class Image::Info - Optional method arguments

Table of Contents

instance methods

attribute methods

The Image::Info class

Some Image and ImageList methods, such as read and write, accept an "optional arguments" block in which you can set attributes that modify the method's output. These attributes belong to the Image::Info class. The Image::Info class exists only to accept optional arguments for those Image and ImageList methods.

This page explains the methods defined in the Image::Info class. Generally, each Image or ImageList method that uses the Image::Info class to get optional arguments will only accept some of the attributes listed on this page, that is, only those attributes that are meaningful for the particular method. Any other attributes that you set are ignored. Also, some attributes are only used by a subset of the image formats. See the ImageMagick documentation for more information.

Remember, you do not ever need to create an Image::Info object. The object is created for you before the optional arguments block is entered and destroyed after the block is exited.

All the attributes in the Image::Info class are read/write. For simplicity, and because usually you only set these attributes, just the setter version of each attribute method is described.

instance methods

define

self.define(format, key[, value])

Description

Define a format-specific option. The define method is a new, general-purpose way of specifying options that apply to specific image formats. This method is available in ImageMagick 6.0.0 and GraphicsMagick 1.1.

Arguments

format
An image format name such as "ps" or "tiff".
key
A string that identifies the option.
value
The value of the option. If omitted, the key is simply defined to an null value.

Returns

self

Example

See the ×Magick documentation for the -define utility command option for a list of valid formats, keys, and values.

self.define("tiff", "bits-per-sample", 2)   

Magick API

SetImageOption (ImageMagick 6.0.0), AddDefinitions (GraphicsMagick 1.1)

attribute methods

antialias

self.antialias= true or false

Description

Control antialiasing of rendered Postscript and Postscript or TrueType fonts. The default is true.

background_color

self.background_color= aPixel or aPixel

Description

Set the image background color. The default is "white".

Arguments

A color name or a aPixel.

border_color

self.border_color= aString or aPixel

Description

Set the image border color. The default is "#dfdfdf".

Arguments

A color name or a aPixel.

colorspace

self.colorspace= aColorspaceType

Description

Specify the image pixel interpretation.

Arguments

A ColorspaceType constant.

compression

self.compression= aCompressionType

Description

Specify the image compression type. Not all compression types are supported for all image formats. If you specify an unsupported compression type, the default compression type is used instead.

Arguments

A CompressionType constant.

density

self.density= aString or aGeometry

Description

Specify the vertical and horizontal resolution in pixels. The default density is "72.0x72.0".

Arguments

The argument can be either a string in the form "XxY" where "X" is the horizontal resolution and "Y" is the vertical resolution, or a Geometry object where width is the horizontal resolution and height is the vertical resolution.

depth

self.depth= aNumber

Description

Specify the image depth.

Arguments

Either 8, 16, or 32. You can specify 16 and 32 only when ×Magick was compiled with a QuantumDepth that allows these depth values.

dither

self.dither= true or false

Description

Apply Floyd/Steinberg error diffusion to the image. The basic strategy of dithering is to trade intensity resolution for spatial resolution by averaging the intensities of several neighboring pixels. Images which suffer from severe contouring when reducing colors can be improved with this option.

extract

self.extract= aString or aGeometry

Description

Specify a portion of an image to be extracted when the image is constituted. This attribute can be used to identify a subset of an image that is otherwise too large to keep in memory.

Arguments

Either a geometry string or a Geometry object. For example: self.extract = "200x200+100+100".

Notes

This attribute replaces the tile attribute, which is deprecated in ImageMagick 5.5.6 and later.

filename

self.filename= aString

Description

See capture.

font

self.font= aString

Description

Set the text rendering font.

format

self.format= aString

Description

Set the image format, "GIF" or "JPG" for example.

Arguments

See File Formats.

fuzz

self.fuzz= aNumeric or aString

Description

Set the level of "fuzziness" for comparing pixels. By default the pixels must be identical to be considered equal. The larger the fuzz value the more difference is tolerated.See fuzz.

Arguments

The argument may be a numeric value or a string in the form "NN%". In the second case, the argument is computed as a percentage of MaxRGB. For example, a value of '5%' sets fuzz to 0.05*MaxRGB.

image_type

self.image_type= anImageType

Description

The image type classification. For example, GrayscaleType. Don't confuse this attribute with the format such as "GIF" or "JPG".

Arguments

An ImageType constant.

interlace

self.interlace= anInterlaceType

Description

[S]pecify the type of interlacing scheme for raw image formats such as RGB or YUV. NoInterlace means do not interlace, LineInterlace uses scanline interlacing, and PlaneInterlace uses plane interlacing. PartitionInterlace is like PlaneInterlace except the different planes are saved to individual files (e.g. image.R, image.G, and image.B). Use LineInterlace or PlaneInterlace to create an interlaced GIF or progressive JPEG image. The default is NoInterlace.

Arguments

An InterlaceType constant.

matte_color

self.matte_color= aString or aPixel

Description

Set the image transparent color. The default is "#bdbdbd".

Arguments

A color name or a aPixel.

monochrome

self.monochrome= true or false

Description

Transform the image to black and white on input. Only the ETP, PDF, and PS formats respect this attribute.

number_scenes

self.number_scenes= anInteger

Description

Used in conjunction with scene to specify the range of frames to be extracted when constituting a multi-frame image.

Note

This attribute replaces the subrange attribute, which is deprecated in ImageMagick 5.5.6 and later. If number_scenes is used with a version of ImageMagick prior to 5.5.6, it is a synonym for the subrange attribute.

page

self.page= aString or aGeometry

Description

Set the equivalent size of the Postscript page. The default is "612x792>".

Arguments

A geometry string or a Geometry object.

quality

self.quality= anInteger

Description

Set the compression level to use when writing JPEG, MIFF, and PNG images. The default is 75.

scene

self.scene= anInteger

Description

Used in conjunction with number_scenes to specify the range of frames to be extracted when constituting a multi-frame image.

Note

This attribute replaces the subimage attribute, which is deprecated in ImageMagick 5.5.6 and later. If scene is used with a version of ImageMagick prior to 5.5.6, it is a synonym for the subimage attribute.

server_name

self.server_name= aString

Description

Set the X11 display to obtain fonts from.

size

self.size= aString or aGeometry

Description

Set the width and height of the image when reading a built-in image format that does not have an inherent size, or when reading an image from a multi-resolution file format such as Photo CD, JBIG, or JPEG.

Arguments

A geometry string or a Geometry object.

subimage

self.subimage= anInteger

Description

Specify a base image of an image sequence in a multi-frame image.

Note

This attribute is deprecated in ImageMagick 5.5.6 and later. Use the scene attribute instead.

subrange

self.subrange= anInteger

Description

Specify the number of images relative to the base image. See subimage.

Note

This attribute is deprecated in ImageMagick 5.5.6 and later. Use the number_scenes attribute instead.

tile

self.tile= aString or aGeometry

Description

Specify a portion of an image to be extracted when the image is constituted. The argument is a geometry string. For example: self.tile = "200x200+100+100". This attribute can be used to identify a subset of an image that is otherwise too large to keep in memory.

Arguments

A geometry string or a Geometry object.

Note

This attribute is deprecated in ImageMagick 5.5.6 and later. Use the extract attribute instead.

units

self.units= aResolutionType

Description

Specify the units of image resolution.

Arguments

A ResolutionType constant.

view

self.view= aString

Description

FlashPix viewing parameters.