C :操纵PPM文件的问题

我正在研究一个可以在ppm文件上执行各种效果和操纵的程序。但是，出于测试原因，它使用CIN而不是输入文件。它应该能够一次执行多种效果，但是我什至很难做到。我将在将有效的行上运行一个removeBlue（），然后以不同的值重试，然后将其删除红色或绿色。之类的东西。有很多代码，所以我将尝试仅包括必要的内容。

#include <vector>
#include <stdlib.h>
#include <cstdlib>
#include <string>
#include <vector>
#include <fstream>
#include <sstream>
#include <iostream>
using namespace std;
class SimpleImageEffect
{
public:
    virtual void processImage(vector<Point> &points) = 0;
};
class RemoveRed : public SimpleImageEffect
{
public:
    virtual void processImage(vector<Point> &points)
    {
        for (Point& p : points)
        {
            p.setRed(0);
        }
    }
};
//Just an example of one of the effect classes. 
//The code in them is correct, so I won't include the others unless needed.
vector<Point> parse_line(string line)
{
    istringstream scanner{line};
    vector<Point> result{};
    int red = -1;
    int green = -1;
    int blue = -1;
    int counter = 0;
    while(scanner.good())
    {
        if (counter == 0)
        {
            counter++;
            scanner >> red;
        }
        else if (counter == 1)
        {
            counter++;
            scanner >> green;
        }
        else if (counter == 2)
        {
            scanner >> blue;
            Point p{ red, green, blue };
            result.push_back(p);
            counter = 0;
        }
    }
    return result;
}
void readFromCin()
{
    string line = "";
    vector<string> lines_in_file{};
    int i, effect_choice;
    SimpleImageEffect *effect = nullptr;
    getline(cin, line);
    while (line.length() > 0)
    {
        lines_in_file.push_back(line);
        getline(cin, line);
    }
    for (int i = 0; i < lines_in_file.size(); i++)
    {
        if (lines_in_file[i] != "P3")
        {
            effect_choice = strToInt(lines_in_file[i]);
        }
        else if (lines_in_file[i] == "P3")
        {
            cout << lines_in_file[i] << endl;
            cout << lines_in_file[i+1] << endl;
            cout << lines_in_file[i+2] << endl;
        }
        vector<Point> points = parse_line(lines_in_file[i]);
        if (effect_choice == 1) effect = new RemoveRed;
        if (effect_choice == 2) effect = new RemoveGreen;
        if (effect_choice == 3) effect = new RemoveBlue;
        if (effect_choice == 4) effect = new NegateRed;
        if (effect_choice == 5) effect = new NegateGreen;
        if (effect_choice == 6) effect = new NegateBlue;
        if (effect_choice == 7) effect = new AddNoise;
        if (effect_choice == 8) effect = new HighContrast;
        if (effect_choice == 9) effect = new ConvertToGrayscale;
        effect->processImage(points);
        for (auto p : points)
        {
            cout << p;
            cout << endl;
        }
    }
}
int main(int argc, char** argv)
{
    string menu_choice;
    getline(cin, menu_choice);
    if (menu_choice == "1")
    {
        readFromFile();
    }
    else
    {
        readFromCin();
    }
    return 0;
}

因此，以

2
1
P3
1 1
255
50 50 50

将返回

P3
1 1
255
0 50 50

，但是如果我用

2
3
P3
1 2
255
50 50 50
1 2 3

它返回

P3
1 2
255
0 50 50
0 2 3

我绝对不知道是什么原因引起了问题，因此，任何帮助都将不胜感激。谢谢。