gsdview.imgutils

Tools for geo-spatial images handling and visualization.

Functions

histogram_equalized_lut(hist[, dtype, fill])	Compute a histogram equalized LUT.
linear_lut([vmin, vmax, dtype, fill, omin, omax])	Compute a linear LUT.
log_lut([dtype])
root([dtype])
square([dtype])

Classes

BaseStretcher([vmin, vmax, dtype])	Base class for stretcher objects.
LUTStretcher([offset, vmin, vmax, dtype, fill])	Stretch using LUT.
LinearStretcher([scale, offset, vmin, vmax, ...])	Linear stretch.
LogarithmicStretcher([scale, offset, base, ...])	Linear stretch.

class gsdview.imgutils.BaseStretcher(vmin=0, vmax=255, dtype='uint8')

Bases: object

Base class for stretcher objects.

The base implementation of the __call__ method just performs clipping and type conversion (both are optional).

Note

outout extrema (min and max) have to be compatible with the data type (dtype) set.

Example:

data = np.arange(.10, 300.)
stretch = BaseStretch(0, 255, 'uint8')
data = stretch(data)

dtype = None

data type for output data

max = None

the maximum value for output data

min = None

the minimum value for output data

stretchtype = 'clip'

class gsdview.imgutils.LUTStretcher(offset=0, vmin=0, vmax=255, dtype='uint8', fill=True)

Bases: gsdview.imgutils.BaseStretcher

Stretch using LUT.

Perform an arbitrary scaling on unsigned data using a look-up table (LUT).

An optional offset is applied before LUT application.

range

set_range(imin, imax, fill=None)

stretchtype = 'lut'

class gsdview.imgutils.LinearStretcher(scale=1.0, offset=0, vmin=0, vmax=255, dtype='uint8')

Bases: gsdview.imgutils.BaseStretcher

Linear stretch.

Perform linear scaling (including offest application) and clipping.

Note

offset is applyed before scaling:

range

set_range(imin, imax)

stretchtype = 'linear'

class gsdview.imgutils.LogarithmicStretcher(scale=10, offset=0, base=10, vmin=0, vmax=255, dtype='uint8')

Bases: gsdview.imgutils.BaseStretcher

Linear stretch.

Perform logarithmic stretching and clipping:

Note

both base and scale default to 10 while the default value for offset is 0 so the strecher returns values expressed in dB:

stretchtype = 'logarithmic'

gsdview.imgutils.histogram_equalized_lut(hist, dtype='uint8', fill=False)

Compute a histogram equalized LUT.

Parameters:

• hist (ndarray) – histogram to be equalized
• dtype (np.dtype (uint8 or uint16)) – numpy data type of the output LUT (default uint8)
• fill (bool) – if False (default) the returned LUT has . Otherwise the LUT length has a lenght of 2**nbits with nbits bein 8 or 16 depending on dtype and LUT indices greater than the last histogram max value are filled with the maximum value itself.

Returns:

the llok up table (LUT)

gsdview.imgutils.linear_lut(vmin=0, vmax=None, dtype='uint8', fill=False, omin=0, omax=None)

Compute a linear LUT.

The returned LUT maps the imput domain (vmin, vmax) onto the output one (0, vout) using a linear low. The value of vout depends on dtype: 2**8-1 if dtype=’uint8’, 2**16-1 dtype=’uint16’

The fill parameter can be used to controll the length of returned LUT (see below).

Parameters:

• vmin (int or float) – minimum value (positive or null). Default 0
• vmax (int or float) – maximum value (positive) Default 2**nbits depending on dtype
• dtype (np.dtype (uint8 or uint16)) – numpy data type of the output LUT (default uint8)
• fill (bool or int) –

  the length of the returned lut is:

  • vmax + 1 if bool(fill) == False
  • max(vmax + 1, 2**nbits) if fill == True
  • max(vmax + 1, fill) id fille is an number

• omin – @TBW
• omax – @TBW

Returns:

the look up tabe (LUT)

gsdview.imgutils.log_lut(dtype='uint8')

gsdview.imgutils.root(dtype='uint8')

gsdview.imgutils.square(dtype='uint8')