通过“ def compress（S）”进行图像压缩。使用游程编码的功能 [英] Image compression by "def compress(S)" function using run-length encoding

问题描述

我需要编写一个名为 compress（S）的函数，该函数需要一个长度小于以下内容的二进制字符串 S 等于64作为输入，并返回另一个二进制字符串作为输出。输出的二进制字符串应为输入字符串的游程长度编码。

I need to write a function called compress(S) that takes a binary string S of length less than or equal to 64 as input and returns another binary string as output. The output binary string should be a run-length encoding of the input string.

游程长度编码按序列（称为游程序列）表示图像）的8位字节：

Run-length coding represents an image by a sequence (called a "run-length sequence") of 8-bit bytes:

每个字节的第一位代表将在图像中显示的下一位，即0或1。
最后七个位包含在图像的当前位置连续出现的那些位的二进制数。

The first bit of each byte represents the bit that will appear next in the image, either 0 or 1. The final seven bits contain the number in binary of those bits that appear consecutively at the current location in the image.

>>>compress( 64*'0' )
'01000000'
>>> compress( '11111' )
'10000101'
>>> Stripes = '0'*16 + '1'*16 + '0'*16 + '1'*16
>>> compress(Stripes)
'00010000100100000001000010010000'

推荐答案

首次运行长度编码，将其定义为-

First Run Length Encoding, define it as-

def rle(input_string):
            """ takes input as string and checks repeating bit
                return repeating bit with their counts.
            """
            count = 1
            prev = ''
            lst = []
            for character in input_string:
                if character != prev:
                    if prev:
                        entry = (prev,count)
                        lst.append(entry)
                        #print lst
                    count = 1
                    prev = character
                else:
                    count += 1
            else:
                entry = (character,count)
                lst.append(entry)

            return lst

生成元组列表。

输入：print rle（'1111010'）

Input: print rle('1111010')

输出：[（'1'，4）， （'0'，1），（'1'，1），（'0'，1）]

Output: [('1', 4), ('0', 1), ('1', 1), ('0', 1)]

 ----------------------------------

现在使用此列表制作具有重复计数的二进制转换的字典，并将其格式化为7位长。最后添加字典的相应键和值，以便总位数保持8位。

Now use this list to make dictionary with binary conversion of repeating counts and format it to 7 bits long. And finally add the respective key and values of the dict so that total digit remain 8 bits.

def new_dict(S):
            """ input of rle(S) i.e., tuples of bit and repeating counts
                output dict as bit as key and value as counts with binary conversion.
            """  

            dict=rle(S)
            new_dict = []
            temp = []
            for k,v in dict:
                temp = k + "%07d" % int(bin(v)[2:])
                new_dict.append(temp)
            return new_dict

输入：打印new_dict（'1111010'）

input: print new_dict('1111010')

输出：['10000100'，'00000001'，'10000001'，'00000001']

output: ['10000100', '00000001', '10000001', '00000001']

现在使用compress（S）函数压缩此二进制字符串。

Now compress this binary string with the compress(S) function.

        def compress(S):
            """ takes a binary string S of length less than or equal to 64 as input and returns another binary string as output. 
            """
            l = new_dict(S)
            return''.join(str(elem) for elem in l)

打印压缩（'1111010'）

打印压缩（64 *'0'）

print compress('1111010')
print compress( 64*'0' )

print compress（'11111'）

print compress( '11111' )

条纹='0'* 16 +'1'* 16 +'0'* 16 +'1'* 16

Stripes = '0'*16 + '1'*16 + '0'*16 + '1'*16

打印压缩（条纹）

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