Add a polar plot example and some minor corrections to other examples. (

#20)

README.md

@@ -18,7 +18,7 @@ updates, and so on.
 
 <img src="./pico-tempe-polar.png" width="480" alt="A Raspberry Pi Pico with a variety of polar plots on the screen" /> <img src="./docs/source/user_guide/polar.png" width="160" alt="A variety of polar plots drawn in an image" />
 
-<img src="./docs/source/user_guide/line_plot_4.png" width="160" alt="A line plot of temperature over time drawn in an image" /> <img src="./docs/source/user_guide/scatter_plot.png" width="160" alt="A scatter plot of environmental data with scales drawn in an image" />
+<img src="./docs/source/user_guide/line_plot_4.png" width="160" alt="A line plot of temperature over time drawn in an image" /> <img src="./docs/source/user_guide/scatter_plot.png" width="160" alt="A scatter plot of environmental data with scales drawn in an image" /> <img src="./docs/source/user_guide/polar_plot.png" width="160" alt="A polar plot of air quality data over time in an image" />
 
 ## Documentation
 

examples/polar_plots.py

@@ -0,0 +1,211 @@
+from array import array
+import gc
+from math import sqrt, log
+
+from tempe import colors
+from tempe.colormaps.viridis import viridis
+from tempe.data_view import Range, Repeat
+from tempe.geometry import ColumnGeometry, RowGeometry, PointsToLines
+from tempe.markers import Marker
+from tempe.polar_geometry import polar_points, polar_r_lines
+from tempe.surface import Surface
+
+
+surface = Surface()
+
+# a buffer one third the size of the screen
+working_buffer = array('H', bytearray(2*320*81))
+
+
+# fill the background with off-white pixels
+surface.rects('BACKGROUND', [(0, 0, 320, 240)], [colors.grey_1])
+
+class LinearScale:
+    """Object that maps data to screen values linearly."""
+
+    def __init__(self, low_data, low_screen, high_data, high_screen):
+        self.low_data = low_data
+        self.low_screen = low_screen
+        self.high_data = high_data
+        self.high_screen = high_screen
+        data_range = high_data - low_data
+        screen_range = high_screen - low_screen
+        self.scale = screen_range / data_range
+
+    def scale_values(self, data):
+        """Scale data values to screen values."""
+        screen = array('h', bytearray(2*len(data)))
+        low_data = self.low_data
+        low_screen = self.low_screen
+        scale = self.scale
+        for i, value in enumerate(data):
+            screen[i] = int(low_screen + scale * (value - low_data))
+        return screen
+
+class ColorScale:
+    """Object that maps data to color values."""
+
+    def __init__(self, colormap, low_data, low_screen, high_data, high_screen):
+        self.colormap = colormap
+        self.low_data = low_data
+        self.low_screen = low_screen
+        self.high_data = high_data
+        self.high_screen = high_screen
+        data_range = high_data - low_data
+        screen_range = high_screen - low_screen
+        self.scale = screen_range / data_range
+
+    def scale_values(self, data):
+        """Scale data values to screen values."""
+        screen = array('h', bytearray(2*len(data)))
+        low_data = self.low_data
+        low_screen = self.low_screen
+        scale = self.scale
+        colormap = self.colormap
+        max_color = len(colormap) - 1
+        for i, value in enumerate(data):
+            screen[i] = colormap[max(
+                min(
+                    int(low_screen + scale * (value - low_data)),
+                    max_color,
+                ),
+                0,
+            )]
+        return screen
+
+gc.collect()
+from data.environmental import timestamps, air_quality
+
+# Plot screen bounds
+cx = 160
+cy = 120
+max_r = 100
+
+# Map the data to polar coordinates
+air_quality_scale = LinearScale(0, 0, 150, max_r)
+time_scale = LinearScale(1729551600, -90, 1729638000, 270)
+color_scale = ColorScale(viridis, 1729500000, 0, 1729500000+48*60*60, 255)
+
+thetas = time_scale.scale_values(timestamps)
+line_colors = color_scale.scale_values(timestamps)
+quality_rs = air_quality_scale.scale_values(air_quality)
+
+# Create polar line geometry for the data points
+quality_lines = PointsToLines(polar_points(cx, cy, ColumnGeometry([quality_rs, thetas])))
+gc.collect()
+
+# draw the plot
+surface.lines(
+    "DRAWING",
+    quality_lines,
+    line_colors,
+    clip=(cx - max_r, cy - max_r, 2*max_r+1, 2*max_r+1),
+)
+
+quality_label_values = [50, 100, 150]
+quality_label_rs = air_quality_scale.scale_values(quality_label_values)
+time_label_values = [1729551600 + i*3600 for i in range(6, 24, 6)]
+time_label_strings = ["9:00", "12:00", "18:00"]
+time_label_thetas = time_scale.scale_values(time_label_values)
+time_label_rs = [max_r + 8, max_r + 8, max_r + 40]
+
+surface.circles(
+    "UNDERLAY",
+    ColumnGeometry([
+        Repeat(cx),
+        Repeat(cy),
+        quality_label_rs,
+    ]),
+    Repeat(colors.grey_3),
+    fill=False,
+    clip=(cx - max_r, cy - max_r, 2*max_r+1, 2*max_r+1),
+)
+surface.lines(
+    "UNDERLAY",
+    polar_r_lines(cx, cy, ColumnGeometry([
+        Repeat(air_quality_scale.scale_values([50])[0]),
+        time_scale.scale_values([1729551600 + 3600*i for i in range(24)]),
+        Repeat(int(air_quality_scale.scale * 100)),
+    ])),
+    Repeat(colors.grey_3),
+    clip=(cx - max_r, cy - max_r, 2*max_r+1, 2*max_r+1),
+)
+
+quality_label_geometry = polar_points(cx, cy, ColumnGeometry([quality_label_rs, Repeat(270)]))
+surface.points(
+    "OVERLAY",
+    quality_label_geometry,
+    Repeat(colors.grey_6),
+    [f" {value:d} ppb" for value in quality_label_values],
+    clip=(cx, cy - max_r - 8, 64, 100),
+)
+time_label_geometry = polar_points(
+    cx,
+    cy,
+    ColumnGeometry([time_label_rs, time_label_thetas]),
+)
+surface.points(
+    "OVERLAY",
+    time_label_geometry,
+    Repeat(colors.grey_6),
+    time_label_strings,
+    clip=(0, 0, 320, 240),
+)
+
+# Plot title and additional information
+from tempe.fonts import roboto16bold, roboto16
+from tempe.font import TempeFont
+surface.text(
+    'DRAWING',
+    [[4, 0]],
+    [colors.grey_7],
+    ["Air Quality (ppb)"],
+    font=TempeFont(roboto16bold),
+)
+surface.text(
+    'DRAWING',
+    [[4, 20]],
+    [colors.grey_6],
+    ["20/8/24--\n22/8/24"],
+    font=TempeFont(roboto16),
+)
+
+def main(surface, working_buffer):
+    import asyncio
+
+    async def init_display():
+        from devices.st7789 import ST7789
+        from machine import Pin, SPI
+
+        spi = SPI(0, baudrate=62_500_000, phase=1, polarity=1, sck=Pin(18, Pin.OUT), mosi=Pin(19, Pin.OUT), miso=Pin(16, Pin.OUT))
+        backlight = Pin(20, Pin.OUT)
+        display = ST7789(spi, cs_pin=Pin(17, Pin.OUT, value=1), dc_pin=Pin(16, Pin.OUT))
+        backlight(1)
+        await display.init()
+        return display
+
+    # set up the display object
+    display = asyncio.run(init_display())
+
+    # refresh the display
+    display.clear()
+    import time
+    start = time.ticks_us()
+    surface.refresh(display, working_buffer)
+    print(time.ticks_diff(time.ticks_us(), start))
+
+
+if __name__ == '__main__':
+
+#     # if we have an actual screen, use it
+#     main(surface, working_buffer)
+
+# elif __name__ != '__test__':
+    from tempe.display import FileDisplay
+
+    # set up the display object
+    display = FileDisplay('polar_plot.rgb565', (320, 240))
+    # refresh the display
+    with display:
+        display.clear()
+        surface.refresh(display, working_buffer)

examples/scatter_plot.py

@@ -159,7 +159,7 @@ def scale_values(self, data):
 marker_sizes = humidity_scale.scale_values(humidity)
 marker_colors = time_scale.scale_values(timestamps)
 
-# Create line geometry for the data points
+# Create point-size geometry for the data points
 markers = ColumnGeometry([xs, ys, marker_sizes])
 
 # draw the plot
@@ -366,14 +366,14 @@ async def init_display():
 
 if __name__ == '__main__':
 
-    # if we have an actual screen, use it
-    main(surface, working_buffer)
+#     # if we have an actual screen, use it
+#     main(surface, working_buffer)
 
-elif __name__ != '__test__':
+# elif __name__ != '__test__':
     from tempe.display import FileDisplay
 
     # set up the display object
-    display = FileDisplay('line_plot.rgb565', (320, 240))
+    display = FileDisplay('scatter_plot.rgb565', (320, 240))
     # refresh the display
     with display:
         display.clear()