Bresenham is an algorithm for devices that only have 1 bit pixels, on and off. You also get very nasty artifacts. A line from (0, 0) to (8, 2) would look like: 
    +-+-+-+-+-+-+-+-+-+
    | | | | | | |*|*|*|
    +-+-+-+-+-+-+-+-+-+
    | | | |*|*|*| | | |
    +-+-+-+-+-+-+-+-+-+
    |*|*|*| | | | | | | 
    +-+-+-+-+-+-+-+-+-+

[download]

Now, if all your pixels are either black or white, this isn't too bad. But the human eye is very good in seeing the non-smoothness, the "staircase" sticks out like a sore thumb.

But if you have a grayscale (or full colour) device available, there are much better techniques. One technique revolves around the observation a line needs thickness to be seen. So, if you want to draw a line from say (0, 0) to (8, 2), assume you have a rectangle of width 1 and length 2 * sqrt (17), running from (0, 0) to (8, 2). This will cover some of the pixels partially. If a pixel is covered for say, 61%, the pixel should get a gray value that's 61% of pure black.

Now, this still isn't perfect, but it's a step better. There are lots of line drawing algorithms, each of them finding a different balance between simplicity, speed, good results and avoidance of artifacts.

Abigail

In reply to Re: Plotting A Line by Abigail-II
in thread Plotting A Line by mdog

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