Description:
------------
in gd_topal.c in function pass2_no_dither line 1321

transparency detection code, the pointer is off by one causing a nontransparent band in the transparent region in the resulting picture.

The inptr pointer has already been incremented to the next pixel at the transparency check. should be changed to (inptr-1) to check the correct pixel.

Reproduce code:
---------------
bad code:
	  r = gdTrueColorGetRed (*inptr);
	  g = gdTrueColorGetGreen (*inptr);
	  b = gdTrueColorGetBlue (*inptr++);

	  /* If the pixel is transparent, we assign it the palette index that
	   * will later be added at the end of the palette as the transparent
	   * index. */
	  if ((im->transparent >= 0) && (im->transparent == *inptr))
	    {
	      *outptr++ = im->colorsTotal;
	      continue;
	    }

Expected result:
----------------
*** gd_topal_original.c 2004-05-07 18:26:49.000000000 +0800
--- gd_topal.c  2004-05-07 17:30:29.000000000 +0800
***************
*** 1318,1324 ****
          /* If the pixel is transparent, we assign it the palette index that
           * will later be added at the end of the palette as the transparent
           * index. */
!         if ((im->transparent >= 0) && (im->transparent == *inptr))
            {
              *outptr++ = im->colorsTotal;
              continue;
--- 1318,1324 ----
          /* If the pixel is transparent, we assign it the palette index that
           * will later be added at the end of the palette as the transparent
           * index. */
!         if ((im->transparent >= 0) && (im->transparent == *(inptr-1)))
            {
              *outptr++ = im->colorsTotal;
              continue;

Actual result:
--------------
a bad picture.