adafruitlightpaint4pi.py

#!/usr/bin/python

# Light painting / POV demo for Raspberry Pi using
# Adafruit Digital Addressable RGB LED flex strip.
# ----> http://adafruit.com/products/306

import RPi.GPIO as GPIO, Image, time

# Configurable values
filename  = "hello.png"
dev       = "/dev/spidev0.0"

# Open SPI device, load image in RGB format and get dimensions:
spidev    = file(dev, "wb")
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
# To do: add resize here if image is not desired height

# Calculate gamma correction table.  This includes
# LPD8806-specific conversion (7-bit color w/high bit set).
gamma = bytearray(256)
for i in range(256):
	gamma[i] = 0x80 | int(pow(float(i) / 255.0, 2.5) * 127.0 + 0.5)

# Create list of bytearrays, one for each column of image.
# R, G, B byte per pixel, plus extra '0' byte at end for latch.
print "Allocating..."
column = [0 for x in range(width)]
for x in range(width):
	column[x] = bytearray(height * 3 + 1)

# Convert 8-bit RGB image into column-wise GRB bytearray list.
print "Converting..."
for x in range(width):
	for y in range(height):
		value = pixels[x, y]
		y3 = y * 3
		column[x][y3]     = gamma[value[1]]
		column[x][y3 + 1] = gamma[value[0]]
		column[x][y3 + 2] = gamma[value[2]]


# Then it's a trivial matter of writing each column to the SPI port.
print "Displaying..."
while True:
	for x in range(width):
                spidev.write(column[x])
                spidev.flush()
		time.sleep(0.001)
	time.sleep(0.5)