Add: Assignment no.2 2020BTEIT00029

Assignment 2/2020BTEIT00029/Huffman.py

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+import re
+import numpy as np
+from PIL import Image
+print("Huffman Compression Program")
+
+file = "compressed.png"
+my_string = np.asarray(Image.open(file), np.uint8)
+shape = my_string.shape
+a = my_string
+
+my_string = str(my_string.tolist())
+
+
+letters = []
+only_letters = []
+for letter in my_string:
+    if letter not in letters:
+        frequency = my_string.count(letter)
+        letters.append(frequency)
+        letters.append(letter)
+        only_letters.append(letter)
+
+nodes = []
+while len(letters) > 0:
+    nodes.append(letters[0:2])
+    letters = letters[2:]
+nodes.sort()
+huffman_tree = []
+huffman_tree.append(nodes)
+
+
+def combine_nodes(nodes):
+    pos = 0
+    newnode = []
+    if len(nodes) > 1:
+        nodes.sort()
+        nodes[pos].append("1")
+        nodes[pos+1].append("0")
+        combined_node1 = (nodes[pos][0] + nodes[pos+1][0])
+        combined_node2 = (nodes[pos][1] + nodes[pos+1][1])
+        newnode.append(combined_node1)
+        newnode.append(combined_node2)
+        newnodes = []
+        newnodes.append(newnode)
+        newnodes = newnodes + nodes[2:]
+        nodes = newnodes
+        huffman_tree.append(nodes)
+        combine_nodes(nodes)
+    return huffman_tree
+
+
+newnodes = combine_nodes(nodes)
+
+huffman_tree.sort(reverse=True)
+print("Huffman tree with merged pathways:")
+
+checklist = []
+for level in huffman_tree:
+    for node in level:
+        if node not in checklist:
+            checklist.append(node)
+        else:
+            level.remove(node)
+count = 0
+for level in huffman_tree:
+    print("Level", count, ":", level)
+    count += 1
+print()
+
+letter_binary = []
+if len(only_letters) == 1:
+    lettercode = [only_letters[0], "0"]
+    letter_binary.append(letter_code*len(my_string))
+else:
+    for letter in only_letters:
+        code = ""
+        for node in checklist:
+            if len(node) > 2 and letter in node[1]:
+                code = code + node[2]
+        lettercode = [letter, code]
+        letter_binary.append(lettercode)
+print(letter_binary)
+print("Binary code generated:")
+for letter in letter_binary:
+    print(letter[0], letter[1])
+
+bitstring = ""
+for character in my_string:
+    for item in letter_binary:
+        if character in item:
+            bitstring = bitstring + item[1]
+binary = "0b"+bitstring
+print("Your message as binary is:")
+
+
+uncompressed_file_size = len(my_string)*7
+compressed_file_size = len(binary)-2
+print("Your original file size was", uncompressed_file_size,
+      "bits. The compressed size is:", compressed_file_size)
+print("This is a saving of ", uncompressed_file_size-compressed_file_size, "bits")
+output = open("compressed.txt", "w+")
+print("Compressed file generated as compressed.txt")
+output = open("compressed.txt", "w+")
+print("Decoding.......")
+output.write(bitstring)
+
+bitstring = str(binary[2:])
+uncompressed_string = ""
+code = ""
+for digit in bitstring:
+    code = code+digit
+    pos = 0
+    for letter in letter_binary:
+        if code == letter[1]:
+            uncompressed_string = uncompressed_string+letter_binary[pos][0]
+            code = ""
+        pos += 1
+
+temp = re.findall(r'\d+', uncompressed_string)
+res = list(map(int, temp))
+res = np.array(res)
+res = res.astype(np.uint8)
+res = np.reshape(res, shape)
+print(res)
+print("Observe the shapes and input and output arrays are matching or not")
+print("Input image dimensions:", shape)
+print("Output image dimensions:", res.shape)
+data = Image.fromarray(res)
+data.save('original.png')
+if a.all() == res.all():
+    print("Success") 

Assignment 2/2020BTEIT00029/Observation.txt

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+1)  Original.jpg : 
+                        Dimensions: 128x128 px
+                        Size: 171.7 kB
+2) Compressed.png :
+                        Dimensions: 100x100 px 
+                        Size: 114.2 kB
+
+Performance: 
+   By calculating the Compression Ratio of the image: 
+
+                              compression ratio  = (uncompressed image size / compressed image size)
+			     =171.7/114.2
+			     =1.50
+
+
+Huffman Encoding Time Complexity:   
+
+          The time complexity for encoding each unique character based on its frequency is O(nlog n).
+Extracting minimum frequency from the priority queue takes place 2*(n-1) times and its complexity is O(log n). Thus the overall complexity is O(nlog n).
+

Assignment 2/2020BTEIT00029/Vector_Quantization.py

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+ #for working and manipulating arrays
+import numpy as np
+import scipy as sp
+# For plotting and Visualization
+import matplotlib.pyplot as plt
+
+from sklearn import cluster
+
+from PIL import Image
+
+im = Image.open("myImage.jpg")
+im = np.array(im)
+
+
+n_clusters = 5
+np.random.seed(0)
+
+X = im.reshape((-1, 1))  
+k_means = cluster.KMeans(n_clusters=n_clusters, n_init=4)
+k_means.fit(X)
+values = k_means.cluster_centers_.squeeze()
+labels = k_means.labels_
+
+# create an array from labels and values
+im_compressed = np.choose(labels, values)
+im_compressed.shape = im.shape
+
+vmin = im.min()
+vmax = im.max()
+
+# original image
+plt.figure(1, figsize=(3, 2.2))
+plt.imshow(im.astype('uint8'), cmap=plt.cm.gray, vmin=vmin, vmax=256, )
+
+# compressed image
+plt.figure(2, figsize=(3, 2.2))
+plt.imshow(im_compressed.astype('uint8'),
+           cmap=plt.cm.gray, vmin=vmin, vmax=vmax, )
+Image.fromarray((im_compressed).astype("uint8")).save("compressed.png")
+
+
+plt.show()