寫入.PGM圖像會導致無法定向的形狀

Question

我正在嘗試讀取並重新寫入PGM圖像，但它會導致無法定向的形狀。右邊的圖像是原單，左邊是重新創建一個：

這是代碼我使用：

#include <iostream> 
#include <string> 
#include <fstream> 
#include <sstream> 

using namespace std; 

int main() 
{ 
int row = 0, col = 0, num_of_rows = 0, max_val = 0; 
stringstream data; 
ifstream image ("3.pgm"); 

string inputLine = ""; 

getline (image, inputLine); // read the first line : P5 
data << image.rdbuf(); 
data >> row >> col >> max_val; 
cout << row << " " << col << " " << max_val << endl; 
static float array[11000][5000] = {}; 
unsigned char pixel ; 

for (int i = 0; i < row; i++) 
{ 
    for (int j = 0; j < col; j++) 
    { 
     data >> pixel; 
     array[j][i] = pixel; 



    } 
} 

ofstream newfile ("z.pgm"); 
newfile << "P5 " << endl << row << " " << col << " " << endl << max_val << endl; 

for (int i = 0; i < row; i++) 
{ 
    for (int j = 0; j < col; j++) 
    { 

     pixel = array[j][i]; 

     newfile << pixel; 


    } 

} 

image.close(); 
newfile.close(); 
} 

我究竟做錯了什麼？

the original image header

Answer 1

@Lightness種族在軌道是正確的。您需要將數據讀取爲二進制數據。你也混合了行和列：寬度是col，高度是行。你也不需要一個stringstream。

打開image爲二進制文件：
ifstream image("3.pgm", ios::binary);

閱讀所有的頭信息：在二進制數據
vector< vector<unsigned char> > array(row, vector<unsigned char>(col));

閱讀：
image >> inputLine >> col >> row >> max_val;

創建一個行X山坳矩陣：

for (int i = 0; i < row; i++) 
    for (int j = 0; j < col; j++) 
     image.read(reinterpret_cast<char*>(&array[i][j]), 1); 

或

for (int i = 0; i < row; i++) 
    image.read(reinterpret_cast<char*>(&array[i][0]), col); 

打開輸出文件，在二進制模式：
ofstream newfile("z.pgm", ios::binary);

寫頭信息： newfile << "P5" << endl << col << " " << row << endl << max_val << endl;

寫出二進制數據：

for (int i = 0; i < row; i++) 
    for (int j = 0; j < col; j++) 
     newfile.write(reinterpret_cast<const char*>(&array[i][j]), 1); 

或

for (int i = 0; i < row; i++) 
    newfile.write(reinterpret_cast<const char*>(&array[i][0]), col);