fixation-target 1.0.1

Generate customizable fixation targets for vision science experiments

Visual Fixation Target

A Python package to generate customizable fixation targets for vision science experiments.

Description

This package generates fixation target configurations as described by Thaler et al. (2013). It supports different target types:

• A: Center dot only
• B: Outer circle only
• C: Cross only
• AB, AC, BC: Combinations of two components
• ABC: All components (center dot + outer circle + cross)

All dimensions are specified in visual angles (degrees) and automatically converted to pixels based on your screen parameters.

Target Type Examples

A (Center dot)	B (Outer circle)	C (Cross)	AB (Center + Outer)
AC (Center + Cross)	BC (Outer + Cross)	ABC (All components)

Installation

From PyPI

pip install fixation-target

From source

git clone https://github.com/mh-salari/fixation-target.git
cd fixation-target
pip install -e .

Usage

Command-line Interface

Using a JSON configuration file

Create a JSON config file with your parameters:

{
  "screen_width_mm": 476.64,
  "screen_height_mm": 268.11,
  "screen_width_px": 1920,
  "screen_height_px": 1080,
  "viewing_distance_mm": 930,
  "target_type": "ABC",
  "center_diameter_in_degrees": 0.1,
  "outer_diameter_in_degrees": 0.6,
  "cross_width_in_degrees": 0.15,
  "center_color": [0, 0, 0, 255],
  "outer_color": [0, 0, 0, 255],
  "cross_color": [255, 255, 255, 255],
  "background_diameter_in_degrees": 1.0,
  "background_color": [128, 128, 128, 255]
}

Load and use it:

fixation-target --json config.json --output output/

Using command-line arguments

fixation-target \
  --output output/ \
  --target-type ABC \
  --screen-width-mm 476.64 \
  --screen-height-mm 268.11 \
  --screen-width-px 1920 \
  --screen-height-px 1080 \
  --viewing-distance-mm 930 \
  --center-diameter 0.1 \
  --outer-diameter 0.6 \
  --cross-width 0.15 \

Python API

from pathlib import Path
from fixation_target import fixation_target

# Generate an ABC target
fixation_target(
    screen_width_mm=476.64,
    screen_height_mm=268.11,
    screen_width_px=1920,
    screen_height_px=1080,
    viewing_distance_mm=930,
    save_path=Path("output"),
    target_type="ABC",
    center_diameter_in_degrees=0.1,
    outer_diameter_in_degrees=0.6,
    cross_width_in_degrees=0.15,
    center_color=(0, 0, 0, 255),      # black
    outer_color=(0, 0, 0, 255),       # black
    cross_color=(255, 255, 255, 255), # white
    background_diameter_in_degrees=1.0,
    background_color=(128, 128, 128, 255),  # gray
    show=True
)

Target Types

• A: Center dot only - useful for minimal fixation point
• B: Outer circle only - provides a reference boundary
• C: Cross only - traditional fixation cross
• AB: Center dot + outer circle
• AC: Center dot + cross
• BC: Outer circle + cross
• ABC: All components (recommended for stable fixation)

Parameters

Required Screen Parameters

• screen_width_mm: Physical width of your screen in millimeters
• screen_height_mm: Physical height of your screen in millimeters
• screen_width_px: Screen resolution width in pixels
• screen_height_px: Screen resolution height in pixels
• viewing_distance_mm: Distance from viewer to screen in millimeters

Target Parameters

• target_type: One of "A", "B", "C", "AB", "AC", "BC", "ABC" (default: "ABC")
• center_diameter_in_degrees: Diameter of center dot in visual degrees (default: 0.1)
• outer_diameter_in_degrees: Diameter of outer circle in visual degrees (default: 0.6)
• cross_width_in_degrees: Width of cross lines in visual degrees (default: 0.15)
• center_color: RGBA color tuple for center dot (default: black)
• outer_color: RGBA color tuple for outer circle (default: black)
• cross_color: RGBA color tuple for cross (default: white)
• background_diameter_in_degrees: Optional background circle diameter
• background_color: Optional background circle color (RGBA tuple)
• show: Whether to display the generated image (default: True)

Reference

Thaler, L., Schütz, A.C., Goodale, M.A., & Gegenfurtner, K.R. (2013). What is the best fixation target? The effect of target shape on stability of fixational eye movements. Vision Research, 76, 31-42. https://doi.org/10.1016/j.visres.2012.10.012

Author

Mohammadhossein Salari Email: [e-mail]