Return image patch summary
Patches are rectangular image regions centered at cx,cy with width wx and height wy. This function provides a fast way of extracting a statistic over image patches (for example, their mean). Supported functions: sum,mean,min,max,median,var,sd, or any valid CImg expression. WARNINGS: - values outside of the image region are considered to be 0. - widths and heights should be odd integers (they're rounded up otherwise).
patchstat(im, expr, cx, cy, wx, wy)
im |
an image |
expr |
statistic to extract. a string, either one of the usual statistics like "mean","median", or a CImg expression. |
cx |
vector of x coordinates for patch centers |
cy |
vector of y coordinates for patch centers |
wx |
vector of patch widths (or single value) |
wy |
vector of patch heights (or single value) |
a numeric vector
extract_patches
im <- grayscale(boats) #Mean of an image patch centered at (10,10) of size 3x3 patchstat(im,'mean',10,10,3,3) #Mean of image patches centered at (10,10) and (20,4) of size 2x2 patchstat(im,'mean',c(10,20),c(10,4),5,5) #Sample 10 random positions ptch <- pixel.grid(im) %>% dplyr::sample_n(10) #Compute median patch value with(ptch,patchstat(im,'median',x,y,3,3))
Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.