Source code for Xiaolin Wu's line algorithm in C?

Question

I'm looking for a nice and efficient implementation of Xiaolin Wu's anti-aliased line drawing algorithm in C, does anyone have this code they could share with me?

Thanks

score 13 · Accepted Answer · edited Jun 08 '16 at 14:24

13

Wikipedia has pseudo code.

Google has many examples like this one or this one. And your question reminded me this nice article on antialiasing.

EDIT: It's time to discover Hugo Helias's website if you don't know it already.

edited Jun 08 '16 at 14:24

genpfault

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answered Dec 14 '09 at 15:01

Gregory Pakosz

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thanks the second link was exactly what i wanted. I searched on google myself but for some reason couldn't get these links, thanks! :) – horseyguy Dec 14 '09 at 15:42
The Wikipedia pseudocode doesn't work if the line end is to the left or above the line start (IOW it only works increasing X,Y) – smirkingman Dec 09 '19 at 11:57

Sadderdaze · Answer 2 · 2019-04-11T08:56:17.687

Wondering if implementation here is correct, because in

ErrorAdj = ((unsigned long) DeltaX << 16) / (unsigned long) DeltaY;
      /* Draw all pixels other than the first and last */
while (--DeltaY) {
         ErrorAccTemp = ErrorAcc;   /* remember current accumulated error */
         ErrorAcc += ErrorAdj;      /* calculate error for next pixel */
         if (ErrorAcc <= ErrorAccTemp) {
            /* The error accumulator turned over, so advance the X coord */
            X0 += XDir;
         }
         Y0++; /* Y-major, so always advance Y */
         /* The IntensityBits most significant bits of ErrorAcc give us the
            intensity weighting for this pixel, and the complement of the
            weighting for the paired pixel */
         Weighting = ErrorAcc >> IntensityShift;
         DrawPixel(pDC,X0, Y0, BaseColor + Weighting);
         DrawPixel(pDC,X0 + XDir, Y0,
               BaseColor + (Weighting ^ WeightingComplementMask));
      }

condition if (ErrorAcc <= ErrorAccTemp) is always false.

Source code for Xiaolin Wu's line algorithm in C?

2 Answers2