Introduction to 2D Linux Game Programming/Algorithms/Simple Software Transformations/90° Image Rotation

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90° Image Rotation[edit]

In 2D games it's often necessary to rotate an image by 90 degrees. This algorithm does so quickly and easily.

The Source:[edit]

// Rotate90.cpp
#include <iostream>
#include "include/S.h"
#include <string>
#include <sstream>
using namespace std;
 
int main()
{
	// All rotations are clockwise
	// rotate = 0 - do nothing
	// rotate = 1 - rotate 90
	// rotate = 2 - rotate 180
	// rotate = 3 - rotate 270
	// const int rotate;
        const int width = S::sw();         // The original Array's width
	cout << "\n";
        const int height = S::sh(width);   // The original Array's height
	const int widthheight = width * height;
	int source[widthheight];
	int dest[widthheight];
	int rotate;
 
        for(int x = 0; x < widthheight; x++)
                source[x]=x;
 
	cout << "\n\n";
	S::print_rect(width, height, &source[0]);
 
	cout << "\nTo rotate clockwise by 0   degrees enter 0."
	     << "\nTo rotate clockwise by 90  degrees enter 1."
	     << "\nTo rotate clockwise by 180 degrees enter 2."
	     << "\nTo rotate clockwise by 270 degrees enter 3: ";
	cin >> rotate;	
	cout << "\n\n";
 
	switch(rotate)
	{
		// Do nothing
		case 0:
			S::print_rect(width, height, &source[0]);
			break;
 
		// Rotate 90
		case 1:
			for(int h = 0, dest_col = height - 1; h < height; ++h, --dest_col)
			{
				for(int w = 0; w < width; w++)
				{
					dest[ ( w * height ) + dest_col] = source[h*width + w];
				}
			}
 
			S::print_rect(height, width, &dest[0]);
			break;
 
		// Rotate 180
		case 2:
			for( int h=0, dest_row=(height-1); h < height; --dest_row, ++h )
			{
				for ( int w=0, dest_col=(width-1); w < width; ++w, --dest_col )
				{
					dest[ dest_row * width + dest_col] = source[h*width + w];
				}
			}
 
			S::print_rect(width, height, &dest[0]);
			break;
 
		// Rotate 270
		case 3:
			for(int h = 0, dest_col=0; h < height; ++dest_col, ++h)
			{
				for(int w=0, dest_row=width-1; w < width; --dest_row, ++w)
				{
					dest[(dest_row * height) + dest_col] = source[ h * width + w];
				}
			}
 
			S::print_rect(height, width, &dest[0]);
			break;
 
		// Out of range, do nothing
		default:
			break;
	}
 
	cout << endl;
	return 0;
}