Image Stimulus¶

Description¶

An image stimulus loaded from any standard-format image file.

Note: To preserve the image’s aspect ratio on screen, x_size and y_size must be equal. When drawn, the larger dimension spans the full specified size, while the smaller dimension is scaled to maintain the aspect ratio.

Signature¶

stimulus/image_file

Required Parameters¶

path¶

Examples:: images/image1.png

/path/to/image.png

Filesystem path to the image file

Optional Parameters¶

announce_load¶

Default:: YES

If YES, messages will be posted to the console and event stream when the image is loaded or unloaded.

alpha_multiplier¶

Default:: 1.0

By default, the alpha multiplier controls the transparency of the stimulus. 1.0 is fully opaque, while 0.0 is fully tranparent.

Changes to the parameters source_blend_factor and dest_blend_factor can alter how (or if) the alpha multiplier is used.

Note: If the image contains an alpha channel, the embedded alpha value for each pixel is multiplied by the value of this parameter.

source_blend_factor¶

Options:: zero

one

source_color

one_minus_source_color

dest_color

one_minus_dest_color

source_alpha

one_minus_source_alpha

dest_alpha

one_minus_dest_alpha
Default:: source_alpha

Source blending factor.

The parameters source_blend_factor, dest_blend_factor, source_alpha_blend_factor, and dest_alpha_blend_factor provide detailed control over how the color components and alpha multiplier of each fragment of the stimulus (the “source”) are combined with the color and alpha values already present in the framebuffer (the “destination”), which in turn result from blending the stimulus display background with any stimuli drawn beneath the source stimulus. These parameters correspond directly to the four arguments of the OpenGL function glBlendFuncSeparate. Please refer to that function’s reference page for explanations of the different blend factor options.

Note: Irrespective of the blend factors used, the blend equation is always GL_FUNC_ADD.

dest_blend_factor¶

Default:: one_minus_source_alpha

Destination blending factor. Accepts the same values as source_blend_factor.

source_alpha_blend_factor¶

Source alpha blending factor. Accepts the same values as source_blend_factor.

If omitted, the value of source_blend_factor is used.

dest_alpha_blend_factor¶

Destination alpha blending factor. Accepts the same values as source_blend_factor.

If omitted, the value of dest_blend_factor is used.

x_size¶

Example:: 5.0

Horizontal size (degrees).

If omitted, the value of y_size is used. It is an error to omit both x_size and y_size (unless fullscreen is YES).

y_size¶

Example:: 5.0

Vertical size (degrees).

If omitted, the value of x_size is used. It is an error to omit both x_size and y_size (unless fullscreen is YES).

x_position¶

Default:: 0.0

Horizontal center position (degrees)

y_position¶

Default:: 0.0

Vertical center position (degrees)

rotation¶

Default:: 0.0

Rotation (degrees)

fullscreen¶

Default:: NO

If YES, the stimulus is sized to fill the display. In this mode, x_size, y_size, x_position, y_position, and rotation are ignored.

deferred¶

Options:: no

yes

explicit
Default:: no

Controls when the stimulus is loaded. If no, the stimulus is loaded at experiment load time. If yes, the stimulus is loaded the first time it is queued. If explicit, the stimulus must be loaded explictly with Load Stimulus.

display¶

Name of the display on which the stimulus will be presented. If omitted, the default display (if available) will be used.

Placement¶

Allowed at top level:	Yes
Allowed parent:	Compound Stimulus, Folder, Frame List Stimulus, Layer Stimulus, List Replicator, Movie Stimulus, Range Replicator, Stimulus Group