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Add a rate limiter on the slicer's index #24

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merged 11 commits into from
Dec 2, 2020
Merged

Add a rate limiter on the slicer's index #24

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77471f9
Add a rate limiter on the slicer index
almarklein Nov 25, 2020
c9cbaf1
dont use reverse_y=False in the examples
almarklein Nov 25, 2020
bd5c0ca
Refactoring
almarklein Nov 25, 2020
c2e0759
prevent updating title, just in case
almarklein Nov 25, 2020
4f17523
more refactoring/cleaning and disable cache for now
almarklein Nov 25, 2020
2a4af1c
fix ci
almarklein Nov 25, 2020
6cbbbf3
make two stores part of public API, plus add notes on performance
almarklein Nov 26, 2020
d799063
set update_title=None in most our examples
almarklein Nov 26, 2020
539dc90
remove caching code and tweak docstrings
almarklein Nov 27, 2020
7d1807d
remove convenience function again
almarklein Nov 27, 2020
1082986
Update dash_slicer/slicer.py
almarklein Dec 1, 2020
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228 changes: 152 additions & 76 deletions dash_slicer/slicer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
from plotly.graph_objects import Figure
from dash import Dash
from dash.dependencies import Input, Output, State, ALL
from dash_core_components import Graph, Slider, Store
from dash_core_components import Graph, Slider, Store, Interval

from .utils import img_array_to_uri, get_thumbnail_size, shape3d_to_size2d

Expand All @@ -26,6 +26,7 @@ class VolumeSlicer:
reverse_y (bool): Whether to reverse the y-axis, so that the origin of
the slice is in the top-left, rather than bottom-left. Default True.
(This sets the figure's yaxes ``autorange`` to "reversed" or True.)
Note: setting this to False affects performance, see #12.
scene_id (str): the scene that this slicer is part of. Slicers
that have the same scene-id show each-other's positions with
line indicators. By default this is derived from ``id(volume)``.
Expand All @@ -51,9 +52,13 @@ class VolumeSlicer:
The value in the store must be an 3-element tuple (x, y, z) in scene coordinates.
To apply the position for one position only, use e.g ``(None, None, x)``.

Some notes on performance: for a smooth experience, create the `Dash`
application with `update_title=None`, and when running the server in debug
mode, consider setting `dev_tools_props_check=False`.
Some notes on performance: for a smooth experience, avoid triggering
unnecessary figure updates. When adding a callback that uses the
slicer position, use the (rate limited) `index` and `pos` stores
rather than the slider value. Further, create the `Dash` application
with `update_title=None`, and when running the server in debug mode,
consider setting `dev_tools_props_check=False`.

"""

_global_slicer_counter = 0
Expand Down Expand Up @@ -154,6 +159,20 @@ def stores(self):
"""
return self._stores

@property
def index(self):
"""A dcc.Store containing the integer slice number. This value
is a rate-limited version of the slider value.
"""
return self._index

@property
def pos(self):
"""A dcc.Store containing the float position in scene coordinates,
along the slice-axis.
"""
return self._pos

@property
def overlay_data(self):
"""A dcc.Store containing the overlay data. The form of this
Expand Down Expand Up @@ -275,63 +294,107 @@ def _create_dash_components(self):
config={"scrollZoom": True},
)

# Create a slider object that the user can put in the layout (or not)
initial_index = info["size"][2] // 2
initial_pos = info["origin"][2] + initial_index * info["spacing"][2]

# Create a slider object that the user can put in the layout (or not).
# Note that the tooltip introduces a measurable performance penalty,
# so maybe we can display it in a different way?
self._slider = Slider(
id=self._subid("slider"),
min=0,
max=info["size"][2] - 1,
step=1,
value=info["size"][2] // 2,
tooltip={"always_visible": False, "placement": "left"},
value=initial_index,
updatemode="drag",
tooltip={"always_visible": False, "placement": "left"},
)

# Create the stores that we need (these must be present in the layout)

# A dict of static info for this slicer
self._info = Store(id=self._subid("info"), data=info)
self._position = Store(
id=self._subid("position", True, axis=self._axis), data=0
)
self._setpos = Store(id=self._subid("setpos", True), data=None)
self._requested_index = Store(id=self._subid("req-index"), data=0)
self._request_data = Store(id=self._subid("req-data"), data="")

# A list of low-res slices (encoded as base64-png)
self._lowres_data = Store(id=self._subid("lowres"), data=thumbnails)

# A list of mask slices (encoded as base64-png or null)
self._overlay_data = Store(id=self._subid("overlay"), data=[])

# Slice data provided by the server
self._server_data = Store(id=self._subid("server-data"), data="")

# Store image traces for the slicer.
self._img_traces = Store(id=self._subid("img-traces"), data=[])

# Store indicator traces for the slicer.
self._indicator_traces = Store(id=self._subid("indicator-traces"), data=[])

# A timer to apply a rate-limit between slider.value and index.data
self._timer = Interval(id=self._subid("timer"), interval=100, disabled=True)

# The (integer) index of the slice to show. This value is rate-limited
self._index = Store(id=self._subid("index"), data=initial_index)

# The (float) position (in scene coords) of the current slice,
# used to publish our position to slicers with the same scene_id.
self._pos = Store(
id=self._subid("pos", True, axis=self._axis), data=initial_pos
)

# Signal to set the position of other slicers with the same scene_id.
self._setpos = Store(id=self._subid("setpos", True), data=None)

self._stores = [
self._info,
self._position,
self._setpos,
self._requested_index,
self._request_data,
self._lowres_data,
self._overlay_data,
self._server_data,
self._img_traces,
self._indicator_traces,
self._timer,
self._index,
self._pos,
self._setpos,
]

def _create_server_callbacks(self):
"""Create the callbacks that run server-side."""
app = self._app

@app.callback(
Output(self._request_data.id, "data"),
[Input(self._requested_index.id, "data")],
Output(self._server_data.id, "data"),
[Input(self._index.id, "data")],
)
def upload_requested_slice(slice_index):
slice = img_array_to_uri(self._slice(slice_index))
return {"index": slice_index, "slice": slice}

def _create_client_callbacks(self):
"""Create the callbacks that run client-side."""

# setpos (external)
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This is some serious Ascii art :-)

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I'm eager for better ways to use diagrams to document code. In the mean time, ASCII art it is :)

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http://blockdiag.com/en/ maybe... (usable as a sphinx extension from a "sphinx documentation diagram" Google search :-), did not investigate more).

# \
# slider --[rate limit]--> index --> pos
# \ \
# \ server_data (a new slice)
# \ \
# \ --> image_traces
# ----------------------- / \
# -----> figure
# /
# indicator_traces
# /
# pos (external)

app = self._app

# ----------------------------------------------------------------------
# Callback to trigger fellow slicers to go to a specific position.
# Callback to trigger fellow slicers to go to a specific position on click.

app.clientside_callback(
"""
function trigger_setpos(data, index, info) {
function update_setpos_from_click(data, index, info) {
if (data && data.points && data.points.length) {
let point = data["points"][0];
let xyz = [point["x"], point["y"]];
Expand All @@ -348,11 +411,11 @@ def _create_client_callbacks(self):
)

# ----------------------------------------------------------------------
# Callback to update index from external setpos signal.
# Callback to update slider based on external setpos signals.

app.clientside_callback(
"""
function respond_to_setpos(positions, cur_index, info) {
function update_slider_value(positions, cur_index, info) {
for (let trigger of dash_clientside.callback_context.triggered) {
if (!trigger.value) continue;
let pos = trigger.value[2 - info.axis];
Expand All @@ -379,64 +442,81 @@ def _create_client_callbacks(self):
)

# ----------------------------------------------------------------------
# Callback to update position (in scene coordinates) from the index.
# Callback to rate-limit the index (using a timer/interval).

app.clientside_callback(
"""
function update_position(index, info) {
return info.origin[2] + index * info.spacing[2];
}
""",
Output(self._position.id, "data"),
[Input(self._slider.id, "value")],
[State(self._info.id, "data")],
)
function update_index_rate_limiting(index, n_intervals, interval) {

# ----------------------------------------------------------------------
# Callback to request new slices.
# Note: this callback cannot be merged with the one below, because
# it would create a circular dependency.
if (!window._slicer_{{ID}}) window._slicer_{{ID}} = {};
let slicer_state = window._slicer_{{ID}};
let now = window.performance.now();

app.clientside_callback(
"""
function update_request(index) {
// Get whether the slider was moved
let slider_was_moved = false;
for (let trigger of dash_clientside.callback_context.triggered) {
if (trigger.prop_id.indexOf('slider') >= 0) slider_was_moved = true;
}

// Clear the cache?
if (!window.slicecache_for_{{ID}}) { window.slicecache_for_{{ID}} = {}; }
let slice_cache = window.slicecache_for_{{ID}};
// Initialize return values
let req_index = dash_clientside.no_update;
let disable_timer = false;

// Request a new slice (or not)
let request_index = index;
if (slice_cache[index]) {
return window.dash_clientside.no_update;
} else {
console.log('requesting slice ' + index);
return index;
// If the slider moved, remember the time when this happened
slicer_state.new_time = slicer_state.new_time || 0;

if (slider_was_moved) {
slicer_state.new_time = now;
} else if (!n_intervals) {
disable_timer = true; // start disabled
}

// We can either update the rate-limited index interval ms after
// the real index changed, or interval ms after it stopped
// changing. The former makes the indicators come along while
// dragging the slider, the latter is better for a smooth
// experience, and the interval can be set much lower.
if (index != slicer_state.req_index) {
if (now - slicer_state.new_time >= interval) {
req_index = slicer_state.req_index = index;
disable_timer = true;
console.log('requesting slice ' + req_index);
}
}

return [req_index, disable_timer];
}
""".replace(
"{{ID}}", self._context_id
),
Output(self._requested_index.id, "data"),
[Input(self.slider.id, "value")],
[
Output(self._index.id, "data"),
Output(self._timer.id, "disabled"),
],
[Input(self._slider.id, "value"), Input(self._timer.id, "n_intervals")],
[State(self._timer.id, "interval")],
)

# ----------------------------------------------------------------------
# Callback that creates a list of image traces (slice and overlay).
# Callback to update position (in scene coordinates) from the index.

app.clientside_callback(
"""
function update_image_traces(index, req_data, overlays, lowres, info, current_traces) {
function update_pos(index, info) {
return info.origin[2] + index * info.spacing[2];
}
""",
Output(self._pos.id, "data"),
[Input(self._index.id, "data")],
[State(self._info.id, "data")],
)

// Add data to the cache if the data is indeed new
if (!window.slicecache_for_{{ID}}) { window.slicecache_for_{{ID}} = {}; }
let slice_cache = window.slicecache_for_{{ID}};
for (let trigger of dash_clientside.callback_context.triggered) {
if (trigger.prop_id.indexOf('req-data') >= 0) {
slice_cache[req_data.index] = req_data;
break;
}
}
# ----------------------------------------------------------------------
# Callback that creates a list of image traces (slice and overlay).

app.clientside_callback(
"""
function update_image_traces(index, server_data, overlays, lowres, info, current_traces) {

// Prepare traces
let slice_trace = {
Expand All @@ -453,14 +533,14 @@ def _create_client_callbacks(self):
overlay_trace.hovertemplate = '';
let new_traces = [slice_trace, overlay_trace];

// Depending on the state of the cache, use full data, or use lowres and request slice
if (slice_cache[index]) {
let cached = slice_cache[index];
slice_trace.source = cached.slice;
// Use full data, or use lowres
if (index == server_data.index) {
slice_trace.source = server_data.slice;
} else {
slice_trace.source = lowres[index];
// Scale the image to take the exact same space as the full-res
// version. It's not correct, but it looks better ...
// version. Note that depending on how the low-res data is
// created, the pixel centers may not be correctly aligned.
slice_trace.dx *= info.size[0] / info.lowres_size[0];
slice_trace.dy *= info.size[1] / info.lowres_size[1];
slice_trace.x0 += 0.5 * slice_trace.dx - 0.5 * info.spacing[0];
Expand All @@ -472,7 +552,7 @@ def _create_client_callbacks(self):
if (new_traces[0].source == current_traces[0].source &&
new_traces[1].source == current_traces[1].source)
{
new_traces = window.dash_clientside.no_update;
new_traces = dash_clientside.no_update;
}
return new_traces;
}
Expand All @@ -481,8 +561,8 @@ def _create_client_callbacks(self):
),
Output(self._img_traces.id, "data"),
[
Input(self.slider.id, "value"),
Input(self._request_data.id, "data"),
Input(self._slider.id, "value"),
Input(self._server_data.id, "data"),
Input(self._overlay_data.id, "data"),
],
[
Expand All @@ -495,12 +575,9 @@ def _create_client_callbacks(self):
# ----------------------------------------------------------------------
# Callback to create scatter traces from the positions of other slicers.

# Create a callback to create a trace representing all slice-indices that:
# * corresponding to the same volume data
# * match any of the selected axii
app.clientside_callback(
"""
function handle_indicator(positions1, positions2, info, current) {
function update_indicator_traces(positions1, positions2, info, current) {
let x0 = info.origin[0], y0 = info.origin[1];
let x1 = x0 + info.size[0] * info.spacing[0], y1 = y0 + info.size[1] * info.spacing[1];
x0 = x0 - info.spacing[0], y0 = y0 - info.spacing[1];
Expand Down Expand Up @@ -534,7 +611,7 @@ def _create_client_callbacks(self):
{
"scene": self._scene_id,
"context": ALL,
"name": "position",
"name": "pos",
"axis": axis,
},
"data",
Expand All @@ -560,7 +637,6 @@ def _create_client_callbacks(self):
for (let trace of indicators) { traces.push(trace); }

// Update figure
console.log("updating figure");
let figure = {...ori_figure};
figure.data = traces;

Expand Down
2 changes: 1 addition & 1 deletion examples/bring_your_own_slider.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
import imageio


app = dash.Dash(__name__)
app = dash.Dash(__name__, update_title=None)

vol = imageio.volread("imageio:stent.npz")
slicer = VolumeSlicer(app, vol)
Expand Down
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