Intensity change after filtering this image? I need to filter the image raster below with the following mask:

 0 1
-1 0


and the Image Raster:

0 0 0 0 0 1
0 0 0 0 1 1
0 0 0 1 1 1
0 0 1 1 1 1
1 1 1 1 1 1


My results are:

 0 0 0 0 0
 0 0 0 0 0
 0 0 0 0 0
-1 0 0 0 0


In what direction does this mask detect intensity change? What does the sign of the output signal mean?
For binary images, the filter kernel you have is looking for a $0 \rightarrow 1$ edge in the North-East direction.  Your image raster only has one place where such an edge exists (in the bottom left / South-West corner).

The sign of the output means that the edge is a $1 \rightarrow 0$ edge transition rather than a $0 \rightarrow 1$ transition.