expyriment.stimuli.Canvas

class expyriment.stimuli.Canvas(size, position=None, colour=None)

A class implementing a canvas stimulus.

__init__(size, position=None, colour=None)

Create a canvas.

Parameters:

size(int, int)

size of the canvas (int,int)

position(int, int), optional

position of the stimulus

colour(int,int,int), optional

colour of the canvas stimulus

property absolute_position

Getter for absolute_position.

Notes

The absolute position differs for instance from the (relative) position, if the stimulus is plotted ontop of another stimulus, which has not the position (0,0).

add_noise(grain_size, percentage, colour)

Add visual noise on top of the stimulus.

This function might take very long for large stimuli.

Parameters:

grain_sizeint

size of the grains for the noise

percentageint

percentage of covered area

colour(int, int, int)

colour (RGB) of the noise

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

blur(level)

Blur the stimulus.

This blurs the stimulus, by scaling it down and up by the factor of ‘level’.

Parameters:

levelint

level of bluring

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

clear_surface()

Clear the stimulus surface.

Surfaces are automatically created after any surface operation (presenting, plotting, rotating, scaling, flipping etc.) and preloading. If the stimulus was preloaded, this method unloads the stimulus. This method is functionally equivalent with unload(keep_surface=False).

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

property colour

Getter for colour.

compress()

“Compress the stimulus.

This will create a temporary file on the disk where the surface of the stimululs is written to. The surface will now be read from the disk to free memory. Compressed stimuli cannot do surface operations! Preloading comressed stimuli is possible and highly recommended. Depending on the size of the stimulus, this method may take some time to compute!

Returns:

timeint

the time it took to execute this method

copy()

Deep copy of the visual stimulus.

Returns:

copydeep copy of self

Notes

Depending on the size of the stimulus, this method may take some time to compute!

decompress()

Decompress the stimulus.

This will decompress the stimulus. The surface will now be read from memory again. Depending on the size of the stimulus, this method may take some time to compute!

Returns:

timeint

the time it took to execute this method

distance(other)

Surface center distance.

This method computes the distance between the surface center of this and another visual stimulus.

Parameters:

otherstimulus

the other visual stimulus

Returns:

distfloat

distance between surface centers

flip(booleans)

Flip the stimulus.

This is a surface operation. After this, a surface will be present!

Parameters:

booleans(bool, bool)

booleans to flip or not

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

get_pixel_array()

Return a 2D array referencing the surface pixel data.

Returns:

pixel_array: Pygame.PixelArray

a 2D array referencing the surface pixel data

Notes

see also set_surface

get_surface_array(replace_transparent_with_colour=None)

Get a 3D array containing the surface pixel data.

Returns:

surface_arraynumpy.ndarray

a 3D array containing the surface pixel data using RGBA coding.

get_surface_copy()

Returns a copy of the Pygame surface of the stimulus

Returns:

surface: Pygame.surface

Notes

see also set_surface

property has_surface

Getter for has_surface.

property id

Getter for id.

inside_stimulus(stimulus, mode='visible')

Check if stimulus is inside another stimulus.

Parameters:

stimulusexpyriment stimulus

the other stimulus

modemode (str), optional

“visible”: based on non-transparent pixels or “surface”: based on pixels in pygame surface (default = visible”)

Returns:

outbool

Notes

Depending on the size of the stimulus, this method may take some time to compute!

property is_compressed

Getter for is_compressed.

property is_preloaded

Getter for is_preloaded.

property logging

Getter for logging.

move(offset)

Moves the stimulus in 2D space.

When using OpenGL, this can take longer then 1ms!

Parameters:

offsettuple (x,y)

translation along x and y axis

Returns:

timeint

the time it took to execute this method

Notes

see also reposition

overlapping_with_position(position, mode='visible', use_absolute_position=True)

Check if stimulus is overlapping with a certain position.

Parameters:

position(int, int)

position to check for overlapping

modemode (str), optional

“visible”: based on non-transparent pixels or “rectangle”: based on pixels in pygame surface (default = visible”)

use_absolute_positionbool, optional

use absolute_position of stimulus (default) instead of position

Returns:

overlappingbool

Notes

Depending on the size of the stimulus, this method may take some time to compute!

CAUTION: Please note that if a stimulus is plotted on another smaller stimulus, such that it is not fully visible on screen, this method will still check overlapping of the full stimulus! Due to a current bug in Pygame, we can right now not change this.

overlapping_with_stimulus(stimulus, mode='visible', use_absolute_position=True)

Check if stimulus is overlapping with another stimulus.

Parameters:

stimulusexpyriment stimulus

the other stimulus

modemode (str), optional

“visible”: based on non-transparent pixels or “surface”: based on pixels in pygame surface (default = visible”)

use_absolute_positionbool, optional

use absolute_position of stimuli (default) instead of position

Returns:

overlappingbool

are stimuli overlapping or not

overlap(int, int)

the overlap (x, y) in pixels. If mode is ‘surface’, the argument will always be None.

Notes

Depending on the size of the stimulus, this method may take some time to compute!

CAUTION: Please note that if a stimulus is plotted on another smaller stimulus, such that it is not fully visible on screen, this method will still check overlapping of the full stimulus! Due to a current bug in Pygame, we can right now not change this.

picture()

Return the stimulus as Picture stimulus.

This will create a temporary file on the hard disk where the image is saved to.

Notes

Depending on the size of the stimulus, this method may take some time to compute!

plot(stimulus)

Plot the stimulus on the surface of another stimulus.

Use this to plot more than one stimulus and to present them at the same time afterwards by presenting the stimulus on which they were plotted on.

Parameters:

stimulusexpyriment stimulus

stimulus to whose surface should be plotted

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

property polar_position

Getter for the position in polar coordinates (radial, angle[degrees])

property position

Getter for position.

preload(inhibit_ogl_compress=False)

Preload the stimulus to memory.

This will prepare the stimulus for a fast presentation. In OpenGL mode this method creates an OpenGL texture based on the surface of the stimulus. When OpenGL is switched off, this method will create a surface if it doesn’t exists yet. If stimuli are not preloaded manually, this will happen automatically during presentation. However, stimulus presentation will take some time then!

Always preload your stimuli when a timing accurate presentation is needed!

Parameters:

inhibit_ogl_compressbool, optional

inhibits OpenGL stimuli to be automatically compressed (default=False)

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

present(clear=True, update=True, log_event_tag=None)

Present the stimulus on the screen.

This clears and updates the screen automatically. When not preloaded, depending on the size of the stimulus, this method can take some time to compute!

Parameters:

clearbool, optional

if True the screen will be cleared automatically (default = True)

updatebool, optional

if False the screen will be not be updated automatically (default = True)

log_event_tagnumeral or string, optional

if log_event_tag is defined and if logging is switched on for this stimulus (default), a summary of the inter-event-intervalls are appended at the end of the event file

Returns:

timeint

the time it took to execute this method

reposition(new_position)

Move stimulus to a new position.

When using OpenGL, this can take longer then 1ms!

Parameters:

new_positiontuple (x,y)

translation along x and y axis

Returns:

timeint

the time it took to execute this method

Notes

see also move

rotate(degree, filter=True)

Rotate the stimulus.

This is a surface operation. After this, a surface will be present! Rotating goes along with a quality loss. Thus, rotating an already rotated stimulus is not a good idea.

Parameters:

degreeint

degree to rotate counterclockwise

filterbool, optional

filter the surface content for better quality (default = True)

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

save(filename)

Save the stimulus as image.

Parameters:

filenamestr

name of the file to write (possible extensions are BMP, TGA, PNG, or JPEG with TGA being the default)

Notes

Depending on the size of the stimulus, this method may take some time to compute!

scale(factors)

Scale the stimulus.

This is a surface operation. After this, a surface will be present! Negative scaling values will flip the stimulus. Scaling goes along with a quality loss. Thus, scaling an already scaled stimulus is not a good idea.

Parameters:

factors(int, int) or (float, float)

tuple representing the x and y factors to scale or a single number. In the case of a single number x and y scaling will be the identical (i.e., proportional scaling)

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

scale_to_fullscreen(keep_aspect_ratio=True)

Scale the stimulus to fullscreen.

This is a surface operation. After this, a surface will be present! Scaling goes along with a quality loss. Thus, scaling an already scaled stimulus is not a good idea.

Parameters:

keep_aspect_ratioboolean, optional

if this boolean is False, stimulus will be stretched so that it fills out the whole screen (default = False)

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

scramble(grain_size)

Scramble the stimulus.

Attention: If the surface size is not a multiple of the grain size, you may loose some pixels on the edge.

Parameters:

grain_sizeint or (int, int)

size of a grain (use tuple of integers for different width & height)

Returns:

timeint

the time it took to execute this method

Notes

Depending on the size of the stimulus, this method may take some time to compute!

set_logging(onoff)

Set logging of this object on or off

Parameters:

onoffbool

set logging on (True) or off (False)

See also

expyriment.design.Experiment.set_log_level

set_surface(surface)

Set the surface of the stimulus

This method overwrites the surface of the stimulus. It can also handle surfaces in form of pygame.PixelArray or Numpy 3D array (RGB or RGBA) representations.

Parameters:

surface: pygame.Surface or pygame.PixelArray or numpy.ndarray

a representation of the new surface

Returns:

succeeded: boolean

setting surface was successful or not

Notes

CAUTION: This is an expert’s method. The method can be used together with get_surface() & get_pixel_array() to apply low-level Pygame operations on stimuli. However, users should be aware of what they are doing, because the incorrect usage of this methods might affect the stability of the experiment.

property size

Getter for size.

property surface_size

Getter for surface_size.

unload(keep_surface=False)

Unload the stimulus from memory.

This will unload preloaded stimuli. In OpenGL mode, this method will remove the reference to the OpenGL texture and the surface (when ‘keep_surface’ is False). When OpenGL is switched off, the reference to the surface will be removed (when ‘keep_surface’ is False).

Parameters:

keep_surfacebool, optional

keep the surface after unload (default=False)

Returns:

timeint

the time it took to execute this method

See also

clear_surface

Notes

Depending on the size of the stimulus, this method may take some time to compute!