將任何彩色PPM圖像轉換爲僅有8種顏色的彩色圖像

Question

我需要一種算法將ppm格式的任何彩色圖像轉換爲C++中只有8種顏色。我嘗試此代碼，我一直面臨着一個錯誤與>>和<<運營商：

#include "stdafx.h" 
    #include<iostream> 
    #include<fstream> 
    using namespace std; 

    int main() 
    { 
ifstream in; 
in.open("football.ppm"); 
ofstream out("football8color.ppm"); 

string header; 
int cols, rows,colors; 
int r, g, b; 


in >> header >> cols >> rows >> colors; 
out << header << endl; 
out<< cols<< " " << rows <<endl; 
out<< colors<< endl; 

for (int i=0; i<rows; i++) 
{ 
    for (int j=0; j<cols; j++){ 
     in>> r >> g >> b; 
} 
out <<endl; 
    } 
    in.close(); 
    out.close(); 
    return 0 ; 
    } 

我得到這些錯誤：

4 IntelliSense: no operator "<<" matches these operands c:\users\atiyeh\documents\visual studio 2010\projects\mm ass 2\mm ass 2\mm ass 2.cpp 18 
    3 IntelliSense: no operator ">>" matches these operands c:\users\atiyeh\documents\visual studio 2010\projects\mm ass 2\mm ass 2\mm ass 2.cpp 17 
Error 2 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion) c:\users\atiyeh\documents\visual studio 2010\projects\mm ass 2\mm ass 2\mm ass 2.cpp 16 
Error 1 error C2678: binary '>>' : no operator found which takes a left-hand operand of type 'std::ifstream' (or there is no acceptable conversion) c:\users\atiyeh\documents\visual studio 2010\projects\mm ass 2\mm ass 2\mm ass 2.cpp 15 

Answer 1

對於算法，你應該看看了Color Quantization。如果你想使它看起來不錯，你應該查找dithering技術，如Floyd-Stienberg抖動。