Non-maximum suppression

最新推荐文章于 2024-08-22 08:21:16 发布

转载最新推荐文章于 2024-08-22 08:21:16 发布 · 1.1k 阅读

数字图像处理专栏收录该内容

72 篇文章

订阅专栏

本文深入探讨了非极大值抑制作为边缘薄化技术在图像处理中的应用，详细解释了如何通过搜索确定图像梯度方向上局部最大值来实现边缘检测。阐述了不同梯度角度下边缘检测的条件，并介绍了更精确实现中线性插值的使用。此外，文章还强调了非极大值抑制技术在确保边缘准确性和减少伪边缘方面的重要性。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Non-maximum suppression is an edge thinning technique.

Given estimates of the image gradients, a search is carried out to determine if the gradient magnitude assumes a local maximum in the gradient direction. In some implementations, the algorithm categorizes the continuous gradient directions into a small set of discrete directions, and then moves a 3x3 filter over the output of the previous step (that is, the edge strength and gradient directions). At every pixel, it suppresses the edge strength of the center pixel (by setting its value to 0) if its magnitude is not greater than the magnitude of the two neighbors in the gradient direction. For example,

if the rounded gradient angle is zero degrees (i.e. the edge is in the north–south direction) the point will be considered to be on the edge if its gradient magnitude is greater than the magnitudes at pixels in the east and west directions,
if the rounded gradient angle is 90 degrees (i.e. the edge is in the east–west direction) the point will be considered to be on the edge if its gradient magnitude is greater than the magnitudes at pixels in the north and south directions,
if the rounded gradient angle is 135 degrees (i.e. the edge is in the northeast–southwest direction) the point will be considered to be on the edge if its gradient magnitude is greater than the magnitudes at pixels in the north west and south east directions,
if the rounded gradient angle is 45 degrees (i.e. the edge is in the north west–south east direction) the point will be considered to be on the edge if its gradient magnitude is greater than the magnitudes at pixels in the north east and south west directions.

In more accurate implementations, linear interpolation is used between the two neighbouring pixels that straddle the gradient direction. For example, if the gradient angle is between 45 degrees and 90 degrees, interpolation between gradients at the north and north east pixels will give one interpolated value, and interpolation between thesouth and south west pixels will give the other (using the conventions of last paragraph). The gradient magnitude at the central pixel must be greater than both of these for it to be marked as an edge.

Note that the sign of the direction is irrelevant, i.e. north–south is the same as south–north and so on.