rsvd (version 2.0.0)

tiger: Tiger image

Description

A grayscale tiger photograph for examining how low-rank approximation changes image detail. The image is stored as a matrix, so a factorization and its reconstruction can be compared directly with the original pixels. Intensities have been divided by 255 to lie between zero and one.

Usage

data("tiger")

Format

A numeric matrix with 1600 rows and 1200 columns. There are no labels or color channels; each entry is a grayscale intensity.

Details

The stored orientation is suitable for image as shown below. Matrix rows and columns correspond to the horizontal and vertical axes used by that function, respectively. For a decomposition, use tiger directly and reconstruct the matrix in the same orientation.

The photograph is not exactly low rank. A low-rank factorization retains part of its structure, and increasing the approximation rank preserves more texture and fine detail. Storing only the factors can require much less space than storing all pixels. See rsvd, rid and rcur for decomposition examples.

References

S. Taheri (2006), edited by Fir0002. Panthera tigris altaica. Online photograph, distributed under Creative Commons Attribution-ShareAlike 2.5. The package supplies a grayscale conversion.

Examples

data("tiger")
dim(tiger)
range(tiger)
image(seq_len(nrow(tiger)), seq_len(ncol(tiger)), tiger,
      col = gray((0:255) / 255), asp = 1,
      axes = FALSE, useRaster = TRUE)