Here I’ve discussed a very simple way to Rotate Image by 90 degree in C++ Programming.

Consider an image as a 2-Dimensional Array or 2-D matrix which can be stored in a Buffer.

We are given “base address” and dimension of Matrix.

Suppose we have an Image like this:

* * * | * * * * * * | * * * * * * | * * * * * * | * * *

So after turning it by 90 degree we will have it like this:

* * * * * * * * * * * * - - - - * * * * * * * * * * * *

## Now here is the Program to RotateĀ Image by 90 Degree in C++:

#include <iostream> #include <stdlib.h> using namespace std; void displayMatrix(unsigned int const *p, unsigned int row, unsigned int col); void rotate(unsigned int *pS, unsigned int *pD, unsigned int row, unsigned int col); int main() { // declarations unsigned int image[][4] = {{1,2,3,4}, {5,6,7,8}, {9,10,11,12}}; unsigned int *pSource; unsigned int *pDestination; unsigned int m, n; // setting initial values and memory allocation m = 3, n = 4, pSource = (unsigned int *)image; pDestination = (unsigned int *)malloc(sizeof(int)*m*n); // process each buffer displayMatrix(pSource, m, n); rotate(pSource, pDestination, m, n); displayMatrix(pDestination, n, m); free(pDestination); getchar(); return 0; } void displayMatrix(unsigned int const *p, unsigned int r, unsigned int c) { unsigned int row, col; cout<<"nn"; for(row = 0; row < r; row++) { for(col = 0; col < c; col++) { cout<<"t"<<*(p + row * c + col); } cout<<"n"; } cout<<"nn"; } void rotate(unsigned int *pS, unsigned int *pD, unsigned int row, unsigned int col) { unsigned int r, c; for(r = 0; r < row; r++) { for(c = 0; c < col; c++) { *(pD + c * row + (row - r - 1)) = *(pS + r * col + c); } } }

Here’s an easier to understand version…

void rotate(size_t y, size_t x, char src[y][x], char dst[x][y]) {

int i, j;

for (i = 0;i < x;i++) {

for (j = 0;j < y;j++) {

dst[i][j] = src[y-j-1][i];

}

}

}