84 lines
2.1 KiB
C++
84 lines
2.1 KiB
C++
// ==============================================================
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// This file is part of the Glest Advanced Engine
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//
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// Copyright (C) 2010 James McCulloch <silnarm at gmail>
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//
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// You can redistribute this code and/or modify it under
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// the terms of the GNU General Public License as published
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// by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version
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// ==============================================================
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#ifndef _LINE_ALGORITHM_INCLUDED_
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#define _LINE_ALGORITHM_INCLUDED_
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#include <cassert>
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namespace Shared { namespace Util {
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/** midpoint line algorithm, 'Visit' specifies the 'pixel visit' function, *
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* and must take two int params (x & y co-ords) */
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template<typename VisitFunc> void line(int x0, int y0, int x1, int y1, VisitFunc visitor) {
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bool mirror_x, mirror_y;
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int pivot_x, pivot_y;
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if (x0 > x1) {
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mirror_x = true;
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pivot_x = x0;
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x1 = (x0 << 1) - x1;
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} else {
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mirror_x = false;
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}
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if (y0 > y1) {
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mirror_y = true;
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pivot_y = y0;
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y1 = (y0 << 1) - y1;
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} else {
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mirror_y = false;
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}
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// Visit(x,y) => Visit(mirror_x ? (pivot_x << 1) - x : x, mirror_y ? (pivot_y << 1) - y : y);
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assert(y0 <= y1 && x0 <= x1);
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int dx = x1 - x0,
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dy = y1 - y0;
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int x = x0,
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y = y0;
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if (dx == 0) {
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while (y <= y1) {
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visitor(mirror_x ? (pivot_x << 1) - x : x, mirror_y ? (pivot_y << 1) - y : y);
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++y;
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}
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} else if (dy == 0) {
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while (x <= x1) {
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visitor(mirror_x ? (pivot_x << 1) - x : x, mirror_y ? (pivot_y << 1) - y : y);
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++x;
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}
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} else if (dy > dx) {
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int d = 2 * dx - dy;
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int incrS = 2 * dx;
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int incrSE = 2 * (dx - dy);
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do {
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visitor(mirror_x ? (pivot_x << 1) - x : x, mirror_y ? (pivot_y << 1) - y : y);
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if (d <= 0) {
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d += incrS; ++y;
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} else {
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d += incrSE; ++x; ++y;
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}
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} while (y <= y1);
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} else {
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int d = 2 * dy - dx;
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int incrE = 2 * dy;
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int incrSE = 2 * (dy - dx);
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do {
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visitor(mirror_x ? (pivot_x << 1) - x : x, mirror_y ? (pivot_y << 1) - y : y);
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if (d <= 0) {
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d += incrE; ++x;
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} else {
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d += incrSE; ++x; ++y;
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}
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} while (x <= x1);
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}
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}
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}} // end namespace Shared::Util
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#endif // !def _LINE_ALGORITHM_INCLUDED_
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