sobel-operator | js implementation of the sobel operator | Runtime Evironment library

according to wikipedia it's [[1, 0, -1],[2, 0, -2],[1, 0, 1]] but according to other sources it's [[-1, 0, 1],[-2, 0, 2],[-1, 0, 1]]

Both are used for detecting vertical edges. Difference here is how these kernels mark "left" and "right" edges.

For simplicity sake lets consider 1D example, and let array be

[0, 0, 255, 255, 255]

then if we calculate using padding then

• kernel [2, 0, -2] gives [0, -510, -510, 0, 0]
• kernel [-2, 0, 2] gives [0, 510, 510, 0, 0]

As you can see abrupt increase in value was marked with negative values by first kernel and positive values by second. Note that is is relevant only if you need to discriminate left vs right edges, when you want just to find vertical edges, you might use any of these 2 aboves and then get absolute value.