#28304 [Asn]: ImageFilter, no bounds check processing image per-pixel: creates a black border
ID: 28304
Updated by: pajoye@php.net
Reported By: ken at sonicwizardry dot com
Status: Assigned
Bug Type: GD related
Operating System: Linux
PHP Version: 5.0.0RC2
Assigned To: pajoye
New Comment:
the patch is ok, however I prefer to do the check only once outside the
loops.
Let me check first if it's possible for this filter. Which one are
using?
Pierre
Previous Comments:
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[2004-05-06 18:50:38] ken at sonicwizardry dot com
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.
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