Move graphics compression routines to new module

piker/ui/_compression.py

@@ -0,0 +1,129 @@
+# piker: trading gear for hackers
+# Copyright (C) Tyler Goodlet (in stewardship for pikers)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import numpy as np
+from numba import (
+    jit, float64, optional, int64,
+)
+
+
+def downsample(
+    x: np.ndarray,
+    y: np.ndarray,
+    bins: int,
+    method: str = 'peak',
+
+) -> tuple[np.ndarray, np.ndarray]:
+    '''
+    Downsample x/y data for lesser curve graphics gen.
+
+    The "peak" method is originally copied verbatim from
+    ``pyqtgraph.PlotDataItem.getDisplayDataset()``.
+
+    '''
+    # py3.10 syntax
+    match method:
+        case 'peak':
+            ds = bins
+            n = len(x) // ds
+            x1 = np.empty((n, 2))
+            # start of x-values; try to select a somewhat centered point
+            stx = ds//2
+            x1[:] = x[stx:stx+n*ds:ds, np.newaxis]
+            x = x1.reshape(n*2)
+            y1 = np.empty((n, 2))
+            y2 = y[:n*ds].reshape((n, ds))
+            y1[:, 0] = y2.max(axis=1)
+            y1[:, 1] = y2.min(axis=1)
+            y = y1.reshape(n*2)
+
+        case '4px':
+
+            # Ex. from infinite on downsampling viewable graphics.
+            # "one thing i remembered about the binning - if you are
+            # picking a range within your timeseries the start and end bin
+            # should be one more bin size outside the visual range, then
+            # you get better visual fidelity at the edges of the graph"
+            # "i didn't show it in the sample code, but it's accounted for
+            # in the start and end indices and number of bins"
+
+            def build_subchart(
+                self,
+                subchart,
+                width,  # width of screen?
+                chart_type,
+                lower,  # x start?
+                upper,  # x end?
+                xvals,
+                yvals
+            ):
+                pts_per_pixel = len(xvals) / width
+                if pts_per_pixel > 1:
+
+                    # this is mutated in-place
+                    data = np.zeros((width, 4), yvals.dtype)
+                    bins = np.zeros(width, xvals.dtype)
+
+                    nb = subset_by_x(
+                        xvals,
+                        yvals,
+                        bins,
+                        data,
+                        lower,
+                        # this is scaling the x-range by
+                        # the width of the screen?
+                        (upper-lower)/float(width),
+                    )
+
+    return x, y
+
+
+@jit(nopython=True)
+def subset_by_x(
+
+    xs: np.ndarray,
+    ys: np.ndarray,
+    bins: np.ndarray,
+    data: np.ndarray,
+    x_start: int,
+    step: float,
+
+) -> int:
+    count = len(xs)
+    # nbins = len(bins)
+    bincount = 0
+    x_left = start
+    # Find the first bin
+    while xs[0] >= x_left + step:
+        x_left += step
+    bins[bincount] = x_left
+    data[bincount] = ys[0]
+
+    for i in range(count):
+        x = xs[i]
+        y = ys[i]
+        if x < x_left + step:   # Interval is [bin, bin+1)
+            data[bincount, 1] = min(y, data[bincount, 1])
+            data[bincount, 2] = max(y, data[bincount, 2])
+            data[bincount, 3] = y
+        else:
+            # Find the next bin
+            while x >= x_left + step:
+                x_left += step
+            bincount += 1
+            bins[bincount] = x_left
+            data[bincount] = y
+
+    return bincount

piker/ui/_curve.py

@@ -1,5 +1,5 @@
 # piker: trading gear for hackers
-# Copyright (C) Tyler Goodlet (in stewardship for piker0)
+# Copyright (C) Tyler Goodlet (in stewardship for pikers)
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published by
@@ -95,38 +95,6 @@ _line_styles: dict[str, int] = {
 }
 
 
-def downsample(
-    x: np.ndarray,
-    y: np.ndarray,
-    bins: int,
-    method: str = 'peak',
-
-) -> tuple[np.ndarray, np.ndarray]:
-    '''
-    Downsample x/y data for lesser curve graphics gen.
-
-    The "peak" method is originally copied verbatim from
-    ``pyqtgraph.PlotDataItem.getDisplayDataset()``.
-
-    '''
-    match method:
-        case 'peak':
-            ds = bins
-            n = len(x) // ds
-            x1 = np.empty((n, 2))
-            # start of x-values; try to select a somewhat centered point
-            stx = ds//2
-            x1[:] = x[stx:stx+n*ds:ds, np.newaxis]
-            x = x1.reshape(n*2)
-            y1 = np.empty((n, 2))
-            y2 = y[:n*ds].reshape((n, ds))
-            y1[:, 0] = y2.max(axis=1)
-            y1[:, 1] = y2.min(axis=1)
-            y = y1.reshape(n*2)
-
-    return x, y
-
-
 # TODO: got a feeling that dropping this inheritance gets us even more speedups
 class FastAppendCurve(pg.PlotCurveItem):
     '''
@@ -305,8 +273,6 @@ class FastAppendCurve(pg.PlotCurveItem):
                     finiteCheck=False,
                 )
 
-            path = self.path
-
             # other merging ideas:
             # https://stackoverflow.com/questions/8936225/how-to-merge-qpainterpaths
             if self._step_mode: