u8g_line.c

00001 /*
00002 
00003   u8g_line.h
00004   
00005   Universal 8bit Graphics Library
00006   
00007   Copyright (c) 2012, olikraus@gmail.com
00008   All rights reserved.
00009 
00010   Redistribution and use in source and binary forms, with or without modification, 
00011   are permitted provided that the following conditions are met:
00012 
00013   * Redistributions of source code must retain the above copyright notice, this list 
00014     of conditions and the following disclaimer.
00015     
00016   * Redistributions in binary form must reproduce the above copyright notice, this 
00017     list of conditions and the following disclaimer in the documentation and/or other 
00018     materials provided with the distribution.
00019 
00020   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
00021   CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
00022   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
00023   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
00024   DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
00025   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
00026   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
00027   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
00028   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
00029   CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
00030   STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
00031   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
00032   ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
00033   
00034 */
00035 
00036 #include "u8g.h"
00037 
00038 void u8g_DrawLine(u8g_t *u8g, u8g_uint_t x1, u8g_uint_t y1, u8g_uint_t x2, u8g_uint_t y2)
00039 {
00040   u8g_uint_t tmp;
00041   u8g_uint_t x,y;
00042   u8g_uint_t dx, dy;
00043   u8g_int_t err;
00044   u8g_int_t ystep;
00045 
00046   uint8_t swapxy = 0;
00047   
00048   /* no BBX intersection check at the moment, should be added... */
00049 
00050   if ( x1 > x2 ) dx = x1-x2; else dx = x2-x1;
00051   if ( y1 > y2 ) dy = y1-y2; else dy = y2-y1;
00052 
00053   if ( dy > dx ) 
00054   {
00055     swapxy = 1;
00056     tmp = dx; dx =dy; dy = tmp;
00057     tmp = x1; x1 =y1; y1 = tmp;
00058     tmp = x2; x2 =y2; y2 = tmp;
00059   }
00060   if ( x1 > x2 ) 
00061   {
00062     tmp = x1; x1 =x2; x2 = tmp;
00063     tmp = y1; y1 =y2; y2 = tmp;
00064   }
00065   err = dx >> 1;
00066   if ( y2 > y1 ) ystep = 1; else ystep = -1;
00067   y = y1;
00068   for( x = x1; x <= x2; x++ )
00069   {
00070     if ( swapxy == 0 ) 
00071       u8g_DrawPixel(u8g, x, y); 
00072     else 
00073       u8g_DrawPixel(u8g, y, x); 
00074     err -= (uint8_t)dy;
00075     if ( err < 0 ) 
00076     {
00077       y += (u8g_uint_t)ystep;
00078       err += (u8g_uint_t)dx;
00079     }
00080   }
00081 }
00082