pixmap (version 0.1-2)

pixmap: Pixmap Images

Description

The family "pixmap" (``pixel maps'') of classes provides methods for creating, plotting and converting bitmapped images in three different formats: RGB, grey and indexed pixmaps.

Usage

pixmap(data=0, nrow=1, ncol=1, col=NULL,
       type=c("grey","rgb","indexed"), bbox=NULL)
as.pixmapRGB(object)
as.pixmapGrey(object, coefs=c(0.30, 0.59, 0.11))
as.pixmapIndexed(object)
## S3 method for class 'pixmap':
plot(x, ...)

Arguments

data

An optional data vector.

nrow

Vertical size of the image in pixels.

ncol

Horizontal size of the image in pixels.

col

Character vector of colors to use if type is "indexed".

type

Type of pixmap to create, see details below.

bbox

Bounding box of the image, vector of length 4 of form c(x1, y1, x2, y2) with coordinates for the lower left corner and upper right corner.

x, object

Object of class "pixmap"

coefs

Coefficients used for converting a color image to grey. The grey value is simply the weighted sum of the channels red, green and blue in each pixel.

...

Graphical parameters passed to image.

Details

Class "pixmap" has currently the three subclasses "pixmapRGB", "pixmapGrey", and "pixmapIndexed". The optional bounding box specifies a coordinate system for the image and is, e.g., used for labelling the axes in plots. Methods for coercion between all formats are available.

RGB pixmaps are three-dimensional arrays where the first two dimensions give the size of the image in pixels and the third dimension is for the three color channels red, green and blue. Elements of the array must be between 0 (=color off) and 1 (=color at maximum).

Grey and indexed pixmaps are matrices, the element [1,1] corresponds to the upper left corner as usual. For grey pixmaps the elements must be between 0 (black) and 1 (white). Indexed pixmaps have integer elements, each giving the index number corresponding to the palette specified in "col". Colors are given using the usual R color strings (either names like "red" or hex values like "#FF0000").

The name pixmap was chosen because both image and bitmap are already used in R.

See Also

read.pnm

Examples

x <- pixmap(rep(1:8, 9), nrow=6, col=rainbow(8), type="indexed")
 plot(x)
 plot(x, asp=.5)
 plot(as.pixmapGrey(x))

 x <- read.pnm(system.file("pictures/logo.ppm", package="pixmap")[1])
 plot(x)

 x <- seq(-3,3,length=100)
 z1 <- outer(x,x,function(x,y) abs(sin(x)*sin(y)))
 z2 <- outer(x,x,function(x,y) abs(sin(2*x)*sin(y)))
 z3 <- outer(x,x,function(x,y) abs(sin(x)*sin(2*y)))
 z <- pixmap(c(z1,z2,z3), 100, 100, type="rgb", bbox=c(-1,-1,1,1))
 plot(z, axes=TRUE)