matlab\imagesci – Функции изображения и ввода/вывода данных

Image file import/export

<imformats> - List details about supported file formats.

IMFORMATS Manage file format registry.

FORMATS = IMFORMATS returns a structure containing all of the values in

the file format registry. The fields in this structure are:

ext - A cell array of file extensions for this format

isa - Function to determine if a file "IS A" certain type

info - Function to read information about a file

read - Function to read image data a file

write - Function to write MATLAB data to a file

alpha - 1 if the format has an alpha channel, 0 otherwise

description - A text description of the file format

The values for the isa, info, read, and write fields must be functions

which are on the MATLAB search path or function handles.

FORMATS = IMFORMATS(FMT) searches the known formats for a format with

extension given in the string "FMT." If found, a structure is returned

containing the characteristics and function names. Otherwise an empty

structure is returned.

FORMATS = IMFORMATS(FORMAT_STRUCT) sets the format registry to contain

the values in the "FORMAT_STRUCT" structure. The output structure

FORMATS contains the new registry settings. See the "Warning" statement

below.

FORMATS = IMFORMATS('add', FORMAT_STRUCT) adds the values in the

"FORMAT_STRUCT" structure to the format registry.

FORMATS = IMFORMATS('factory') resets the file format registry to the

default format registry values. This removes any user-specified

settings.

FORMATS = IMFORMATS('remove', FMT) removes the format with extension

FMT from the format registry.

FORMATS = IMFORMATS('update', FMT, FORMAT_STRUCT) change the format

registry values for the format with extension FMT to have the values

stored in FORMAT_STRUCT.

IMFORMATS without any input or output arguments prettyprints a table of

file format information for the supported formats.

Warning:

Using IMFORMATS to change the format registry is an advanced feature.

Incorrect usage may prevent loading of image files. Use IMFORMATS

with the 'factory' setting to return the format registry to a workable

state.

Note:

Changes to the format registry do not persist between MATLAB sessions.

To have a format always available when you start MATLAB, add the

appropriate IMFORMATS commands to the startup.m file in

$MATLAB/toolbox/local.

See also imread, imwrite, imfinfo, fileformats, path.

Reference page in Help browser

doc imformats

<imfinfo> - Return information about graphics file.

IMFINFO Information about graphics file.

INFO = IMFINFO(FILENAME,FMT) returns a structure whose

fields contain information about an image in a graphics

file. FILENAME is a string that specifies the name of the

graphics file, and FMT is a string that specifies the format

of the file. The file must be in the current directory or in

a directory on the MATLAB path. If IMFINFO cannot find a

file named FILENAME, it looks for a file named FILENAME.FMT.

The possible values for FMT are contained in the file format

registry, which is accessed via the IMFORMATS command.

If FILENAME is a TIFF, HDF, ICO, GIF, or CUR file containing more

than one image, INFO is a structure array with one element for

each image in the file. For example, INFO(3) would contain

information about the third image in the file.

INFO = IMFINFO(FILENAME) attempts to infer the format of the

file from its content.

INFO = IMFINFO(URL,...) reads the image from an Internet URL.

The URL must include the protocol type (e.g., "http://").

The set of fields in INFO depends on the individual file and

its format. However, the first nine fields are always the

same. These common fields are:

Filename A string containing the name of the file

FileModDate A string containing the modification date of

the file

FileSize An integer indicating the size of the file in

bytes

Format A string containing the file format, as

specified by FMT; for formats with more than one

possible extension (e.g., JPEG and TIFF files),

the first variant in the registry is returned

FormatVersion A string or number specifying the file format

version

Width An integer indicating the width of the image

in pixels

Height An integer indicating the height of the image

in pixels

BitDepth An integer indicating the number of bits per

pixel

ColorType A string indicating the type of image; this could

include, but is not limited to, 'truecolor' for a

truecolor (RGB) image, 'grayscale', for a grayscale

intensity image, or 'indexed' for an indexed image.

If FILENAME contains Exif tags (JPEG and TIFF only), then the INFO

struct may also contain 'DigitalCamera' or 'GPSInfo' (global

positioning system information) fields.

The value of the GIF format's 'DelayTime' field is given in hundredths

of seconds.

Example:

info = imfinfo('ngc6543a.jpg');

See also imread, imwrite, imformats.

Reference page in Help browser

doc imfinfo

<imread> - Read image from graphics file.

IMREAD Read image from graphics file.

A = IMREAD(FILENAME,FMT) reads a grayscale or color image from the file

specified by the string FILENAME. If the file is not in the current

directory, or in a directory on the MATLAB path, specify the full

pathname.

The text string FMT specifies the format of the file by its standard

file extension. For example, specify 'gif' for Graphics Interchange

Format files. To see a list of supported formats, with their file

extensions, use the IMFORMATS function. If IMREAD cannot find a file

named FILENAME, it looks for a file named FILENAME.FMT.

The return value A is an array containing the image data. If the file

contains a grayscale image, A is an M-by-N array. If the file contains

a truecolor image, A is an M-by-N-by-3 array. For TIFF files containing

color images that use the CMYK color space, A is an M-by-N-by-4 array.

See TIFF in the Format-Specific Information section for more

information.

The class of A depends on the bits-per-sample of the image data,

rounded to the next byte boundary. For example, IMREAD returns 24-bit

color data as an array of uint8 data because the sample size for each

color component is 8 bits. See the Remarks section for a discussion of

bitdepths, and see the Format-Specific Information section for more

detail about supported bitdepths and sample sizes for a particular

format.

[X,MAP] = IMREAD(FILENAME,FMT) reads the indexed image in FILENAME into

X and its associated colormap into MAP. Colormap values in the image

file are automatically rescaled into the range [0,1].

[...] = IMREAD(FILENAME) attempts to infer the format of the file

from its content.

[...] = IMREAD(URL,...) reads the image from an Internet URL. The

URL must include the protocol type (e.g., "http://").

Remarks

Bitdepth is the number of bits used to represent each image pixel.

Bitdepth is calculated by multiplying the bits-per-sample with the

samples-per-pixel. Thus, a format that uses 8-bits for each color

component (or sample) and three samples per pixel has a bitdepth of 24.

Sometimes the sample size associated with a bitdepth can be ambiguous:

does a 48-bit bitdepth represent six 8-bit samples or three 16-bit

samples? The following format-specific sections provide sample size

information to avoid this ambiguity.

Format-Specific Information (Listed Alphabetically by Format)

BMP -- Windows Bitmap

Supported Compression Output

Bitdepths None RLE Class Notes

-----------------------------------------------------------------------

1-bit x - logical

4-bit x x uint8

8-bit x x uint8

16-bit x - uint8 1 sample/pixel

24-bit x - uint8 3 samples/pixel

32-bit x - uint8 3 samples/pixel (1 byte padding)

CUR -- Cursor File

Supported Compression Output

Bitdepths None Compressed Class

--------------------------------------------------

1-bit x - logical

4-bit x - uint8

8-bit x - uint8

Special syntaxes:

[...] = IMREAD(...,IDX) reads in one image from a multi-image icon or

cursor file. IDX is an integer value that specifies the order that the

image appears in the file. For example, if IDX is 3, IMREAD reads the

third image in the file. If you omit this argument, IMREAD reads the

first image in the file.

[A,MAP,ALPHA] = IMREAD(...) returns the AND mask for the resource,

which can be used to determine transparency information. For cursor

files, this mask may contain the only useful data.

GIF -- Graphics Interchange Format

Supported Compression Output

Bitdepths None Compressed Class

--------------------------------------------------

1-bit x - logical

2-to-8 bit x - uint8

Special syntaxes:

[...] = IMREAD(...,IDX) reads in one or more frames from a multiframe

(i.e., animated) GIF file. IDX must be an integer scalar or vector of

integer values. For example, if IDX is 3, IMREAD reads the third image

in the file. If IDX is 1:5, only the first five frames are returned.

[...] = IMREAD(...,'Frames',IDX) is the same as the syntax above except

that IDX can be 'all'. In this case, all of the frames are read and

returned in the order that they appear in the file.

Note: Because of the way GIF files are structured, all of the frames

must be read when a particular frame is requested. Consequently, it is

much faster to specify a vector of frames or 'all' for IDX than to call

IMREAD in a loop when reading multiple frames from the same GIF file.

HDF -- Hierarchical Data Format

Supported Raster image Raster image Output

Bitdepths with colormap without colormap Class Notes

---------------------------------------------------------------------------

8-bit x x uint8

24-bit - x uint8 3 samples/pixel

Special Syntaxes:

[...] = IMREAD(...,REF) reads in one image from a multi-image HDF file.

REF is an integer value that specifies the reference number used to

identify the image. For example, if REF is 12, IMREAD reads the image

whose reference number is 12. (Note that in an HDF file the reference

numbers do not necessarily correspond with the order of the images in

the file. You can use IMFINFO to match up image order with reference

number.) If you omit this argument, IMREAD reads the first image in

the file.

ICO -- Icon File

See CUR.

JPEG -- Joint Photographic Experts Group

Note: IMREAD can read any baseline JPEG image as well as JPEG images

with some commonly used extensions.

Supported Compression Output

Bitdepths Lossy Lossless Class Notes

------------------------------------------------------------------------------

8-bit x x uint8 Grayscale or RGB

12-bit x x uint16 Grayscale

16-bit - x uint16 Grayscale

36-bit x x uint16 RGB(Three 12-bit samples/pixel)

JPEG 2000 - Joint Photographic Experts Group 2000

Supported Compression Output

Bitdepths Lossy Lossless Class

(per sample)

----------------------------------------------------------

1-bit x x logical

2- to 8-bit x x uint8

9- to 16-bit x x uint16

Note: Indexed JPEG 2000 images are not supported. Only JP2 compatible

color spaces are supported for JP2/JPX files. Arbitrary channels are

supported for raw codestream J2C files.

Special Syntaxes

[...] = IMREAD(..., 'Param1', value1, 'Param2', value2, ...) uses

parameter-value pairs to control the read operation.

Parameter name Value

------------------- -----

'ReductionLevel' A non-negative integer specifying reduction in

the resolution of the image. For a reduction

level 'L', the image resolution is reduced by a

factor of 2^L. Its default value is 0 implying

no reduction. The reduction level is limited by

the total number of decomposition levels as

provided by 'WaveletDecompositionLevels' field

In the structure returned from imfinfo function.

'PixelRegion' {ROWS, COLS}. IMREAD returns the sub-image

specified by the boundaries in ROWS and COLS.

ROWS and COLS must both be two-element vectors

that denote the 1-based indices [START STOP]. If

'ReductionLevel' is greater than 0, then ROWS and

COLS are coordinates in the reduced-sized image.

'V79Compatible' A BOOL value. If true, image returned is color

converted to gray-scale or RGB image as consistent

with previous versions of IMREAD (MATLAB 7.9

[R2009b] and earlier). Otherwise raw color

image is returned. Default is false.

PBM -- Portable Bitmap

Supported Raw ASCII (Plain) Output

Bitdepths Binary Encoded Class

--------------------------------------------------

1-bit x x logical

PCX -- Windows Paintbrush

Supported Output

Bitdepths Class Notes

----------------------------------------------

1-bit logical Grayscale only

8-bit uint8 Grayscale or indexed

24-bit uint8 RGB (8-bit samples)

PGM -- Portable Graymap

Supported Raw ASCII (Plain) Output

Bitdepths Binary Encoded Class

-------------------------------------------------------

up to 16-bit x - uint8

Arbitrary - x

PNG -- Portable Network Graphics

Supported Output

Bitdepths Class Notes

-------------------------------------------

1-bit logical Grayscale only

2-bit uint8 Grayscale only

4-bit uint8 Grayscale only

8-bit uint8 Grayscale or Indexed

16-bit uint16 Grayscale or Indexed

24-bit uint8 RGB (Three 8-bit samples/pixel)

48-bit uint16 RGB (Three 16-bit samples/pixel)

Special Syntaxes:

[...] = IMREAD(...,'BackgroundColor',BG) composites any transparent

pixels in the input image against the color specified in BG. If BG is

'none', then no compositing is performed. Otherwise, if the input image

is indexed, BG should be an integer in the range [1,P] where P is the

colormap length. If the input image is grayscale, BG should be an

integer in the range [0,1]. If the input image is RGB, BG should be a

three-element vector whose values are in the range [0,1]. The string

'BackgroundColor' may be abbreviated.

If the ALPHA output argument is used (see below), then BG defaults to

'none' if not specified by the user. Otherwise, if the PNG file

ontains a background color chunk, that color is used as the default

value for BG. If ALPHA is not used and the file does not contain a

background color chunk, then the default value for BG is 1 for indexed

images; 0 for grayscale images; and [0 0 0] for RGB images.

[A,MAP,ALPHA] = IMREAD(...) returns the alpha channel if one is

present; otherwise ALPHA is []. If 'BackgroundColor' is specified by

the user then ALPHA is []. Note that MAP may be empty if the file

contains a grayscale or truecolor image.

PPM -- Portable Pixmap

Supported Raw ASCII (Plain) Output

Bitdepths Binary Encoded Class

----------------------------------------------------

up to 16-bit x - uint8

Arbitrary - x

RAS -- Sun Raster

Supported Output

Bitdepths Class Notes

----------------------------------------------------

1-bit logical Bitmap

8-bit uint8 Indexed

24-bit uint8 RGB (8-bit samples)

32-bit uint8 RGB with Alpha (8-bit samples)

TIFF -- Tagged Image File Format

Supported Compression Output Bitdepths None Packbits CCITT RGB ICCLAB CIELAB CMYK Class Notes

-------------------------------------------------------------------------------------------------

1-bit x x x - - - - logical

8-bit x x - - - - - uint8

12-bit - - - - - - - uint16 Grayscale

or Indexed

16-bit - - - - - - - uint16 Grayscale

or Indexed

24-bit x x - x x x - uint8 3 samples

32-bit - - - - - - x uint8 4 samples

36-bit - - - x - - - uint16 3 samples

48-bit - - - x x x - uint16 3 samples

64-bit - - - - - - x double 4 samples

NOTE: IMREAD supports 8-bit integral and 32-bit floating point tiled

TIFF images, with any compression and colorspace combination listed

above, and 32-bit IEEE floating point images.

Special Syntaxes:

A = IMREAD(...) returns color data that uses the RGB, CIELAB, ICCLAB,

or CMYK color spaces. If the color image uses the CMYK color space, A

is an M-by-N-by-4 array.

[...] = IMREAD(..., 'Param1', value1, 'Param2', value2, ...) uses

parameter-value pairs to control the read operation. There are three

different parameters you can use:

Parameter name Value

-------------------- -----

'Index' A positive integer specifying which image to read in

a multi-image TIFF file. For example, if 'Index' is

3, IMREAD reads the third image in the file.

'Info' A structure array; the output of IMFINFO. When

reading images from a multi-image TIFF file, passing

the output of IMFINFO as the 'Info' parameter helps

IMREAD locate the images in the file more quickly.

'PixelRegion' {ROWS, COLS}. IMREAD returns the sub-image

specified by the boundaries in ROWS and COLS. ROWS

and COLS must be either two- or three-element

vectors. If two elements are provided, they denote

the 1-based indices [START STOP]. If three elements

are provided, the indices [START INCREMENT STOP]

allow image downsampling.

XWD -- X Window Dump

Supported Output

Bitdepths ZPixmaps XYBitmaps XYPixmaps Class

--------------------------------------------------------------------

1-bit x - x logical

8-bit x - - uint8

Please read the file libtiffcopyright.txt for more information.

Example:

imdata = imread('ngc6543a.jpg');

See also imfinfo, imwrite, imformats, fread, image, double, uint8.

Reference page in Help browser

doc imread

<imwrite> - Write image to graphics file.

IMWRITE Write image to graphics file.

IMWRITE(A,FILENAME,FMT) writes the image A to the file specified by

FILENAME in the format specified by FMT.

A can be an M-by-N (grayscale image) or M-by-N-by-3 (color image)

array. A cannot be an empty array. If the format specified is TIFF,

IMWRITE can also accept an M-by-N-by-4 array containing color data

that uses the CMYK color space.

FILENAME is a string that specifies the name of the file.

FMT is a string specifying the format of the file. See the reference

page, or the output of the IMFORMATS function, for a list of

supported formats.

IMWRITE(X,MAP,FILENAME,FMT) writes the indexed image in X and its

associated colormap MAP to FILENAME in the format specified by FMT.

If X is of class uint8 or uint16, IMWRITE writes the actual values in

the array to the file. If X is of class double, IMWRITE offsets the

values in the array before writing, using uint8(X-1). MAP must be a

valid MATLAB colormap. Note that most image file formats do not

support colormaps with more than 256 entries.

When writing multiframe GIF images, X should be an 4-dimensional

M-by-N-by-1-by-P array, where P is the number of frames to write.

IMWRITE(...,FILENAME) writes the image to FILENAME, inferring the

format to use from the filename's extension. The extension must be

one of the legal values for FMT.

IMWRITE(...,PARAM1,VAL1,PARAM2,VAL2,...) specifies parameters that

control various characteristics of the output file. Parameters are

currently supported for GIF, HDF, JPEG, TIFF, PNG, PBM, PGM, and PPM

files.

Class Support

-------------

The input array A can be of class logical, uint8, uint16, or double.

Indexed images (X) can be of class uint8, uint16, or double; the

associated colormap, MAP, must be double. Input values must be

full (non-sparse).

The class of the image written to the file depends on the format

specified. For most formats, if the input array is of class uint8,

IMWRITE outputs the data as 8-bit values. If the input array is of

class uint16 and the format supports 16-bit data (JPEG, PNG, and

TIFF), IMWRITE outputs the data as 16-bit values. If the format does

not support 16-bit values, IMWRITE issues an error. Several formats,

such as JPEG and PNG, support a parameter that lets you specify the

bit depth of the output data.

If the input array is of class double, and the image is a grayscale

or RGB color image, IMWRITE assumes the dynamic range is [0,1] and

automatically scales the data by 255 before writing it to the file as

8-bit values.

If the input array is of class double, and the image is an indexed

image, IMWRITE converts the indices to zero-based indices by

subtracting 1 from each element, and then writes the data as uint8.

If the input array is of class logical, IMWRITE assumes the data is a

binary image and writes it to the file with a bit depth of 1, if the

format allows it. BMP, PNG, or TIFF formats accept binary images as

input arrays.

GIF-specific parameters

-----------------------

'WriteMode' One of these strings: 'overwrite' (the default)

or 'append'. In append mode, a single frame is

added to the existing file.

'Comment' A string or cell array of strings containing a

comment to be added to the image. For a cell

array of strings, a carriage return is added

after each row.

'DisposalMethod' One of the following strings, which sets the

disposal method of an animated GIF:

'leaveInPlace', 'restoreBG', 'restorePrevious',

or 'doNotSpecify'.

'DelayTime' A scalar value between 0 and 655 inclusive, which

specifies the delay in seconds before displaying

the next image.

'TransparentColor' A scalar integer. This value specifies which

index in the colormap should be treated as the

transparent color for the image. If X is uint8

or logical, then indexing starts at 0. If X is

double, then indexing starts at 1.

'BackgroundColor' A scalar integer. This value specifies which

index in the colormap should be treated as the

background color for the image and is used for

certain disposal methods in animated GIFs. If X

is uint8 or logical, then indexing starts at 0.

If X is double, then indexing starts at 1.

'LoopCount' A finite integer between 0 and 65535 or the value

Inf (the default) which specifies the number of

times to repeat the animation. By default, the

animation will continuously loop. For a value of

0, the animation will be played once. For a

value of 1, the animation will be played twice,

etc.

'ScreenSize' A two element vector specifying the screen height

and width of the frame. When used with

'Location', this provides a way to write frames

to the image which are smaller than the whole

frame. The remaining values are filled in

according to the 'DisposalMethod'.

'Location' A two element vector specifying the offset of the

top left corner of the screen relative to the top

left corner of the image. The first element is

the offset from the top, and the second element

is the offset from the left.

HDF-specific parameters

-----------------------

'Compression' One of these strings: 'none' (the default),

'rle' (only valid for grayscale and indexed

images), 'jpeg' (only valid for grayscale

and RGB images)

'Quality' A number between 0 and 100; parameter applies

only if 'Compression' is 'jpeg'; higher

numbers mean quality is better (less image

degradation due to compression), but the

resulting file size is larger

'WriteMode' One of these strings: 'overwrite' (the

default) or 'append'

JPEG-specific parameters

------------------------

'Quality' A number between 0 and 100; higher numbers

mean quality is better (less image degradation

due to compression), but the resulting file

size is larger

'Comment' A column vector cell array of strings or a

char matrix. Each row of input is written out

as a comment in the JPEG file.

'Mode' Either 'lossy' (the default) or 'lossless'

'BitDepth' A scalar value indicating desired bitdepth;

for grayscale images this can be 8, 12, or 16;

for truecolor images this can be 8 or 12. Only

lossless mode is supported for 16-bit images.

JPEG2000-specific parameters

----------------------------

'Mode' Either 'lossy' (the default) or 'lossless'.

'CompressionRatio' A real value greater than 1 specifying the target

compression ratio which is defined as the ratio of

input image size to the output compressed size. For

example, a value of 2.0 implies that the output

image size will be half of the input image size or

less. A higher value implies a smaller file size and

reduced image quality. This is valid only with

'lossy' mode. Note that the compression ratio

doesn't take into account the header size, and hence

in some cases the output file size can be larger

than expected.

'ProgressionOrder' A string that is one of 'LRCP', 'RLCP', 'RPCL',

'PCRL' or 'CPRL'. The four character identifiers are

interpreted as L=layer, R=resolution, C=component

and P=position. The first character refers to the

index which progresses most slowly, while the last

refers to the index which progresses most quickly.

The default value is 'LRCP'.

'QualityLayers' A positive integer (not exceeding 20) specifying the

number of quality layers. The default value is 1.

'ReductionLevels' A positive integer (not exceeding 8) specifying the

number of reduction levels or the wavelet

decomposition levels.

'TileSize' A 2-element vector specifying tile height and tile

width. The minimum tile size that can be specified

is [128 128]. The default tile size is same as the

image size.

'Comment' A cell array of strings or a char matrix. Each row

of input is written out as a comment in the JPEG2000

file.

TIFF-specific parameters

------------------------

'Colorspace' One of these strings: 'rgb', 'cielab', or

'icclab'. The default value is 'rgb'. This

parameter is used only when the input array,

A, is M-by-N-by-3. See the reference page

for more details about creating L*a*b* TIFF

files.

In order to create a CMYK TIFF, the colorspace

parameter should not be used. It is sufficient

to specify the input array A as M-by-N-by-4.

'Compression' One of these strings: 'none', 'packbits'

(default for nonbinary images), 'lzw', 'deflate',

'jpeg', 'ccitt' (default for binary images),

'fax3', 'fax4'; 'ccitt', 'fax3', and

'fax4' are valid for binary images only.

'jpeg' is a lossy compression scheme; other

compression modes are lossless.

When using JPEG compression, the 'RowsPerStrip'

parameter must be specified and must be a multiple

of 8.

'Description' Any string; fills in the ImageDescription

field returned by IMFINFO

'Resolution' A two-element vector containing the

XResolution and YResolution, or a scalar

indicating both resolutions; the default value

is 72

'RowsPerStrip' A scalar value. The default will be such that each

strip is about 8K bytes.

'WriteMode' One of these strings: 'overwrite' (the

default) or 'append'

PNG-specific parameters

-----------------------

'Author' A string

'Description' A string

'Copyright' A string

'CreationTime' A string

'ImageModTime' A MATLAB datenum or a string convertible to a

date vector via the DATEVEC function. Values

should be in UTC time.

'Software' A string

'Disclaimer' A string

'Warning' A string

'Source' A string

'Comment' A string

'InterlaceType' Either 'none' or 'adam7'

'BitDepth' A scalar value indicating desired bitdepth;

for grayscale images this can be 1, 2, 4,

8, or 16; for grayscale images with an

alpha channel this can be 8 or 16; for

indexed images this can be 1, 2, 4, or 8;

for truecolor images with or without an

alpha channel this can be 8 or 16

'Transparency' This value is used to indicate transparency

information when no alpha channel is used.

For indexed images: a Q-element vector in

the range [0,1]; Q is no larger than the

colormap length; each value indicates the

transparency associated with the

corresponding colormap entry

For grayscale images: a scalar in the range

[0,1]; the value indicates the grayscale

color to be considered transparent

For truecolor images: a 3-element vector in

the range [0,1]; the value indicates the

truecolor color to be considered

transparent

You cannot specify 'Transparency' and

'Alpha' at the same time.

'Background' The value specifies background color to be

used when compositing transparent pixels.

For indexed images: an integer in the range

[1,P], where P is the colormap length

For grayscale images: a scalar in the range

[0,1]

For truecolor images: a 3-element vector in

the range [0,1]

'Gamma' A nonnegative scalar indicating the file

gamma

'Chromaticities' An 8-element vector [wx wy rx ry gx gy bx

by] that specifies the reference white

point and the primary chromaticities

'XResolution' A scalar indicating the number of

pixels/unit in the horizontal direction

'YResolution' A scalar indicating the number of

pixels/unit in the vertical direction

'ResolutionUnit' Either 'unknown' or 'meter'

'Alpha' A matrix specifying the transparency of

each pixel individually; the row and column

dimensions must be the same as the data

array; may be uint8, uint16, or double, in

which case the values should be in the

range [0,1]

'SignificantBits' A scalar or vector indicating how many

bits in the data array should be regarded

as significant; values must be in the range

[1,bitdepth]

For indexed images: a 3-element vector

For grayscale images: a scalar

For grayscale images with an alpha channel:

a 2-element vector

For truecolor images: a 3-element vector

For truecolor images with an alpha channel:

a 4-element vector