bresenham.c

Simple Cube plotting using frame buffers

#include <stdint.h>
//#include <stdlib.h>
#include "bresenham.h"


// Bresenham Line Algorithm

// used by myLine
void setPixel(uint32_t* restrict surface, uint32_t x,  uint32_t y, uint32_t stride) {
	// PLOT x,y point on surface
    surface[ ( y * stride ) + x ] = 0x00;
}


// Bresenham Line Algorithm
void drawLine(uint32_t* restrict surface, uint32_t x1, uint32_t y1, uint32_t x2, uint32_t y2, uint32_t stride) {
	/*
	int32_t x = 0;
	int32_t y = 0;
	int32_t error = 0;
	int32_t delta = 0;
	int32_t step = 0;
	int32_t dx = 0;
	int32_t dy = 0;
	int32_t incx = 0;
	int32_t incy = 0;
	
	x = x1;
	y = y1;
	
	dy = y2 - y1;
	dx = x2 - x1;
	
	if(dx > 0)
		incx = 1;
	else
		incx = -1;
		
	if(dy > 0)
		incy = 1;
	else
		incy = -1;
		
	if(abs(dy) < abs(dx)){
		error = -abs(dx);
		delta = 2*abs(dy);
		step = 2*error;
		while( x != 2 ){
			setPixel(surface, x, y, stride);
			x+= incx;
			error = error + delta;
			if(error > 0) {
				y += incy;
				error += step;
			}
		}
	}
	else {
		error = -abs(dy);
		delta = 2*abs(dx);
		step = 2*error;
		while( y != y2){
			setPixel(surface, x, y, stride);
			y += incy;
			error = error + delta;
			if (error > 0){
				x += incx;
				error +=step;
			}
		}
	}
	setPixel(surface, x2, y2, stride);
*/
	int		x, y;
	int		dx, dy;
	int		incx, incy;
	int		balance;


	if (x2 >= x1)
	{
		dx = x2 - x1;
		incx = 1;
	}
	else
	{
		dx = x1 - x2;
		incx = -1;
	}

	if (y2 >= y1)
	{
		dy = y2 - y1;
		incy = 1;
	}
	else
	{
		dy = y1 - y2;
		incy = -1;
	}

	x = x1;
	y = y1;

	if (dx >= dy)
	{
		dy <<= 1;
		balance = dy - dx;
		dx <<= 1;

		while (x != x2)
		{
			setPixel(surface,x, y, stride);
			if (balance >= 0)
			{
				y += incy;
				balance -= dx;
			}
			balance += dy;
			x += incx;
		} setPixel(surface,x, y, stride);
	}
	else
	{
		dx <<= 1;
		balance = dx - dy;
		dy <<= 1;

		while (y != y2)
		{
			setPixel(surface,x, y, stride);
			if (balance >= 0)
			{
				x += incx;
				balance -= dy;
			}
			balance += dx;
			y += incy;
		} setPixel(surface,x, y, stride);
	}
}