Table of Contents
• OWS Configuration - Colourmap Styles – Colour-Map Styles
* value_map · Value Rules
· Color, Alpha and Mask · Title and Abstract · Rules
· Bitflag Rules (flags) · Simple Rules · And Rules · Or Rules
· Enumeration Rules (values) * Legend
· Values passed to MatPlotLib
· Image Size
· MatPlotLib rc params
4.10.1 Colour-Map Styles
Colour-map Styles arestyleswhere each pixel is mapped to one particular colour from a fixed pallet by applying a logical decision tree to the flag data for that pixel.
Colour-map styles support theelements common to all styles.
Colour-map styles also have value_map entry that describes how the colour of individual pixels is determined. Colour-map styles supportautomatic legend generation.
value_map
The value_map is dictionary mapping bands to a list of value rules. The key is a name or alias of a bitmap band. Multiple bands are possible but it is strongly recommended to use only a single band, because the order in which rules are processed cannot be guaranteed in a multiple band scenario.
A value rule set is a list of value rules. The rules are applied in order. Each pixel will take the the colour specified by the first value rule in the set that the pixel satisifies. Any pixel that does not match any rules will be fully transparent. E.g.:
"value_map": { "band_1": [
band1_rule1,
# A pixel that matches both band1_rule1 AND band2_rule2 will be # coloured according to band1_rule1, as it appears first in the # list.
band1_rule2, band1_rule3,
# A pixel that doesn't match any rules will remain transparent. ],
# Multiple bands are strongly discouraged as you have # no control over whether the band1 rules or band2 rules # will applied first. Multiple bands can only be safely used # where the structure of the data means that no single pixel can # match a rule for both bands.
# # "band_2": [ # band2_rule1, # band2_rule2, # ], }, Value Rules
Color, Alpha and Mask
Each rule must have a color entry that specifies the appearance of pixels that match the rule. The color entry is in html RGB hex format.
The alpha and mask entries are optional and allow transparency. alpha should be a floating point number between 0.0 (fully transparent) and 1.0 (fully opaque) and defaults to 1.0 (i.e. fully transparent). The mask entry is boolean (default False). Setting mask to true is the same equivalent to setting alpha to 0.0. (A third option would be to use the standard stylepq_masks. Bit-flag Masks (pq_masks)
syntax.)
to achieve the same effect
coloris still required when mask is True, but is not used in this case. E.g.:
# fully opaque red "color": "#FF0000",
# 50% transparent green "color": "#00FF00", "alpha": 0.5,
# Fully transparent (note that color is required but not used) "color": "#999999",
"mask": True
Title and Abstract
Each rule must have a title and abstract which is used for automatic legend generation. The text for the corresponding legend entry will be “<title> - <abstract>”.
E.g.:
"value_map": {
"bitflag_band": [ {
# legend entry text will be "Open Forest - (50% - 80% cover)" "title": "Open Forest",
"abstract": "(50% - 80% cover)", ... }, ] } Rules
Each Value Rule must also specify the rule to evaluate when it applies.
This can be done either by treating the band as a bit-flag ( with the‘flags<#bitflag-rules-flags>‘_entry) or as an enumeration ( with the‘values<#enumeration-rules-values>‘_entry).
Bitflag Rules (flags)
For bitflag bands, the actual logic of the Value Rule is contained in the “flags” entry.
The flags entry is a dictionary with one of three possible formats. Note that formats cannot be combined. In particular andand or logic cannot be combined in a single rule.
Refer to the OpenDataCube metadata for the underlying product for the valid bitflag names.
Simple Rules
A simple rule allows matching a single bitflag value. The flags dictionary contains a single entry, the key is a valid bitflag for the band, and the value is boolean.
E.g.: "value_map": { "bitflag_band": [ ... { ... "flags": {
# matches all pixels that have not already matched a previous rule # and have the "open_forest" bit flag set to True.
"open_forest": True, } }, ... ] And Rules
And Rules allow a pixel match if all the specified comparisons match. The flags entry contains an “and” dictionary that in turn contains the individual comparisons.
E.g.: "value_map": { "bitflag_band": [ ... { ... "flags": { "and": {
# matches all pixels that have not already matched a previous rule # and have the "open_forest" bit flag set to True AND the
˓→"underwater"
# bit flag set to False. "open_forest": True, "underwater": False, } } }, ... ] Or Rules
Or Rules allow a pixel match if any of the specified comparisons match. The flags entry contains an “or” dictionary that in turn contains the individual comparisons.
"value_map": { "bitflag_band": [ ... { ... "flags": { "or": {
# matches all pixels that have not already matched a previous rule # and have either the "open_forest" or the "closed_forest" bit ˓→flag set # to True. "open_forest": True, "closed_forest": True, } } }, ... ]
Enumeration Rules (values)
For bitflag bands, the actual logic of the Value Rule is contained in the “values” entry. The “values” entry is a list of integers. Pixels whose exact value is in this list satisfy the rule. E.g. "value_map": { "enum_band": [ ... { ...
# Matches pixels whose value is exactly either 2, 3, 7 or 15. "values": [2, 3, 7, 15],
}, ... ]
Legend
Colour map styles support automatic legend configuration.
Automatic legend generation can be deactivated using the show_legend and url legend elementscommon to all styles. (show_legend is True by default for colour-map styles.)
A patch and label is added to the legend for each value rule in the configuration. Seetitle and abstractfor customising the label of each rule.
Values passed to MatPlotLib
Colour ramp auto-legends are created using the MatPlotLib library. The following values are passed directly to the MatPlotLib library. Please refer to theMatPlotLib documentationfor further information.
Image Size
The width and height values are passed to matplotlib to specify the size of the generated image.
The image size defaults to 3 inches wide by 1.25 inches tall. The default dpi for MatPlotLib is 100, so this corresponds to 300x125 pixels unless you have over-ridden the default dpi.
E.g.: "legend": { "width": 4.5, "height": 2.1 } MatPlotLib rc params
Other MatPlotLib customisations (as they would appear in a .matplotlibrc file) can be specified with the optional rcParamselement, defaulting to {}, meaning the MatPlotLib defaults for all options.
For a full list of possible options refer tothe MatPlotLib documentation
E.g.: "legend": { "rcParams": { "lines.linewidth": 2, "font.weight": "bold", }, }