added circular bullseye (function+demo)

demo/circular.ipynb

@@ -155,6 +155,51 @@
     "display(ui, out)\n"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# circular_bullseye\n",
+    "\n",
+    "This function produces the same stimulus as `circular_white()` but always with a single central target."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from stimuli.illusions.circular import circular_bullseye"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Parameterization"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "params = {\n",
+    "    \"visual_size\": (10., 10.),\n",
+    "    \"ppd\": 40.0,\n",
+    "    \"frequency\": 1.,\n",
+    "    \"intensity_discs\": (0., 1.),\n",
+    "    \"intensity_background\": 0.5,\n",
+    "    \"intensity_target\": 0.5,\n",
+    "}\n",
+    "\n",
+    "stim = circular_bullseye(**params)\n",
+    "plot_stim(stim)\n",
+    "plt.show()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},

stimuli/illusions/circular.py

@@ -5,7 +5,7 @@
 
 def circular_white(
     visual_size=(10, 10),
-    ppd=18,
+    ppd=30,
     frequency=1,
     intensity_discs=(0., 1.),
     intensity_background=0.2,
@@ -107,6 +107,52 @@ def circular_white(
     return {"img": img, "mask": mask.astype(int),  **params}
 
 
+def circular_bullseye(
+    visual_size=(10, 10),
+    ppd=30,
+    frequency=1,
+    intensity_discs=(0., 1.),
+    intensity_background=0.2,
+    intensity_target=0.5,
+    ssf=1,
+):
+    """
+    Circular Bullsseye stimulus
+
+    Parameters
+    ----------
+    visual_size : (float, float)
+        The shape of the stimulus in degrees of visual angle. (y,x)
+    ppd : int
+        pixels per degree (visual angle)
+    frequency : float
+        the spatial frequency of the circular grating in cycles per degree
+    intensity_discs : (float, float)
+        intensity values of discs
+    intensity_background : float
+        intensity value of background
+    intensity_target : float
+        intensity value of target discs
+    ssf : int (optional)
+          the supersampling-factor used for anti-aliasing if >1. Default is 1.
+          Warning: produces smoother circles but might introduce gradients that affect vision!
+
+    Returns
+    ----------
+    A stimulus dictionary with the stimulus ['img'] and target mask ['mask']
+    """
+    stim = circular_white(
+        visual_size=visual_size,
+        ppd=ppd,
+        frequency=frequency,
+        intensity_discs=intensity_discs,
+        intensity_background=intensity_background,
+        intensity_target=intensity_target,
+        target_indices=0,
+        ssf=ssf)
+    return stim
+
+
 def radial_white(
     visual_size=(10, 12),
     ppd=20,
@@ -247,7 +293,8 @@ def radial_white(
     from stimuli.utils import plot_stimuli
 
     stims = {
-        "Circular White's effect": circular_white(),
+        "Circular Whites": circular_white(),
+        "Circular Bullseye": circular_bullseye(),
         "Radial white": radial_white(),
     }