write.image {adimpro}

I/O Functions

Description

Write an image file.

Usage

write.image(img, file = "tmp.ppm", max.x=NULL, max.y=NULL, depth = NULL, gammatype="ITU", 
        whitep = NULL, temp = NULL, cspace = NULL, black = 0, exposure = 1)

Arguments

img

image data, an object of class "adimpro".

file

file name, the extension determines the image file format.

max.x

maximum value of pixels in x dimension.

max.y

maximum value of pixels in y dimension.

depth

color depth, either 8 or 16 (bit)! The value is reset to 8 if the specified image file format does not allow for 16 Bit encoding.

gammatype

character, determines the type of gamma correction within the image. "ITU" stands for ITU-R BT.709-3 as e.g. used by dcraw. Alternatives recognized within the package are "None", "sRGB" and "CIE" (CIE L*). NULL keeps the actual setting. gammatype="histogram" forces histogram equalization based on the corresponding greyvalue image.

cspace

defines the output color space, default is img$cspace can be set to "sRGB", "Adobe" (Adobe 1998), "wGamut" (Wide Gamut), "kodak" (Kodak ProPhoto) "xyz", "yuv", "yiq" and "hsi"

whitep

White point in xyY space. Can be given as one of (character) c("A","B","C","E","D50","D55","D65","D75","F2","F7","F11") or as a two element numeric vector of chromatic xy coordinates. "D65" corresponds to the default white point of "sRGB" and "Adobe" RGB-spaces. NULL keeps the actual setting.

temp

Color temperature. Can be used to specify chromatic xy coordinates of the whitepoint. Only used if is.null(whitep).

black

Adjustment for black color. Color values with luminance <= black will be assigned to black in RGB. Adjustment ist done in xyY space.

exposure

Multiplicative factor for all color channels (in xyz or rgb spaces). Applied in linear color space, i.e. if the image is gamma corrected the gamma correction is reversed first.

Details

This function writes the image data in img to the file file. Color depth depth is used for writing, but if image has a component "depth", this argument will be ignored. Note: Not all target formats support 16bit coding. The target format is determined from the file extension, and should be one of the many that ImageMagick supports.

Note that write image by default applies a gamma correction with gammatype="ITU". This provides a good standard for display on a screen. For printing cspace="Adobe" should be prefered. Images that are intended for further editing should preferably be saved in an image format that allows for 16Bit depth (tiff, png) using either cspace="Adobe", cspace="wGamut" or cspace="kodak" and preferably no gamma correction to prevent from additional loss of information.

Value

Nothing is returned.

Note

ImageMagick has to be installed on the system to write "tif", "tiff", "png", "gif", "jpg" or "jpeg" files.

Author(s)

Karsten Tabelow [e-mail] and Joerg Polzehl [e-mail]

See Also

read.image, adjust.image

Examples

## Not run: demo(io)