Image Processing Toolbox User's Guide |

**Distance Transform**

The distance transform provides a metric or measure of the separation of points in the image. The Image Processing Toolbox provides a function, `bwdist`

, that calculates the distance between each pixel that is set to `off`

(`0`

) and the nearest nonzero pixel for binary images.

The `bwdist`

function supports several distance metrics, listed in the following table.

This example creates a binary image containing two intersecting circular objects.

center1 = -10; center2 = -center1; dist = sqrt(2*(2*center1)^2); radius = dist/2 * 1.4; lims = [floor(center1-1.2*radius) ceil(center2+1.2*radius)]; [x,y] = meshgrid(lims(1):lims(2)); bw1 = sqrt((x-center1).^2 + (y-center1).^2) <= radius; bw2 = sqrt((x-center2).^2 + (y-center2).^2) <= radius; bw = bw1 | bw2; figure, imshow(bw), title('bw')

To compute the distance transform of the complement of the binary image, use the `bwdist`

function. In the image of the distance transform, note how the centers of the two circular areas are white.

Finding Peaks and Valleys | Objects, Regions, and Feature Measurement |

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