Image Component¶

The Image stimulus allows an image to be presented, which can be a bitmap image from a variety of standard file formats, with an optional transparency mask that can effectively control the shape of the image. The mask can also be derived from an image file, or mathematical form such as a Gaussian.

It is a really good idea to get your image in roughly the size (in pixels) that it will appear on screen to save memory. If you leave the resolution at 12 megapixel camera, as taken from your camera, but then present it on a standard screen at 1680x1050 (=1.6 megapixels) then |PsychoPy| and your graphics card have to do an awful lot of unnecessary work. There is a performance advantage (in terms of milliseconds) to using images which are square and powers of two (32, 64, 128, etc.), but this is slight and would not be noticed in the majority of experiments.

Images can have their position, orientation, size and other settings manipulated on a frame-by-frame basis.

Categories:: Stimuli
Works in:: PsychoPy, PsychoJS

Parameters¶

Basic¶

The required attributes of the stimulus, controlling its basic function and behaviour

Name: Everything in a PsychoPy^® experiment needs a unique name. The name should contain only letters, numbers and underscores (no punctuation marks or spaces).

Start: When the Image Component should start, see Defining the onset/duration of components.

Expected start (s): If you are using frames to control timing of your stimuli, you can add an expected start time to display the component timeline in the routine.

Start type

How do you want to define your start point?

Options:

time (s)
frame N
condition

Stop: When the Image Component should stop, see Defining the onset/duration of components.

Expected duration (s): If you are using frames to control timing of your stimuli, you can add an expected duration to display the component timeline in the routine.

Stop type

How do you want to define your end point?

Options:

duration (s)
duration (frames)
time (s)
frame N
condition

Image: A filename or a standard name (sin, sqr). Filenames can be relative or absolute paths and can refer to most image formats (e.g. tif, jpg, bmp, png, etc.). If this is set to none, the patch will be a flat colour.

Layout¶

How should the stimulus be laid out on screen? Padding, margins, size, position, etc.

Size [w,h]: Size of this stimulus (either a single value or x,y pair, e.g. 2.5, [1,2] ). If the mask is a Gaussian then the size refers to width at 3 standard deviations on either side of the mean (i.e. sd=size/6) Set this to be blank to get the image in its native size.

Position [x,y]: Position of this stimulus (e.g. [1,2] )

Spatial units

Spatial units for this stimulus (e.g. for its position and size), see Units for the window and stimuli for more info.

Options:

from exp settings
deg
cm
pix
norm
height
degFlatPos
degFlat

Anchor

Which point in this stimulus should be anchored to the point specified by Position [x,y]?

Options:

center
top-center
bottom-center
center-left
center-right
top-left
top-right
bottom-left
bottom-right

Orientation

Orientation of this stimulus (in deg)

Options:

-360
360

Flip vertically: Should the image be flipped vertically (top to bottom)?

Flip horizontally: Should the image be flipped horizontally (left to right)?

Draggable?: Should this stimulus be moveble by clicking and dragging?

Appearance¶

How should the stimulus look? Colors, borders, styles, etc.

Foreground color: Foreground color of this stimulus (e.g. $[1,1,0], red )

Color space

In what format (color space) have you specified the colors? See Color spaces for more info.

Options:

Opacity: Vary the transparency, from 0.0 (invisible) to 1.0 (opaque)

Contrast: Contrast of the stimulus (1.0=unchanged contrast, 0.5=decrease contrast, 0.0=uniform/no contrast, -0.5=slightly inverted, -1.0=totally inverted)

Texture¶

Mask: A filename, a standard name (gauss, circle, raisedCos) or a numpy array of dimensions NxNx1. The mask can define the shape (e.g. circle will make the patch circular) or something which overlays the patch e.g. noise.

Texture resolution: This is only needed if you use a synthetic texture (e.g. sinusoidal grating) as the image.

Interpolate

If linear is selected then linear interpolation will be applied when the image is rescaled to the appropriate size for the screen. Nearest will use a nearest-neighbour rule.

Options:

linear
nearest

Data¶

What information about this Component should be saved?

Save onset/offset times: Store the onset/offset times in the data file (as well as in the log file).

Sync timing with screen refresh: Synchronize times with screen refresh (good for visual stimuli and responses based on them)

Testing¶

Tools for testing, debugging and checking the performance of this Component.

Disable Component: Disable this Component

Validate with…: Name of the Validator Routine to use to check the timing of this stimulus. Options are generated live, so will vary according to your setup.