Diagonal line for GLCD - Electronic Circuits Projects Diagrams Free

superbrew · 30th March 2008, 03:32 AM

Hello again, i am trying to write a function to draw a line from (x1,y1) to (x2,y2) on a GLCD. What I have so far only works if the slope of the line is 1 and x1,y1 values are less than x2,y2 values. Please be patient with me, lol.

Code:

void dline(unsigned char x1, unsigned char x2,unsigned char y1,unsigned char y2){
	signed int dx,dy;
	double slope,draw;
	
	//plot start
	plot(x1,y1);
	//find delta and delta y
	dx=(x2-x1);
	dy=(y2-y1);
	//find slope
	slope = dx/dy;
	//draw the line
	while(dx--){
		for(draw=0;draw<=(slope-1);draw++)
		{
			plot(x1,y1);
			y1++;			
		}
		x1++;		
	}
}

futz · 30th March 2008, 03:38 AM

Google for Bresenham's algorithm. Even looking for just the basic one should get you a version that will handle any angle, and drawing from either end.

Then start digging for all the improved versions that have been made. The improved ones are MUCH faster.

Pommie · 30th March 2008, 03:50 AM

I have a line draw in asm if that's any use.

Mike.

futz · 30th March 2008, 03:55 AM

If you can, get yourself a copy of this old book. I see there's some used copies available for cheap on Amazon. It goes over all the very basic graphic algo's in pretty good detail, progressing to improved versions as you learn how the simpler ones work. I bought it when it was new, for MUCH, MUCH more than you're going to pay.

superbrew · 30th March 2008, 09:25 PM

Thanks for the replies. It looks like I have a lot more reading to do. For some reason, it does not seem like there is a lot of info on the net regarding glcd's and pics.

futz · 30th March 2008, 09:37 PM

Quote:

Originally Posted by superbrew

Thanks for the replies. It looks like I have a lot more reading to do. For some reason, it does not seem like there is a lot of info on the net regarding glcd's and pics.

There isn't much out there, which is why I'm posting my reckless adventures online. But graphic algorithms are the same whether your screen is 128x64 or 1680x1050.

**Nigel Goodwin** · 30th March 2008, 11:33 PM

I've got an old book somewhere, in 6502 assembler, which gave routines for all kinds of text and graphic manipulation - there are probably various old books from back then.

futz · 31st March 2008, 07:09 AM

Quote:

Originally Posted by superbrew

Hello again, i am trying to write a function to draw a line from (x1,y1) to (x2,y2) on a GLCD. What I have so far only works if the slope of the line is 1 and x1,y1 values are less than x2,y2 values. Please be patient with me, lol.

Hey superbrew. If you don't mind cheating, I borrowed and ported to C a piece of BlitzMax BASIC code I borrowed off the interweb. It works perfect on my GLCD. Just now got the last buglets out of it. It's pretty quick. All integers. If you want it, just say so.

watzmann · 31st March 2008, 08:02 AM

i have wrote my code using Microbasic , if it can help i'll send to you .

it works very well ,

even i have wrote code for the eraser !

futz · 31st March 2008, 08:06 AM

Quote:

Originally Posted by watzmann

even i have wrote code for the eraser !

What is "the eraser"?

I'm just now posting an update on my site. Some new movies of simple glcd animation demos and a picture. Should be up in 10 or 15 minutes.

Pommie · 31st March 2008, 08:11 AM

That would be drawing in colour zero on a background of zero. :-)

Mike.

futz · 31st March 2008, 08:13 AM

Quote:

Originally Posted by Pommie

That would be drawing in colour zero on a background of zero. :-)

Heh

LOL

watzmann · 31st March 2008, 01:36 PM

loll . for you eraser means when you draw a line and need to select it and erase .

exaclty like what happens with CAD softwares , draw aline , or a circle , and if you don't like it you can remove .

try to do it :P

superbrew · 31st March 2008, 02:01 PM

Thanks guys for the offers. I don't actually need this code, I am just trying to learn how do some stuff with a GLCD. MikroC has some nice functions for drawing lines and circles, but you don't have access to how they do it. I think from the information given I should be able to fiure it out.

futz · 31st March 2008, 03:32 PM

Quote:

Originally Posted by watzmann

loll . for you eraser means when you draw a line and need to select it and erase .

exaclty like what happens with CAD softwares , draw aline , or a circle , and if you don't like it you can remove .

try to do it :P

Easy. Just XOR the same bits again. See the animation movies on my site. It's not clearing the screen between moves (though that might be quicker

). It's erasing (redrawing in background color) the line just before drawing the new one.

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30th March 2008, 03:38 AM	(permalink)
futz	Google for Bresenham's algorithm. Even looking for just the basic one should get you a version that will handle any angle, and drawing from either end. Then start digging for all the improved versions that have been made. The improved ones are MUCH faster. __________________ ========================= Futz's Microcontrollers & Robotics =========================

30th March 2008, 03:50 AM	(permalink)
Pommie	I have a line draw in asm if that's any use. Mike.

30th March 2008, 03:55 AM	(permalink)
futz	If you can, get yourself a copy of this old book. I see there's some used copies available for cheap on Amazon. It goes over all the very basic graphic algo's in pretty good detail, progressing to improved versions as you learn how the simpler ones work. I bought it when it was new, for MUCH, MUCH more than you're going to pay. __________________ ========================= Futz's Microcontrollers & Robotics =========================

30th March 2008, 09:25 PM	(permalink)
superbrew	Thanks for the replies. It looks like I have a lot more reading to do. For some reason, it does not seem like there is a lot of info on the net regarding glcd's and pics.

30th March 2008, 11:33 PM	(permalink)
Nigel Goodwin	I've got an old book somewhere, in 6502 assembler, which gave routines for all kinds of text and graphic manipulation - there are probably various old books from back then. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

31st March 2008, 08:02 AM	(permalink)
watzmann	i have wrote my code using Microbasic , if it can help i'll send to you . it works very well , even i have wrote code for the eraser !

31st March 2008, 08:11 AM	(permalink)
Pommie	That would be drawing in colour zero on a background of zero. :-) Mike.

31st March 2008, 01:36 PM	(permalink)
watzmann	loll . for you eraser means when you draw a line and need to select it and erase . exaclty like what happens with CAD softwares , draw aline , or a circle , and if you don't like it you can remove . try to do it :P

31st March 2008, 02:01 PM	(permalink)
superbrew	Thanks guys for the offers. I don't actually need this code, I am just trying to learn how do some stuff with a GLCD. MikroC has some nice functions for drawing lines and circles, but you don't have access to how they do it. I think from the information given I should be able to fiure it out.