adding encode.py. This file is used for encoding messages

encode.py

+import math
+from PIL import Image
+
+
+def encodeLzw(uncompressed):
+    dict_size = 256
+    dictionary = {}
+    for i in range(dict_size):
+        dictionary[chr(i)] = i
+
+    w = ""
+    for c in uncompressed:
+        wc = w + c
+        if wc in dictionary:
+            w = wc
+        else:
+            encoded_version.append(dictionary[w])
+            dictionary[wc] = dict_size
+            dict_size += 1
+            w = c
+
+    if w:
+        encoded_version.append(dictionary[w])
+
+    # appending length of list as first element
+    N = len(encoded_version)
+    encoded_version.append(N)
+    encoded_version[0], encoded_version[N] = encoded_version[N], encoded_version[0]
+
+
+encoded_version = []
+
+# int length is taken to be 16 bits
+if __name__ == "__main__":
+    input_string = input("Enter a string to encode: ")
+    encodeLzw(input_string)
+    encoded_bin_version = []  # final list to insert in image each entry is 16-bit string
+    for i in range(0, len(encoded_version)):
+        current_string = '{0:016b}'.format(encoded_version[i])
+        for j in range(0, 8):  # parsing current string into 8 parts
+            encoded_bin_version.append(current_string[2 * j:2 * j + 2])
+
+    ctr = 0
+    n = len(encoded_bin_version) - 1
+
+    im = Image.open('input.png')
+    pixelMap = im.load()
+
+    img = Image.new(im.mode, im.size)
+    pixelsNew = img.load()
+
+    for i in range(0, img.size[0]):
+        for j in range(0, img.size[1]):
+            if ctr > n:
+                pixelsNew[i, j] = pixelMap[i, j]
+            else:
+                original_pixel = pixelMap[i, j][0]  # changing the value of red pixel
+                encoded_pixel = 4 * math.floor(original_pixel / 4) + int(encoded_bin_version[ctr], 2)
+                pixelsNew[i, j] = (encoded_pixel, pixelMap[i, j][1], pixelMap[i, j][2])
+                ctr = ctr + 1
+
+    img.save('output.png')
+    img.close()
+    im.close()