335 lines
7.8 KiB
C
335 lines
7.8 KiB
C
/*
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u8g_polygon.c
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Implementation of a polygon draw algorithm for "convex" polygons.
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Universal 8bit Graphics Library
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Copyright (c) 2013, olikraus@gmail.com
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or other
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materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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See also:
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http://www.angelfire.com/linux/myp/ConvexPolRas/ConvexPolRas.html
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Computer Graphics, Principles and Practice, Foley, van Dam, Feiner, Hughes (pp 92)
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Michael Abrash's Graphics Programming Black Book, Special Edition (Chapter 38 and 39)
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Optimized for embedded systems
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- static memory usage only
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- consistent data types
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- low flash ROM consumption
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*/
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#include "u8g.h"
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/*===========================================*/
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/* procedures, which should not be inlined (save as much flash ROM as possible */
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static uint8_t pge_Next(struct pg_edge_struct *pge) PG_NOINLINE;
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static uint8_t pg_inc(pg_struct *pg, uint8_t i) PG_NOINLINE;
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static uint8_t pg_dec(pg_struct *pg, uint8_t i) PG_NOINLINE;
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static void pg_expand_min_y(pg_struct *pg, pg_word_t min_y, uint8_t pge_idx) PG_NOINLINE;
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static void pg_line_init(pg_struct * const pg, uint8_t pge_index) PG_NOINLINE;
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/*===========================================*/
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/* line draw algorithm */
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static uint8_t pge_Next(struct pg_edge_struct *pge)
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{
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if ( pge->current_y >= pge->max_y )
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return 0;
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pge->current_x += pge->current_x_offset;
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pge->error += pge->error_offset;
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if ( pge->error > 0 )
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{
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pge->current_x += pge->x_direction;
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pge->error -= pge->height;
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}
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pge->current_y++;
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return 1;
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}
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/* assumes y2 > y1 */
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static void pge_Init(struct pg_edge_struct *pge, pg_word_t x1, pg_word_t y1, pg_word_t x2, pg_word_t y2)
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{
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pg_word_t dx = x2 - x1;
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pg_word_t width;
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pge->height = y2 - y1;
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pge->max_y = y2;
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pge->current_y = y1;
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pge->current_x = x1;
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if ( dx >= 0 )
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{
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pge->x_direction = 1;
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width = dx;
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pge->error = 0;
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}
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else
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{
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pge->x_direction = -1;
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width = -dx;
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pge->error = 1 - pge->height;
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}
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pge->current_x_offset = dx / pge->height;
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pge->error_offset = width % pge->height;
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}
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/*===========================================*/
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/* convex polygon algorithm */
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static uint8_t pg_inc(pg_struct *pg, uint8_t i)
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{
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i++;
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if ( i >= pg->cnt )
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i = 0;
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return i;
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}
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static uint8_t pg_dec(pg_struct *pg, uint8_t i)
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{
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i--;
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if ( i >= pg->cnt )
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i = pg->cnt-1;
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return i;
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}
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static void pg_expand_min_y(pg_struct *pg, pg_word_t min_y, uint8_t pge_idx)
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{
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uint8_t i = pg->pge[pge_idx].curr_idx;
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for(;;)
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{
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i = pg->pge[pge_idx].next_idx_fn(pg, i);
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if ( pg->list[i].y != min_y )
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break;
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pg->pge[pge_idx].curr_idx = i;
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}
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}
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static uint8_t pg_prepare(pg_struct *pg)
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{
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pg_word_t max_y;
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pg_word_t min_y;
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uint8_t i;
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/* setup the next index procedures */
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pg->pge[PG_RIGHT].next_idx_fn = pg_inc;
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pg->pge[PG_LEFT].next_idx_fn = pg_dec;
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/* search for highest and lowest point */
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max_y = pg->list[0].y;
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min_y = pg->list[0].y;
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pg->pge[PG_LEFT].curr_idx = 0;
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for( i = 1; i < pg->cnt; i++ )
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{
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if ( max_y < pg->list[i].y )
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{
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max_y = pg->list[i].y;
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}
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if ( min_y > pg->list[i].y )
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{
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pg->pge[PG_LEFT].curr_idx = i;
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min_y = pg->list[i].y;
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}
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}
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/* calculate total number of scan lines */
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pg->total_scan_line_cnt = max_y;
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pg->total_scan_line_cnt -= min_y;
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/* exit if polygon height is zero */
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if ( pg->total_scan_line_cnt == 0 )
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return 0;
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/* if the minimum y side is flat, try to find the lowest and highest x points */
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pg->pge[PG_RIGHT].curr_idx = pg->pge[PG_LEFT].curr_idx;
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pg_expand_min_y(pg, min_y, PG_RIGHT);
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pg_expand_min_y(pg, min_y, PG_LEFT);
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/* check if the min side is really flat (depends on the x values) */
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pg->is_min_y_not_flat = 1;
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if ( pg->list[pg->pge[PG_LEFT].curr_idx].x != pg->list[pg->pge[PG_RIGHT].curr_idx].x )
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{
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pg->is_min_y_not_flat = 0;
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}
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else
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{
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pg->total_scan_line_cnt--;
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if ( pg->total_scan_line_cnt == 0 )
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return 0;
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}
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return 1;
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}
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static void pg_hline(pg_struct *pg, u8g_t *u8g)
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{
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pg_word_t x1, x2, y;
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x1 = pg->pge[PG_LEFT].current_x;
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x2 = pg->pge[PG_RIGHT].current_x;
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y = pg->pge[PG_RIGHT].current_y;
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if ( y < 0 )
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return;
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if ( y >= u8g_GetHeight(u8g) )
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return;
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if ( x1 < x2 )
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{
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if ( x2 < 0 )
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return;
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if ( x1 >= u8g_GetWidth(u8g) )
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return;
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if ( x1 < 0 )
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x1 = 0;
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if ( x2 >= u8g_GetWidth(u8g) )
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x2 = u8g_GetWidth(u8g);
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u8g_DrawHLine(u8g, x1, y, x2 - x1);
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}
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else
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{
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if ( x1 < 0 )
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return;
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if ( x2 >= u8g_GetWidth(u8g) )
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return;
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if ( x2 < 0 )
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x1 = 0;
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if ( x1 >= u8g_GetWidth(u8g) )
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x1 = u8g_GetWidth(u8g);
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u8g_DrawHLine(u8g, x2, y, x1 - x2);
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}
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}
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static void pg_line_init(pg_struct * pg, uint8_t pge_index)
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{
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struct pg_edge_struct *pge = pg->pge+pge_index;
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uint8_t idx;
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pg_word_t x1;
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pg_word_t y1;
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pg_word_t x2;
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pg_word_t y2;
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idx = pge->curr_idx;
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y1 = pg->list[idx].y;
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x1 = pg->list[idx].x;
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idx = pge->next_idx_fn(pg, idx);
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y2 = pg->list[idx].y;
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x2 = pg->list[idx].x;
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pge->curr_idx = idx;
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pge_Init(pge, x1, y1, x2, y2);
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}
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static void pg_exec(pg_struct *pg, u8g_t *u8g)
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{
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pg_word_t i = pg->total_scan_line_cnt;
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/* first line is skipped if the min y line is not flat */
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pg_line_init(pg, PG_LEFT);
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pg_line_init(pg, PG_RIGHT);
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if ( pg->is_min_y_not_flat != 0 )
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{
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pge_Next(&(pg->pge[PG_LEFT]));
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pge_Next(&(pg->pge[PG_RIGHT]));
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}
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do
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{
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pg_hline(pg, u8g);
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while ( pge_Next(&(pg->pge[PG_LEFT])) == 0 )
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{
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pg_line_init(pg, PG_LEFT);
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}
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while ( pge_Next(&(pg->pge[PG_RIGHT])) == 0 )
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{
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pg_line_init(pg, PG_RIGHT);
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}
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i--;
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} while( i > 0 );
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}
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/*===========================================*/
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/* API procedures */
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void pg_ClearPolygonXY(pg_struct *pg)
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{
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pg->cnt = 0;
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}
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void pg_AddPolygonXY(pg_struct *pg, u8g_t *u8g, int16_t x, int16_t y)
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{
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if ( pg->cnt < PG_MAX_POINTS )
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{
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pg->list[pg->cnt].x = x;
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pg->list[pg->cnt].y = y;
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pg->cnt++;
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}
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}
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void pg_DrawPolygon(pg_struct *pg, u8g_t *u8g)
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{
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if ( pg_prepare(pg) == 0 )
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return;
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pg_exec(pg, u8g);
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}
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pg_struct u8g_pg;
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void u8g_ClearPolygonXY(void)
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{
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pg_ClearPolygonXY(&u8g_pg);
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}
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void u8g_AddPolygonXY(u8g_t *u8g, int16_t x, int16_t y)
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{
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pg_AddPolygonXY(&u8g_pg, u8g, x, y);
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}
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void u8g_DrawPolygon(u8g_t *u8g)
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{
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pg_DrawPolygon(&u8g_pg, u8g);
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}
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void u8g_DrawTriangle(u8g_t *u8g, int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2, int16_t y2)
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{
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u8g_ClearPolygonXY();
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u8g_AddPolygonXY(u8g, x0, y0);
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u8g_AddPolygonXY(u8g, x1, y1);
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u8g_AddPolygonXY(u8g, x2, y2);
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u8g_DrawPolygon(u8g);
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}
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