feat: discrete transfer functions

ipyvolume/pylab.py

@@ -3,6 +3,8 @@
 from __future__ import absolute_import
 from __future__ import division
 import pythreejs
+from typing import List, Union
+
 
 __all__ = [
     'current',
@@ -29,6 +31,7 @@
     'animation_control',
     'gcc',
     'transfer_function',
+    'transfer_function_discrete',
     'plot_isosurface',
     'volshow',
     'save',
@@ -894,6 +897,48 @@ def gcc():
     return current.container
 
 
+def transfer_function_discrete(
+    n,
+    colors: List[str] = ["red", "green", "blue"],
+    labels: Union[None, List[str]] = None,
+    opacity: Union[float, List[float]] = 0.1,
+    enabled: Union[bool, List[bool]] = True,
+    controls=True,
+):
+    """Create a discrete transfer function with n layers.
+
+    Each (integer) value of the volumetric data maps to a single color.
+
+    :param n: number of layers
+    :param colors: list of colors, can be any valid HTML color string
+    :param labels: list of labels, if None, labels will be "Layer 0", "Layer 1", etc.
+    :param opacity: opacity of each layer, can be a single value or a list of values
+    :param enabled: whether each layer is enabled, can be a single value or a list of values
+    :param controls: whether to add the controls to the current container
+
+    """
+    if isinstance(opacity, float):
+        opacity = [opacity] * len(colors)
+    if isinstance(enabled, bool):
+        enabled = [enabled] * len(colors)
+
+    def ensure_length(x):
+        repeat = (n + len(colors) - 1) // len(colors)
+        return (x * repeat)[:n]
+
+    if labels is None:
+        labels = []
+        for i in range(n):
+            labels.append(f"Layer {i}")
+
+    tf = ipv.TransferFunctionDiscrete(colors=ensure_length(colors), opacities=ensure_length(opacity), enabled=ensure_length(enabled), labels=ensure_length(labels))
+    gcf()  # make sure a current container/figure exists
+    if controls:
+        current.container.children = [tf.control()] + current.container.children
+
+    return tf
+
+
 def transfer_function(
     level=[0.1, 0.5, 0.9], opacity=[0.01, 0.05, 0.1], level_width=0.1, controls=True, max_opacity=0.2
 ):
@@ -1029,8 +1074,7 @@ def volshow(
 ):
     """Visualize a 3d array using volume rendering.
 
-    Currently only 1 volume can be rendered.
-
+    If the data is of type int8 or bool, :any:`a discrete transfer function will be used <ipv.discrete_transfer_function>`
 
     :param data: 3d numpy array
     :param origin: origin of the volume data, this is to match meshes which have a different origin
@@ -1040,7 +1084,7 @@ def volshow(
     :param float data_max: maximum value to consider for data, if None, computed using np.nanmax
     :parap int max_shape: maximum shape for the 3d cube, if larger, the data is reduced by skipping/slicing (data[::N]),
                           set to None to disable.
-    :param tf: transfer function (or a default one)
+    :param tf: transfer function (or a default one, based on the data)
     :param bool stereo: stereo view for virtual reality (cardboard and similar VR head mount)
     :param ambient_coefficient: lighting parameter
     :param diffuse_coefficient: lighting parameter
@@ -1060,12 +1104,18 @@ def volshow(
     """
     fig = gcf()
 
-    if tf is None:
-        tf = transfer_function(level, opacity, level_width, controls=controls, max_opacity=max_opacity)
     if data_min is None:
         data_min = np.nanmin(data)
     if data_max is None:
         data_max = np.nanmax(data)
+    if tf is None:
+        if (data.dtype == np.uint8) or (data.dtype == bool):
+            if data.dtype == bool:
+                data_max = 1
+
+            tf = transfer_function_discrete(n=data_max + 1)
+        else:
+            tf = transfer_function(level, opacity, level_width, controls=controls, max_opacity=max_opacity)
     if memorder == 'F':
         data = data.T
 

ipyvolume/test_all.py

@@ -9,6 +9,7 @@
 import pytest
 
 import ipyvolume
+import ipyvolume as ipv
 import ipyvolume.pylab as p3
 import ipyvolume as ipv
 import ipyvolume.examples
@@ -303,6 +304,14 @@ def test_volshow():
     p3.save("tmp/ipyolume_volume.html")
 
 
+def test_volshow_discrete():
+    boolean_volume = np.random.random((10, 10, 10)) > 0.5
+    ipv.figure()
+    vol = ipv.volshow(boolean_volume)
+    assert isinstance(vol.tf, ipyvolume.TransferFunctionDiscrete)
+    assert len(vol.tf.colors) == 2
+    # int8_volume = np.random.randint(0, 255, size=(10, 10, 10), dtype=np.uint8)
+
 def test_volshow_max_shape():
     x, y, z = ipyvolume.examples.xyz(shape=32)
     Im = x * y * z

ipyvolume/transferfunction.py

@@ -2,7 +2,7 @@
 
 from __future__ import absolute_import
 
-__all__ = ['TransferFunction', 'TransferFunctionJsBumps', 'TransferFunctionWidgetJs3', 'TransferFunctionWidget3']
+__all__ = ['TransferFunction', 'TransferFunctionDiscrete', 'TransferFunctionJsBumps', 'TransferFunctionWidgetJs3', 'TransferFunctionWidget3']
 
 import numpy as np
 import ipywidgets as widgets  # we should not have widgets under two names
@@ -12,6 +12,7 @@
 
 import ipyvolume._version
 from ipyvolume import serialize
+import ipyvuetify as v
 
 
 N = 1024
@@ -26,11 +27,29 @@ class TransferFunction(widgets.DOMWidget):
     _model_module = Unicode('ipyvolume').tag(sync=True)
     _view_module = Unicode('ipyvolume').tag(sync=True)
     style = Unicode("height: 32px; width: 100%;").tag(sync=True)
+    # rgba should be a 2d array of shape (N, 4), where the last dimension is the rgba value
+    # with values between 0 and 1
     rgba = Array(default_value=None, allow_none=True).tag(sync=True, **serialize.ndarray_serialization)
     _view_module_version = Unicode(semver_range_frontend).tag(sync=True)
     _model_module_version = Unicode(semver_range_frontend).tag(sync=True)
 
 
+class TransferFunctionDiscrete(TransferFunction):
+    _model_name = Unicode('TransferFunctionDiscreteModel').tag(sync=True)
+    colors = traitlets.List(traitlets.Unicode(), default_value=["red", "#0f0"]).tag(sync=True)
+    opacities = traitlets.List(traitlets.CFloat(), default_value=[0.01, 0.01]).tag(sync=True)
+    enabled = traitlets.List(traitlets.Bool(), default_value=[True, True]).tag(sync=True)
+    labels = traitlets.List(traitlets.Unicode(), default_value=["label1", "label2"]).tag(sync=True)
+
+    def control(self):
+        return TransferFunctionDiscreteView(tf=self)
+
+
+class TransferFunctionDiscreteView(v.VuetifyTemplate):
+    template_file = (__file__, 'vue/tf_discrete.vue')
+    tf = traitlets.Instance(TransferFunctionDiscrete).tag(sync=True, **widgets.widget_serialization)
+
+
 class TransferFunctionJsBumps(TransferFunction):
     _model_name = Unicode('TransferFunctionJsBumpsModel').tag(sync=True)
     _model_module = Unicode('ipyvolume').tag(sync=True)

js/src/tf.ts

@@ -3,6 +3,8 @@ import * as widgets from "@jupyter-widgets/base";
 import {default as ndarray_pack} from "ndarray-pack";
 import * as serialize from "./serialize.js";
 import {semver_range} from "./utils";
+import _ from "underscore";
+import * as THREE from "three";
 
 export
 class TransferFunctionView extends widgets.DOMWidgetView {
@@ -112,6 +114,53 @@ class TransferFunctionJsBumpsModel extends TransferFunctionModel {
     }
 }
 
+export
+class TransferFunctionDiscreteModel extends TransferFunctionModel {
+
+    constructor(...args) {
+        super(...args);
+        this.on("change:colors", this.recalculate_rgba, this);
+        this.on("change:opacities", this.recalculate_rgba, this);
+        this.on("change:enabled", this.recalculate_rgba, this);
+        this.recalculate_rgba();
+    }
+    defaults() {
+        return {
+            ...super.defaults(),
+            _model_name : "TransferFunctionDiscreteModel",
+            color: ["red", "#0f0"],
+            opacities: [0.01, 0.01],
+            enabled: [true, true],
+        };
+    }
+
+    recalculate_rgba() {
+        const rgba = [];
+        const colors = _.map(this.get("colors"), (color : string) => {
+            return (new THREE.Color(color)).toArray();
+        });
+        const enabled = this.get("enabled");
+        const opacities = this.get("opacities");
+        (window as any).rgba = rgba;
+        (window as any).tfjs = this;
+        const N = colors.length;
+        for (let i = 0; i < N; i++) {
+            const color = [...colors[i], opacities[i]]; // red, green, blue and alpha
+            color[3] = Math.min(1, color[3]); // clip alpha
+            if(!enabled[i]) {
+                color[3] = 0;
+            }
+            rgba.push(color);
+        }
+        // because we want the shader to sample the center pixel, if we add one extra pixel in the texture
+        // all samples should be shiften by epsilon so the sample the center of the transfer function
+        rgba.push([0, 0, 0, 0]);
+        const rgba_array = ndarray_pack(rgba);
+        this.set("rgba", rgba_array);
+        this.save_changes();
+    }
+}
+
 export
 class TransferFunctionWidgetJs3Model extends TransferFunctionModel {