extremely_fast_line_algorithm.c

// Extremely Fast Line Algorithm Var E (Addition Fixed Point PreCalc)
// Copyright 2001-2, By Po-Han Lin


// Freely useable in non-commercial applications as long as credits 
// to Po-Han Lin and link to http://www.edepot.com is provided in 
// source code and can been seen in compiled executable.  
// Commercial applications please inquire about licensing the algorithms.
//
// Lastest version at http://www.edepot.com/phl.html
// This version is for standard displays (up to 65536x65536)
// For small display version (256x256) visit http://www.edepot.com/lineex.html

// used by myLine
void myPixel(SURFACE* surface, int x,int y) {
  // PLOT x,y point on surface

}


// THE EXTREMELY FAST LINE ALGORITHM Variation E (Addition Fixed Point PreCalc)
void myLine(SURFACE* surface, int x, int y, int x2, int y2) {
   	bool yLonger=false;
	int shortLen=y2-y;
	int longLen=x2-x;
	if (abs(shortLen)>abs(longLen)) {
		int swap=shortLen;
		shortLen=longLen;
		longLen=swap;				
		yLonger=true;
	}
	int decInc;
	if (longLen==0) decInc=0;
	else decInc = (shortLen << 16) / longLen;

	if (yLonger) {
		if (longLen>0) {
			longLen+=y;
			for (int j=0x8000+(x<<16);y<=longLen;++y) {
				myPixel(surface,j >> 16,y);	
				j+=decInc;
			}
			return;
		}
		longLen+=y;
		for (int j=0x8000+(x<<16);y>=longLen;--y) {
			myPixel(surface,j >> 16,y);	
			j-=decInc;
		}
		return;	
	}

	if (longLen>0) {
		longLen+=x;
		for (int j=0x8000+(y<<16);x<=longLen;++x) {
			myPixel(surface,x,j >> 16);
			j+=decInc;
		}
		return;
	}
	longLen+=x;
	for (int j=0x8000+(y<<16);x>=longLen;--x) {
		myPixel(surface,x,j >> 16);
		j-=decInc;
	}

}

void mySquare(SURFACE* surface,int x, int y, int x2, int y2) {
	myLine(surface,x,y,x2,y2);
	myLine(surface,x2,y2,x2+(y-y2),y2+(x2-x));
	myLine(surface,x,y,x+(y-y2),y+(x2-x));
	myLine(surface,x+(y-y2),y+(x2-x),x2+(y-y2),y2+(x2-x));
}


void myRect(SURFACE* surface, int x, int y, int x2, int y2) {
	myLine(surface,x,y,x2,y);
	myLine(surface,x2,y,x2,y2);
	myLine(surface,x2,y2,x,y2);
	myLine(surface,x,y2,x,y);
}