PixelValuePositions

PixelValuePositions[image,val]

returns a list of pixel positions in image that exactly match the value val.

PixelValuePositions[image,val,d]

returns all pixel positions that have values within a distance d from val.

Details

  • PixelValuePositions finds and returns pixels of specific values in 2D and 3D images and is typically used for locating features or removing artifacts.
  • PixelValuePositions assumes a pixel-aligned coordinate system that is shifted by 0.5 to the left and down with respect to the standard image coordinate system.
  • Use ImageValuePositions to get positions in the standard image coordinate system.
  • The pixel value val can be in one of the following forms:
  • sa scalar
    colora color
    {s1,s2,}a list of channel values
    "Max"pixels with maximum intensity
    "Min"pixels with minimum intensity
  • In 3D, PixelValuePositions[image,val] returns the positions {xp,yp,zp}, such that pixel position corresponds to the center of the bottom-left front pixel.

Examples

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Basic Examples  (3)

Extract positions of the white pixels:

Positions of the pixels with values within the specified distance from white:

Positions of white pixels in a 3D image:

Scope  (4)

Positions of the pixels with maximum intensity:

Positions of the pixels with minimum intensity:

Positions of red pixels:

Positions of the pixels with values within the specified distance from red:

Applications  (2)

Extract data coordinates in an image:

Find a best-fit sine function:

Extract coordinates of annotations in a document:

Make the handwritten annotations disappear:

Properties & Relations  (2)

PixelValuePositions[image,val] is equivalent to PixelValuePositions[image,val,0]:

PixelValuePositions[image,val] is equivalent to ImageValuePositions[image,val] plus :

Introduced in 2012
 (9.0)