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The gradient is a fancy word for derivative, or the rate of change of a function. Itâs a vector (a direction to move) that. 1  Points in the direction of greatest increase of a function (intuition on why)  Is zero at a local maximum or local minimum (because there is no single direction of increase)
The magnitude of the gradient tells us how quickly the image is changing, while the direction of the gradient tells us the direction in which the image is changing most rapidly. To illustrate this, think of an image as like a terrain, in which at each point we are given a height, rather than an intensity.e will see that the gradient allows us to answer this question. Letâs consider how the image changes as we move from position (x,y) by a small amount, â, in an arbitrary direction Î¸, which will take us to the position (x+ â cos Î¸, y + â sin Î¸). At (x,y) the image intensity is I(x,y) .