imfinfo

Information about graphics file

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Syntax

info = imfinfo(filename)
info = imfinfo(filename,fmt)

Description

example

info = imfinfo(filename) returns a structure whose fields contain information about an image in a graphics file, filename.

The format of the file is inferred from its contents.

  • If filename is a TIFF, PGM, PBM, PPM, HDF, ICO, GIF, SVS, or CUR file containing more than one image, then 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,fmt) additionally looks for a file named filename.fmt, if MATLAB® cannot find a file named filename.

Examples

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Open Live Script

Find information about the example image, ngc6543a.jpg.

info = imfinfo('ngc6543a.jpg');

The info structure contains the following information fields: Filename, FileModDate, FileSize, Format, FormatVersion, Width, Height, BitDepth, ColorType, FormatSignature, NumberOfSamples, CodingMethod, CodingProcess, and Comment.

To display information from the structure, for example CodingMethod, type info.CodingMethod in the command window.

info.CodingMethod
ans = 
'Huffman'

To display all the properties in the structure, type info in the command window.

Input Arguments

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Name of graphics file, specified as a character vector or string scalar.

Depending on the location of the file, filename can take on one of these forms.

Location

Form

Current folder or folder on the MATLAB path

Specify the name of the file in filename.

Example: 'myImage.jpg'

File in a folder

If the file is not in the current folder or in a folder on the MATLAB path, then specify the full or relative path name.

Example: 'C:\myFolder\myImage.ext'

Example: '\imgDir\myImage.ext'

URL

If the file is located by an internet URL, then filename must contain the protocol type such as, http://.

Example: 'http://hostname/path_to_file/my_image.jpg'

Remote Location

If the file is stored at a remote location, then filename must contain the full path of the file specified as a uniform resource locator (URL) of the form:

scheme_name://path_to_file/my_file.ext

Based on your remote location, scheme_name can be one of the values in this table.

Remote Locationscheme_name
Amazon S3™s3
Windows Azure® Blob Storagewasb, wasbs
HDFS™hdfs

For more information, see Work with Remote Data.

Example: 's3://bucketname/path_to_file/my_image.jpg'

Data Types: char | string

Image format, specified as a character vector or string scalar. The possible values for fmt are contained in the MATLAB file format registry. To view of list of these formats, run the imformats command.

Example: 'gif'

Data Types: char | string

Output Arguments

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Information about the graphics file, returned as a structure array. The set of fields in info depends on the individual file and its format. This table lists the nine fields that always appear, and describes their values.

Field Name

Description

Value

Filename

Name of the file or the internet URL specified. If the file is not in the current folder, the character vector contains the full path name of the file.

character vector

FileModDate

Date when the file was last modified.

character vector

FileSize

Size of the file, in bytes.

integer

Format

File format, as specified by fmt. For formats with more than one possible extension (for example, JPEG and TIFF files), imfinfo returns the first variant in the file format registry.

character vector

FormatVersion

File format version.

character vector or number

Width

Image width, in pixels.

integer

Height

Image height, in pixels.

integer

BitDepth

Number of bits per pixel.

integer

ColorType

Image type. ColorType includes, but is not limited to, 'truecolor' for a truecolor (RGB) image, 'grayscale' for a grayscale intensity image, or 'indexed' for an indexed image.

character vector

Additional fields returned by some file formats:

  • JPEG and TIFF only — If filename contains Exchangeable Image File Format (EXIF) tags, then info might also contain 'DigitalCamera' or 'GPSInfo' (global positioning system information) fields.

  • GIF only — imfinfo returns the value of the 'DelayTime' field in hundredths of seconds.

  • JPEG2000 only — The info structure contains an m-by-3 cell array, 'ChannelDefinition'. The first column of 'ChannelDefinition' reports a channel position as it exists in the file. The second column reports the type of channel, and the third column reports the channel mapping.

See Also

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Introduced before R2006a

MATLAB Documentation

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