Method
VipsImagespcor
Declaration [src]
int
vips_spcor (
VipsImage* in,
VipsImage* ref,
VipsImage** out,
...
)
Description [src]
Calculate a correlation surface.
ref is placed at every position in in and the correlation coefficient
calculated. The output
image is always float.
The output image is the same size as the input. Extra input edge pixels are made by copying the existing edges outwards.
The correlation coefficient is calculated as:
sumij (ref(i,j)-mean(ref))(inkl(i,j)-mean(inkl))
c(k,l) = ------------------------------------------------
sqrt(sumij (ref(i,j)-mean(ref))^2) *
sqrt(sumij (inkl(i,j)-mean(inkl))^2)
where inkl is the area of in centred at position (k,l).
from Niblack “An Introduction to Digital Image Processing”, Prentice/Hall, pp 138.
If the number of bands differs, one of the images must have one band. In this case, an n-band image is formed from the one-band image by joining n copies of the one-band image together, and then the two n-band images are operated upon.
The output image is always float, unless either of the two inputs is double, in which case the output is also double.
See also: vips_fastcor().
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