pulse2percept.stimuli.psychophysics.landolt_c

pulse2percept.stimuli.psychophysics.landolt_c(gap=1, position=(0, 0), orientation=0, fov=10, polarity='dark', shape=(512, 512))[source]

Landolt C optotype

Rasterize a Landolt C and place it in a Scene.

The C uses standard proportions: the stroke and gap are equal, with inner and outer diameters of 3 * gap and 5 * gap. The analytic glyph is supersampled and area-averaged onto the requested raster; gap must span at least three output pixels.

Added in version 0.11.0.

Parameters:

  • gap (float or Quantity, optional) – Angular width of the critical opening, in degrees of visual angle (e.g. 0.5 * dva).

  • position ((x, y), optional) – Center of the optotype in visual-field coordinates, in dva. y grows upwards.

  • orientation (float or Quantity, optional) – Direction the opening points, in degrees counterclockwise from the positive x axis (e.g. 90 * deg): 0 right, 90 up, 180 left, 270 down. Any finite angle is accepted.

  • fov (float or (width, height), optional) – How much of the visual field the scene covers, in dva. A scalar is the horizontal extent, and the vertical one follows from shape.

  • polarity ({'dark', 'light'}, optional) – 'dark' draws a black C on white, 'light' a white C on black.

  • shape ((rows, cols), optional) – Size of the rasterized frame, in pixels.

Returns:

scene

Return type:

Scene

Examples

A 0.5-degree gap pointing up, five degrees to the right of fixation:

>>> from pulse2percept.stimuli import psychophysics
>>> from pulse2percept.units import deg, dva
>>> scene = psychophysics.landolt_c(gap=0.5 * dva,
...                                 position=(5, 0) * dva,
...                                 orientation=90 * deg, fov=15 * dva)
>>> scene.fov
(15.0, 15.0)