huffman for image

Author: sundeshgupta

huffman_image.cpp

@@ -0,0 +1,113 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+struct pixel{
+	float freq;
+	int label;
+	pixel* left, *right;
+
+	pixel(int x, float y):	label(x), freq(y){
+		left = NULL;
+		right = NULL;
+	}
+
+	void print(){
+		cout << label << " " << freq << endl;
+	}
+};
+
+struct compare{
+	bool operator() (pixel* a, pixel* b){
+		return a->freq > b->freq;
+	}
+};
+
+string code[256];
+
+void preoder(pixel* root, string s){
+	
+	if(root->label != -1){
+		cout << setfill(' ') << setw(3) << root->label 
+			<< " -> " << setw(15) << s << setw(20) << fixed << setprecision(8) << root->freq << endl;  
+		code[root->label] = s; 
+		return;
+	}
+
+	preoder(root->left, s + '0');
+	preoder(root->right, s + '1');
+
+	return;
+}
+
+
+int main()
+{
+	int width, height, bpp;
+
+	uint8_t* rgb_image = stbi_load("/home/sundesh/Downloads/colombia.jpg", &width, &height, &bpp, 1);
+
+	int image[height][width];
+	int itr = 0;
+	for (int i = 0; i < height; ++i)
+		for (int j = 0; j < width; ++j)
+			image[i][j] = rgb_image[itr++];
+
+	stbi_image_free(rgb_image);	
+
+	int hist[256] = {0}; 
+	  
+	for (int i = 0; i < height; i++) 
+	    for (int j = 0; j < width; j++) 
+	        hist[image[i][j]] += 1;
+
+	int totpix = height*width;
+
+	float freq[256] = {0};
+	
+	for (int i = 0; i < 256; ++i)
+		freq[i] = ((float)hist[i])/totpix;
+
+
+
+	priority_queue<pixel*, vector<pixel*>, compare> pq;
+
+	for(int i = 0; i < 256; i++){
+		if (freq[i] > 0){
+			pixel* tmp = new pixel(i, freq[i]);
+			pq.push(tmp);
+		}
+	}
+
+	while(pq.size() > 1){
+		pixel* first = pq.top();
+		pq.pop();
+		pixel* second = pq.top();
+		pq.pop();
+		pixel* tmp = new pixel(-1, first->freq + second->freq);
+		tmp->left = first;
+		tmp->right = second;
+		pq.push(tmp);
+	}
+
+	pixel* root = pq.top();
+
+	preoder(root, "");
+	
+	int compression_size = 0;
+
+	for (int i = 0;i < height; ++i)
+	{
+		for (int j = 0; j < width; ++j)
+		{
+			compression_size += code[image[i][j]].size();
+		}
+	}
+
+	cout << compression_size << " " << 256*256*8 << endl;
+
+
+	return 0;
+}
+