126 lines
3.5 KiB
C
126 lines
3.5 KiB
C
/*
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* Fill a triangle.
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* Code ported from AdaFruit TFT LCD library.
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*
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* Copyright (C) 2015 Serge Vakulenko, <serge@vak.ru>
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*
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* Permission to use, copy, modify, and distribute this software
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* and its documentation for any purpose and without fee is hereby
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* granted, provided that the above copyright notice appear in all
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* copies and that both that the copyright notice and this
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* permission notice and warranty disclaimer appear in supporting
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* documentation, and that the name of the author not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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*
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* The author disclaim all warranties with regard to this
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* software, including all implied warranties of merchantability
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* and fitness. In no event shall the author be liable for any
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* special, indirect or consequential damages or any damages
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* whatsoever resulting from loss of use, data or profits, whether
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* in an action of contract, negligence or other tortious action,
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* arising out of or in connection with the use or performance of
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* this software.
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*/
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#include <sys/ioctl.h>
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#include <sys/gpanel.h>
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/*
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* Swap values of two integer variables.
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*/
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#define swapi(x,y) { int _t = x; x = y; y = _t; }
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void gpanel_fill_triangle(int color, int x0, int y0,
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int x1, int y1, int x2, int y2)
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{
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int a, b, y, last;
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// Sort coordinates by Y order (y2 >= y1 >= y0)
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if (y0 > y1) {
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swapi(y0, y1);
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swapi(x0, x1);
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}
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if (y1 > y2) {
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swapi(y2, y1);
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swapi(x2, x1);
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}
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if (y0 > y1) {
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swapi(y0, y1);
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swapi(x0, x1);
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}
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if (y0 == y2) {
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// Handle awkward all-on-same-line case as its own thing
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a = b = x0;
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if (x1 < a)
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a = x1;
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else if (x1 > b)
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b = x1;
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if (x2 < a)
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a = x2;
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else if (x2 > b)
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b = x2;
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gpanel_fill(color, a, y0, b-a+1, y0);
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return;
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}
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int dx01 = x1 - x0;
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int dy01 = y1 - y0;
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int dx02 = x2 - x0;
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int dy02 = y2 - y0;
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int dx12 = x2 - x1;
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int dy12 = y2 - y1;
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int sa = 0;
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int sb = 0;
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// For upper part of triangle, find scanline crossings for segments
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// 0-1 and 0-2. If y1=y2 (flat-bottomed triangle), the scanline y1
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// is included here (and second loop will be skipped, avoiding a /0
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// error there), otherwise scanline y1 is skipped here and handled
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// in the second loop...which also avoids a /0 error here if y0=y1
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// (flat-topped triangle).
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if (y1 == y2)
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last = y1; // Include y1 scanline
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else
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last = y1-1; // Skip it
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for (y=y0; y<=last; y++) {
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a = x0 + sa / dy01;
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b = x0 + sb / dy02;
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sa += dx01;
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sb += dx02;
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/* longhand:
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* a = x0 + (x1 - x0) * (y - y0) / (y1 - y0);
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* b = x0 + (x2 - x0) * (y - y0) / (y2 - y0);
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*/
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if (a > b)
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swapi(a, b);
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gpanel_fill(color, a, y, b-a+1, y);
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}
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// For lower part of triangle, find scanline crossings for segments
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// 0-2 and 1-2. This loop is skipped if y1=y2.
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sa = dx12 * (y - y1);
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sb = dx02 * (y - y0);
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for (; y<=y2; y++) {
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a = x1 + sa / dy12;
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b = x0 + sb / dy02;
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sa += dx12;
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sb += dx02;
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/* longhand:
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* a = x1 + (x2 - x1) * (y - y1) / (y2 - y1);
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* b = x0 + (x2 - x0) * (y - y0) / (y2 - y0);
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*/
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if (a > b)
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swapi(a, b);
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gpanel_fill(color, a, y, b-a+1, y);
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}
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}
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