fileinfo

Utility classes for accessing information from files, ouside of the main RIOS applier structure. Typically these are used to access information required to set up the call to rios.applier.apply(), passing some of the information in via the otherargs parameter.

class rios.fileinfo.ColumnStats(band, columnName, includeImageNull=False, histogramweighted=True)[source]

Summary statistics for a single column of a raster attribute table

Attributes are:
  • count
  • mean
  • stddev
  • min
  • max
  • mode Not yet implemented
  • median Not yet implemented

Unless otherwise requested, the statistics are weighted by the Histogram column, so that they represent spatial statistics, e.g. the mean would correspond to the mean over all pixels, rather than the mean over all rows, and the count is effectively the number of pixels, rather than the number of rows. This can be disabled by setting histogramweighted=False when calling the constructor.

Unless otherwise requested, rows which correspond to the image null value are not included in stats calculation. This can be reversed by setting includeImageNull=True on the constructor, although normally the histogram does not include counts for the null value either, so this only really makes sense when using histogramweighted=False. (N.B. that last point assumes the presence of the GDAL patches for tickets #4750 and #5289. )

class rios.fileinfo.ImageFileStats(filename)[source]

Hold the stats for all layers in an image file. This object can be indexed with the layer index, and each element is an instance of rios.fileinfo.ImageLayerStats.

class rios.fileinfo.ImageInfo(filename, omitPerBand=False)[source]

An object with the bounds and other info for the given image, in GDAL conventions.

Object contains the following fields
  • xMin Map X coord of left edge of left-most pixel
  • xMax Map X coord of right edge of right-most pixel
  • yMin Map Y coord of bottom edge of bottom pixel
  • yMax Map Y coord of top edge of top-most pixel
  • xRes Map coord size of each pixel, in X direction
  • yRes Map coord size of each pixel, in Y direction
  • nrows Number of rows in image
  • ncols Number of columns in image
  • transform Transformation params to map between pixel and map coords, in GDAL form
  • projection WKT string of projection
  • rasterCount Number of rasters in file
  • lnames Names of the layers as a list.
  • layerType “thematic” or “athematic”, if it is set
  • dataType Data type for the first band (as a GDAL integer constant)
  • dataTypeName Data type for the first band (as a human-readable string)
  • nodataval Value used as the no-data indicator (per band)

The omitPerBand argument on the constructor is provided in order to speed up the access of very large VRT stacks. The information which is normally extracted from each band will, in that case, trigger a gdal.Open() for each band, which can be quite slow. So, if none of that information is actually required, then setting omitPerBand=True will omit that information, but will return as quickly as for a normal single file.

getCorners(outWKT=None, outEPSG=None, outPROJ4=None)[source]

Return the coordinates of the image corners, possibly reprojected.

This is the same information as in the xMin, xMax, yMin, yMax fields, but with the option to reproject them into a given output projection. Because the output coordinate system will not in general align with the image coordinate system, there are separate values for all four corners. These are returned as:

(ul_x, ul_y, ur_x, ur_y, lr_x, lr_y, ll_x, ll_y)

The output projection can be given as either a WKT string, an EPSG number, or a PROJ4 string. If none of those is given, then bounds are not reprojected, but will be in the same coordinate system as the image corners.

layerNameFromNumber(layerNumber)[source]

Return the layer name corresponding to the given layer number. Valid layer numbers are as per GDAL conventions, i.e. starting at 1. If the given layer number is not valid for this file info, an exception is raised.

layerNumberFromName(layerName)[source]

Return the layer number corresponding to the given layer name. Valid layer numbers are as per GDAL conventions, i.e. starting at 1. If the given layer name is not found in this file info, then zero is returned.

class rios.fileinfo.ImageLayerStats(bandObj)[source]

Hold the stats for a single image layer. These are as retrieved from the given image file, and are not calculated again. If they are not present in the file, they will be None. Typically this class is not used separately, but only instantiated as a part of the ImageFileStats class.

The object contains the following fields
  • mean Mean value over all non-null pixels
  • min Minimum value over all non-null pixels
  • max Maximum value over all non-null pixels
  • stddev Standard deviation over all non-null pixels
  • median Median value over all non-null pixels
  • mode Mode over all non-null pixels
  • skipfactorx The statistics skip factor in the X direction
  • skipfactory The statistics skip factor in the Y direction

There are many ways to report a histogram. The following attributes report it the way GDAL does. See GDAL doco for precise details.

  • histoCounts Histogram counts (numpy array)
  • histoMin Minimum edge of smallest bin
  • histoMax Maximum edge of largest bin
  • histoNumBins Number of histogram bins
class rios.fileinfo.RatStats(filename, columnlist=None, layernum=1, includeImageNull=False, histogramweighted=True)[source]

Calculate statistics on columns in a Raster Attribute Table

Normal usage is via the RatStats class, e.g.:

columnsOfInterest = ['col1', 'col4']
ratStatsObj = ratstats.RatStats('file.img', columnlist=columnsOfInterest)

print ratStatsObj.col1.mean, ratStatsObj.col4.mean

Contains an attribute for each named column. Each attribute is a ColumnStats object, containing all relevant global stats for that column. See docstring for that class for details.

class rios.fileinfo.VectorFileInfo(filename)[source]

Hold useful general information about a vector file. This object can be indexed with the layer index, and each element is an instance of rios.fileinfo.VectorLayerInfo.

class rios.fileinfo.VectorLayerInfo(ds, i)[source]

Hold useful general information about a single vector layer.

Object contains the following fields
  • featureCount Number of features in the layer
  • xMin Minimum X coordinate
  • xMax Maximum X coordinate
  • yMin Minimum Y coordinate
  • yMax Maximum Y coordinate
  • geomType OGR geometry type code (integer)
  • geomTypeStr Human-readable geometry type name (string)
  • fieldCount Number of fields (i.e. columns) in attribute table
  • fieldNames List of names of attribute table fields
  • fieldTypes List of the type code numbers of each attribute table field
  • fieldTypeNames List of the string names of the field types
  • spatialRef osr.SpatialReference object of layer projection
rios.fileinfo.preventGdal3axisSwap(sr)[source]

Guard the given spatial reference object against axis swapping, when running with GDAL 3. Does nothing if GDAL < 3. Modifies the object in place.