Question

I need help setting up a function that inputs a ppm file and flips it horizontally in the output in C++ using a 1D vector

Answer 1

#include <stdio.h>
#include <stdlib.h>

//i have taken a 1D array as input. All you need to do here is take the ppm file and find its height and width, The function to flip horizontally will remain the same.
//So basically here we are taking a single dimensional array.
/*1 2 3 4
5 6 7 8
9 10 11 12 */
//consider this as an input.
void fliphorizontally(int a[],int width,int height)
{
   int i=0;
   while(i<height) //we will run the code depending on the height.
   {
       int length=((2*i+1)*width)/2; //This takes the middle of each row. According to the height and then flip it.
       int count=0; //We have this to make sure where the count is at present.
       for(int j=i*width;j<length;j++)
       {
           int temp=a[j];
           a[j]=a[width*(i+1)-1-count]; //We use it to flip each row.
           a[width*(i+1)-1-count]=temp;
           count++;  
       }
       i++;
   }      
}
int main()
{
   int n=12,width=4,height=3; //Just for your reference i have inputted a width and a height of the ppm file.
   int a[]={1,2,3,4,5,6,7,8,9,10,11,12}; //i have taken an input of pixels for u to understand.
   fliphorizontally(a,width,height);
   for(int i=0;i<n;i++) //I have inputted the file after flipping.
   {
       printf("%d ",a[i]);
   }
}
//Hope i could be of help