
+            if sld_color_map_type and sld_color_map_type2 == "intervals":
+                color_ramp_shader_el.attrib["colorRampType"] = "DISCRETE"
+        except Exception:
+            color_ramp_shader_el.attrib["colorRampType"] = "INTERPOLATED"
+        for color_map_entry in sld_document.getElementsByTagName(f"{ns}ColorMapEntry"):
+            try:
+                label = color_map_entry.attributes["label"].value
+            except Exception:
+                label = color_map_entry.attributes["quantity"].value
+            item_el = ET.SubElement(color_ramp_shader_el, "item")
+            item_el.attrib["alpha"] = "255"
+            item_el.attrib["value"] = color_map_entry.attributes["quantity"].value
+            item_el.attrib["label"] = label
+            item_el.attrib["color"] = color_map_entry.attributes["color"].value
+    else:
+        red_channel_el = sld_document.getElementsByTagName(f"{ns}RedChannel")[0]
+        red_band = red_channel_el.getElementsByTagName(
+            f"{ns}SourceChannelName"
+        ).firstChild.nodeValue
+        green_channel_el = sld_document.getElementsByTagName(f"{ns}GreenChannel")[0]
+        green_band = green_channel_el.getElementsByTagName(
+            f"{ns}SourceChannelName"
+        ).firstChild.nodeValue
+        blue_channel_el = sld_document.getElementsByTagName(f"{ns}BlueChannel")[0]
+        blue_band = blue_channel_el.getElementsByTagName(
+            f"{ns}SourceChannelName"
+        ).firstChild.nodeValue
+        raster_renderer_el.attrib["type"] = "multibandcolor"
+        raster_renderer_el.attrib["redBand"] = red_band
+        raster_renderer_el.attrib["greenBand"] = green_band
+        raster_renderer_el.attrib["blueBand"] = blue_band
+
+    try:
+        # some SLD documents don't have 'Opacity' tag
+        sld_opacity = sld_document.getElementsByTagName(f"{ns}Opacity")[
+            0
+        ].firstChild.nodeValue
+    except Exception:
+        sld_opacity = "1"
+
+    raster_renderer_el.attrib["opacity"] = sld_opacity
+    ET.SubElement(pipe_el, "brightnesscontrast")
+    ET.SubElement(pipe_el, "huesaturation")
+    ET.SubElement(pipe_el, "rasterresampler")
+    blend_mode_el = ET.SubElement(root_el, "blendMode")
+    blend_mode_el.text = "0"
+    return ET.tostring(root_el).decode("utf-8")
+
+
+def get_qml(layer: qgis.core.QgsMapLayer) -> typing.Tuple[str, typing.Optional[str]]:
+    qml_document = QtXml.QDomDocument()
+    root = qml_document.createElement("SLD4raster")
+    qml_document.appendChild(root)
+    qgis_node = qml_document.createElement("qgis")
+    root.appendChild(qgis_node)
+    error_message = None
+    context = qgis.core.QgsReadWriteContext()
+    layer.writeSymbology(qgis_node, qml_document, error_message, context)
+    return qml_document.toString(), error_message
+
+
+def convert_qml_to_sld(raw_qml: str, sld_name: str) -> str:
+    """Convert QGIS QML style to SLD
+
+    This code is an modification of the ``SLD4raster.qml2sld()`` method, as found on the
+    SLD4raster QGIS plugin:
+
+    https://github.com/MSBilgin/SLD4raster
+
+    Originally created by Mehmet Selim BILGIN. Original code was published with
+    GPL v2 license.
+
+    """
+
+    root_el = ET.Element("sld:StyledLayerDescriptor")
+    root_el.attrib["xmlns"] = "http://www.opengis.net/sld"
+    root_el.attrib["xmlns:sld"] = "http://www.opengis.net/sld"
+    root_el.attrib["xmlns:ogc"] = "http://www.opengis.net/ogc"
+    root_el.attrib["xmlns:gml"] = "http://www.opengis.net/gml"
+    root_el.attrib["version"] = "1.0.0"
+    user_layer_el = ET.SubElement(root_el, "sld:UserLayer")
+    layer_feature_constraints_el = ET.SubElement(
+        user_layer_el, "sld:LayerFeatureConstraints"
+    )
+    ET.SubElement(layer_feature_constraints_el, "sld:FeatureTypeConstraint")
+    user_style_el = ET.SubElement(user_layer_el, "sld:UserStyle")
+    style_name_el = ET.SubElement(user_style_el, "sld:Name")
+    style_name_el.text = sld_name
+    ET.SubElement(user_style_el, "sld:Title")
+    featuretype_style_el = ET.SubElement(user_style_el, "sld:FeatureTypeStyle")
+    ET.SubElement(featuretype_style_el, "sld:Name")
+    rule_el = ET.SubElement(featuretype_style_el, "sld:Rule")
+    raster_symbolizer_el = ET.SubElement(rule_el, "sld:RasterSymbolizer")
+    geometry_el = ET.SubElement(raster_symbolizer_el, "sld:Geometry")
+    ogc_property_name_el = ET.SubElement(geometry_el, "ogc:PropertyName")
+    ogc_property_name_el.text = "grid"
+    qml_el = minidom.parseString(raw_qml)
+    qml_renderer_el = qml_el.getElementsByTagName("rasterrenderer")[0]
+    raster_type = str(qml_renderer_el.attributes["type"].value)
+    if raster_type == "multibandcolor":
+        raster_symbolizer_el.append(_get_multi_band_channel_selection(qml_el))
+    elif "gradient" in qml_renderer_el.attributes.keys():
+        raster_symbolizer_el.append(_get_gradient_color_map(qml_el))
+    else:  # single band raster
+        raster_symbolizer_el.append(_get_singleband_raster_color_map(qml_el))
+    opacity_el = ET.SubElement(raster_symbolizer_el, "sld:Opacity")
+    opacity_el.text = str(qml_renderer_el.attributes["opacity"].value)
+    return ET.tostring(root_el).decode("utf-8")
+
+
+def _get_multi_band_channel_selection(qml: ET.Element) -> ET.Element:
+    qml_renderer_el = qml.getElementsByTagName("rasterrenderer")[0]
+    red_band = str(qml_renderer_el.attributes["redBand"].value)
+    green_band = str(qml_renderer_el.attributes["greenBand"].value)
+    blue_band = str(qml_renderer_el.attributes["blueBand"].value)
+    channel_selection_el = ET.Element("sld:ChannelSelection")
+    red_channel_el = ET.SubElement(channel_selection_el, "sld:RedChannel")
+    red_source_channel_el = ET.SubElement(red_channel_el, "sld:SourceChannelName")
+    red_source_channel_el.text = red_band
+    green_channel_el = ET.SubElement(channel_selection_el, "sld:GreenChannel")
+    green_source_channel_el = ET.SubElement(green_channel_el, "sld:SourceChannelName")
+    green_source_channel_el.text = green_band
+    blue_channel_el = ET.SubElement(channel_selection_el, "sld:BlueChannel")
+    blue_source_channel_el = ET.SubElement(blue_channel_el, "sld:SourceChannelName")
+    blue_source_channel_el.text = blue_band
+    return channel_selection_el
+
+
+def _get_gradient_color_map(qml: ET.Element) -> ET.Element:
+    min_value = qml.getElementsByTagName("minValue")[0].firstChild.nodeValue
+    max_value = qml.getElementsByTagName("maxValue")[0].firstChild.nodeValue
+    black = "#000000"
+    white = "#FFFFFF"
+    opacity = "1.0"
+    qml_renderer_el = qml.getElementsByTagName("rasterrenderer")[0]
+    if qml_renderer_el.attributes["gradient"].value == "WhiteToBlack":
+        min_color, max_color = (white, black)
+    else:
+        min_color, max_color = (black, white)
+    color_map_el = ET.Element("sld:ColorMap")
+    min_color_map_entry_el = ET.SubElement(color_map_el, "sld:ColorMapEntry")
+    min_color_map_entry_el.attrib["color"] = min_color
+    min_color_map_entry_el.attrib["opacity"] = opacity
+    min_color_map_entry_el.attrib["quantity"] = min_value
+    max_color_map_entry_el = ET.SubElement(color_map_el, "sld:ColorMapEntry")
+    max_color_map_entry_el.attrib["color"] = max_color
+    max_color_map_entry_el.attrib["opacity"] = opacity
+    max_color_map_entry_el.attrib["quantity"] = max_value
+    return color_map_el
+
+
+def _get_singleband_raster_color_map(qml: ET.Element) -> ET.Element:
+    color_map_el = ET.Element("sld:ColorMap")
+    qml_shader_el = qml.getElementsByTagName("colorrampshader")[0]
+    color_type = str(qml_shader_el.attributes["colorRampType"].value)
+    if color_type == "DISCRETE":
+        color_map_el.attrib["type"] = "intervals"
+    for element in qml.getElementsByTagName("item"):
+        color_map_entry_el = ET.SubElement(color_map_el, "sld:ColorMapEntry")
+        color_map_entry_el.attrib["color"] = element.attributes["color"].value
+        color_map_entry_el.attrib["quantity"] = element.attributes["value"].value
+        color_map_entry_el.attrib["label"] = element.attributes["label"].value
+        color_map_entry_el.attrib["opacity"] = "1.0"
+    return color_map_el