Add image paint and POV examples

Author: PaintYourDragon

examples/dotstar_image_paint.py

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+#!/usr/bin/python3
+
+# Light-painting example for Adafruit DotStar RGB LED strip.
+# Loads image, displays column-at-a-time on LEDs at a reasonable
+# speed for long exposure photography.
+# See dotstar_simpletest.py for a much simpler example script.
+# See dotstar_image_pov.py for a faster persistence-of-vision example.
+
+import time
+from PIL import Image
+import board
+import adafruit_dotstar as dotstar
+
+NUMPIXELS = 30         # Number of LEDs in strip
+FILENAME = 'hello.png' # Image file to load
+
+# First two arguments in strip declaration identify the clock and data pins
+# (here we're using the hardware SPI pins). Last argument identifies the
+# color order -- older DotStar strips use GBR instead of BRG.
+DOTS = dotstar.DotStar(board.SCK, board.MOSI, NUMPIXELS, brightness=0.25,
+                       auto_write=False, pixel_order=dotstar.BGR)
+
+# Load image in RGB format and get dimensions:
+print('Loading...')
+IMG = Image.open(FILENAME).convert("RGB")
+PIXELS = IMG.load()
+WIDTH = IMG.size[0]
+HEIGHT = IMG.size[1]
+print('%dx%d pixels' % IMG.size)
+
+if HEIGHT > NUMPIXELS:
+    HEIGHT = NUMPIXELS
+
+# Calculate gamma correction table, makes mid-range colors look 'right':
+GAMMA = bytearray(256)
+for i in range(256):
+    GAMMA[i] = int(pow(float(i) / 255.0, 2.7) * 255.0 + 0.5)
+
+print('Displaying...')
+while True:                      # Loop forever
+
+    for x in range(WIDTH):       # For each column of image...
+        for y in range(HEIGHT):  # For each pixel in column...
+            value = PIXELS[x, y] # Read pixel in image
+            DOTS[y] = (          # Set pixel #y in strip
+                GAMMA[value[0]], # Gamma-corrected red
+                GAMMA[value[1]], # Gamma-corrected green
+                GAMMA[value[2]]) # Gamma-corrected blue
+        DOTS.show()              # Refresh LED strip
+        time.sleep(0.01)         # Pause 1/100 sec.
+
+    DOTS.fill(0)                 # Clear strip and pause 1/4 sec.
+    DOTS.show()
+    time.sleep(0.25)

examples/dotstar_image_pov.py

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+#!/usr/bin/python3
+
+# Persistence-of-vision (POV) example for Adafruit DotStar RGB LED strip.
+# Loads image, displays column-at-a-time on LEDs at very high speed,
+# suitable for naked-eye illusions.
+# See dotstar_simpletest.py for a much simpler example script.
+# See dotstar_image_paint.py for a slightly simpler light painting example.
+# This code accesses some elements of the dotstar object directly rather
+# than through function calls or setters/getters...this is poor form as it
+# could break easily with future library changes, but is the only way right
+# now to do the POV as quickly as possible.
+
+from PIL import Image
+import board
+import adafruit_dotstar as dotstar
+
+NUMPIXELS = 30         # Length of DotStar strip
+FILENAME = 'hello.png' # Image file to load
+ORDER = dotstar.BGR    # Change to GBR for older DotStar strips
+
+# First two arguments in strip declaration identify the clock and data pins
+# (here we're using the hardware SPI pins).
+DOTS = dotstar.DotStar(board.SCK, board.MOSI, NUMPIXELS, auto_write=False,
+                       brightness=0.25, pixel_order=ORDER)
+
+# Load image in RGB format and get dimensions:
+print('Loading...')
+IMG = Image.open(FILENAME).convert('RGB')
+PIXELS = IMG.load()
+WIDTH = IMG.size[0]
+HEIGHT = IMG.size[1]
+print('%dx%d pixels' % IMG.size)
+
+if HEIGHT > NUMPIXELS:
+    HEIGHT = NUMPIXELS
+
+# Calculate gamma correction table, makes mid-range colors look 'right':
+GAMMA = bytearray(256)
+for i in range(256):
+    # Notice we access DOTS.brightness directly here...the gamma table will
+    # handle any brightness-scaling, so we can set the object brightness back
+    # to max and it won't need to perform brightness scaling on every write.
+    GAMMA[i] = int(pow(float(i) / 255.0, 2.7) * DOTS.brightness * 255.0 + 0.5)
+DOTS.brightness = 1.0
+
+# Allocate list of bytearrays, one for each column of image.
+# Each pixel REQUIRES 4 bytes (0xFF, B, G, R).
+print('Allocating...')
+COLUMN = [0 for x in range(WIDTH)]
+for x in range(WIDTH):
+    COLUMN[x] = bytearray(HEIGHT * 4)
+
+# Convert entire RGB image into column-wise bytearray list.
+# The dotstar_image_paint.py example uses the library's 'setter' operation
+# for each pixel to do any R/G/B reordering.  Because we're preparing data
+# directly for the strip, there's a reference to 'ORDER' here to rearrange
+# the color bytes as needed.
+print('Converting...')
+for x in range(WIDTH):                             # For each column of image
+    for y in range(HEIGHT):                        # For each pixel in column
+        value = PIXELS[x, y]                       # Read RGB pixel in image
+        y4 = y * 4                                 # Position in raw buffer
+        COLUMN[x][y4] = 0xFF                       # Pixel start marker
+        y4 += 1                                    # Pixel color data start
+        COLUMN[x][y4 + ORDER[0]] = GAMMA[value[0]] # Gamma-corrected R
+        COLUMN[x][y4 + ORDER[1]] = GAMMA[value[1]] # Gamma-corrected G
+        COLUMN[x][y4 + ORDER[2]] = GAMMA[value[2]] # Gamma-corrected B
+
+print('Displaying...')
+while True:                                 # Loop forever
+
+    # pylint: disable=protected-access
+    # (Really shouldn't access _buf directly, but needed for fastest POV)
+    for x in range(WIDTH):                  # For each column of image...
+        DOTS._buf[4:4+HEIGHT*4] = COLUMN[x] # Copy column to DotStar buffer
+        DOTS.show()                         # Send data to strip