PK M - Peak search - Maximum

(1/22/16)

PURPOSE

Searches for maximum peak in an image. Reports average location for peak in case there are multiple maxima, thus it handles plateaus better than 'PK'   Example.

SEE ALSO

PK [Peak search]
PK D [Peak search - output to Document file]
PK DR [Peak search - Restricted neighborhood, output to Document file]
PK 3 [Peak search - 3D]

USAGE

.OPERATION: PK M [xii],[yii], [xo],[yo], [pk],[nmax],[bsize]
[This operation can return up to seven optional register variables:
Variable Example Receives
First [xii] X location of max relative to image
Second [yii] Y location of max relative to image
Third [xo] X location of max relative to origin
Fourth [yo] Y location of max relative to origin
Fifth [pk] Peak height (maximum)
Sixth [nmax] Number of maximal pixels
Seventh [bsize] Peak bounding box radius

.INPUT FILE: IMG001
[Enter the name of the image file.]

.ENTER ORIGIN COORDINATES OR <CR> FOR CENTER: 1, 1
[Enter the origin coordinates for reporting sub-pixel locations. If you desire results relative to upper left image corner you should use 1,1 since SPIDER images start with position 1,1 .]

[In the above example, the computer will find the highest peak. Its position will be printed in the RESULTS file. The register variables can be used as input to a subsequent shift ('SH') operation.

NOTES

  1. This operation finds the average "maximum" location when an image has plateaus. Operation: 'PK' does not report this location. Note that the average location may not have a maximal value . If there are multiple plateaus at the maximal value then the location results may be non-intuitive.

  2. If there is only a single maximal pixel the coordinates are adjusted using a parabolic surface to give sub-pixel accuracy.

  3. The bounding box radius is the maximal radius of a bounding box containing all maximal pixels. This radius is zero if there is only a single maximal pixel.

  4. Maxima occurring on the boundary of the image are included in the calculation.

  5. The RESULTS file contains output as follows:
    NMAX X Y XO YO HEIGHT RADIUS
    NMAX Number of maximum value pixels
    X X peak location relative to image
    Y Y peak location relative to image
    XO X peak location relative to origin
    YO Y peak location relative to origin
    HEIGHT Peak height
    RADIUS Peak bounding box radius

SUBROUTINES

SPEAKM

CALLER

UTIL1

© Copyright Notice /       Enquiries: spider@wadsworth.org