new sstv catch python script

sstvcatch.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+# Gerrit Polder, PA3BYA, Januari 2014
+# Endless loop, wait for Image change, then transmits image data
+# on 144.5 MHz using SSTV
+
+import time
+import subprocess
+import StringIO
+from PIL import Image, ImageFont, ImageDraw
+
+mycallsign = "MYCALL" # ham radio callsign
+threshold = 10
+sensitivity = 400
+DEBUG = True
+
+font = ImageFont.load_default()
+font = ImageFont.truetype("/usr/share/fonts/truetype/freefont/FreeMonoBold.ttf", 24)
+
+# Capture an image
+def captureImage():
+	command = "raspistill -w %s -h %s -t 1 -e png -o -" % (320, 256)
+	imageData = StringIO.StringIO()
+	imageData.write(subprocess.check_output(command, shell=True))
+	imageData.seek(0)
+	image = Image.open(imageData)
+	buffer = image.load()
+	imageData.close()
+	return image, buffer
+
+# transmit image in sstv
+def transmitImage(im):
+	draw = ImageDraw.Draw(im)
+	localtime = time.strftime("%b %d %Y %H:%M:%S", time.localtime(time.time()) )
+	draw.text((10, 10), mycallsign , (0,0,0), font=font)
+	draw.text((10, 220), localtime, (0,0,0), font=font)
+	im.save("/tmp/image.png")
+	command = "./pisstv /tmp/image.png 22050"
+	subprocess.call(command, shell=True)
+	command = "sudo ./pifm_sstv /tmp/image.png.wav"
+	subprocess.call(command, shell=True)
+	command = "rm /tmp/image.png*"
+	subprocess.call(command, shell=True)
+
+# grab initial image
+img, buf = captureImage()
+
+# loop forever
+while (True):
+	if (DEBUG):
+		print(time.strftime("%b %d %Y %H:%M:%S", time.localtime(time.time()) ))
+	# grab comparison image
+	imgnew, bufnew = captureImage()
+
+	# Count changed pixels
+	changedPixels = 0
+	for x in xrange(0, 320):
+		for y in xrange(0, 256):
+			# Just check red channel as it's dominant for PiCam NoIR
+			pixdiff = abs(buf[x,y][0] - bufnew[x,y][0])
+			if pixdiff > threshold:
+				changedPixels += 1
+	if (DEBUG):
+		print(changedPixels)
+
+	# Transmit an image if pixels changed
+	if changedPixels > sensitivity:
+		# Swap comparison buffers
+		img = imgnew
+		buf = bufnew
+		transmitImage(img.copy())
+