Day 05

Day 05/decode.py

@@ -0,0 +1,88 @@
+#!/usr/bin/python3
+
+from PIL import Image
+
+img = Image.open("barcode.png");
+pix = img.load()
+width = img.size[0]
+
+print("Image has", width, "Pixels")
+
+smallestBar = None
+barStartedAt = None
+bars = []
+
+def findBounds():
+    start = None
+    end = None
+
+    for x in range(0, width):
+        if pix[x,0] != (255,255,255):
+            end = x
+            if start is None:
+                start = x
+
+    return (start,end)
+
+def getBars(bounds):
+    start = bounds[0]
+    end =  bounds[1]
+    lastColor = pix[start,0]
+    barStartedAt = start
+    bars = []
+    for x in range(start+1,end+1):
+        if pix[x,0] != lastColor:
+            bars.append((barStartedAt, x-1, lastColor))
+            barStartedAt = x
+            lastColor = pix[x,0]
+
+    return bars
+
+def findBarWidth(bars):
+    smallest = None
+    for b in bars:
+        width = b[1]-b[0]+1
+        if smallest is None or width < smallest:
+            smallest = width
+    return smallest
+
+def getBits(bars, barWidth):
+    bits = ""
+    for b in bars:
+        width = b[1]-b[0]+1
+        numBits = width // barWidth
+        if b[2] == (255,255,255):
+            bits += "0" * numBits
+        else:
+            bits += "1" * numBits
+    return bits
+
+def getColoredBits(bars, barWidth):
+    redChannel = ""
+    greenChannel = ""
+    blueChannel = ""
+    for b in bars:
+        if b[2] == (255,255,255):
+            continue # skip
+        else:
+            width = (b[1]-b[0]+1) // barWidth
+            redChannel += chr(b[2][0])
+            greenChannel += chr(b[2][1])
+            blueChannel += chr(b[2][2])
+
+    return (redChannel, greenChannel, blueChannel)
+
+bounds = findBounds()
+width = bounds[1] - bounds[0] + 1
+print("Barcode start x=%d end x=%d width=%d" % (bounds[0], bounds[1], width))
+
+bars = getBars(bounds)
+barWidth = findBarWidth(bars)
+print("Found %d bars, smallest bar is %d pixels" % (len(bars), barWidth))
+
+# Usual deoding results in "Not the solution", so we have to adjust our getBits method
+bits = getBits(bars, barWidth)
+print("Bitstring:", bits)
+
+bitsColored = getColoredBits(bars, barWidth)
+print("Bitstring", bitsColored)