void Graph::halfTone(Color color){
int megaPixel = 3;
Vector v;
Color tmp;
int numberOfPixels;
//backup before doing half-toning
backupPixelBuffer();
for(int r = 0 ; r < window_height; r+=megaPixel){ //row
for(int c = 0 ; c < window_width; c+=megaPixel){//col
v = {0,0,0};
for(int i = r; i < r+megaPixel ; i++){ // 3 by 3
for(int j = c; j < c+megaPixel; j++ ){
//DPRINT("r %d, c %d, i %d, j %d\n", r, c, i,j);
tmp = readPixel(j,i);
if( equal(tmp, background_color) )
v = add( v, {1, 1, 1} );
else
v = add( v, ctov( tmp ) );
}
}
//write each mega pixel
numberOfPixels = round( 9- (v.x + v.y + v.z) / 3 );
drawMegaPixel(numberOfPixels, megaPixel * 3, r, c, color);
}
}
}
// This is a Bresenham-based linescan function using mega pixels
// All cases use similar structure to the standard case, just with different values for dFa, dFb, and p
void loeschLineScanMega(My2DPoint p1, My2DPoint p2) {
if (p1.x > p2.x) // if the points are in the wrong order, swap them first
swapPoints(p1, p2);
// declare and initialize values
int dY = p2.y - p1.y;
int dX = p2.x - p1.x;
float m = (float)dY / (float)dX; // calculate and store slope
int dFa;
int dFb;
int p;
int currX = 0;
int currY = 0;
if (dX == 0) { // vertical line
if (p1.y < p2.y) { // if p1 is lower, draw starting from p1
for (int i = 0; i < dY - (dY % 5); i += 5)
drawMegaPixel(p1.x, p1.y + i);
}
else // otherwise draw starting from p2
{
for (int i = 0; i < dY - (dY % 5); i += 5)
drawMegaPixel(p2.x, p2.y + i);
}
}
else if (m >= 0.0 && m <= 1.0) { // standard case ( 0 <= m <= 1 )
// calculate dFa and dFb, as well as the initial value for p
dFa = 10 * dY - 10 * dX;
dFb = 10 * dY;
p = 10 * dY - 5 * dX;
// draw the initial point
drawMegaPixel(p1.x, p1.y);
for (int k = 5; k <= dX - (dX % 5); k += 5) { // k is the current x value
if (p < 0) // if p is below the midpoint, use dFb
p += dFb;
else { // otherwise p is above midpoint, use dFa
currY += 5;
p += dFa;
}
drawMegaPixel(p1.x + k, p1.y + currY); // draw a pixel at the current x and y
}
}
else if (m > 1.0) { // slope greater than 1 ( m < 1 )
dFa = 10 * (dX - dY);
dFb = 10 * dX;
p = 10 * dX - 5 * dY;
drawMegaPixel(p1.x, p1.y);
for (int k = 5; k <= dY - (dY % 5); k += 5) { // k is the current y value
if (p < 0)
p += dFb;
else {
currX += 5;
p += dFa;
}
drawMegaPixel(p1.x + currX, p1.y + k);
}
}
else if (m < 0.0 && m >= -1.0) { // negative slope ( 0 < m <= -1 )
dFa = 10 * (dY + dX);
dFb = 10 * dY;
p = 10 * dY + 5 * dX;
drawMegaPixel(p1.x, p1.y);
for (int k = 5; k <= dX - (dX % 5); k += 5) { // k is the current x value
if (p > 0)
p += dFb;
else {
currY += 5;
p += dFa;
}
drawMegaPixel(p1.x + k, p1.y - currY);
}
}
else { // slope must be negative and less than -1 ( m < -1 )
dY *= -1; // make dY positive (in order to emulate the case m < 1)
dFa = 10 * (dX - dY);
dFb = 10 * dX;
p = 10 * dX - 5 * dY;
drawMegaPixel(p1.x, p1.y);
for (int k = 5; k <= dY - (dY % 5); k += 5) { // k is the current y value
if (p < 0)
p += dFb;
else {
currX += 5;
p += dFa;
}
drawMegaPixel(p1.x + currX, p1.y - k);
}
}
}
