Description:
------------
Running ImageFilter on an image creates a black border around the edge because it references non-existing pixels off of the image (beyond image size).  Bounds check/clamp added to convolution loop.  Code DIFF is below:

File path: ext/gd/libgd/gd.c

3607,3610c3607,3614 

< pxl = f(srcback, x-(3>>1)+i, y-(3>>1)+j); 
< new_r += (float)gdImageRed(srcback, pxl) * filter[j][i]; 
< new_g += (float)gdImageGreen(srcback, pxl) * filter[j][i]; 
< new_b += (float)gdImageBlue(srcback, pxl) * filter[j][i]; 
 
--- 

> int ix = x-(3>>1)+i; 
> int iy = y-(3>>1)+j; 
> ix = (ix>=src->sx)?src->sx-1 : ((ix<0)?0:ix); 
> iy = (iy>=src->sy)?src->sy-1 : ((iy<0)?0:iy); 
> pxl = f(srcback, ix, iy); 
> new_r += (float)gdImageRed(srcback, pxl) * filter[j][i]; 
> new_g += (float)gdImageGreen(srcback, pxl) * filter[j][i]; 
> new_b += (float)gdImageBlue(srcback, pxl) * filter[j][i];


Hope this helps!
-Ken Post Jr.