readimage

Read specified image from datastore

Syntax

img = readimage(imds,I)

[img,fileinfo] = readimage(imds,I)

Description

img = readimage(imds,I) reads the Ith image file from the datastore imds and returns the image data img. The size and data type of the img array depends on the image formats of the files in the datastore. The image formats supported by readimage function are those formats supported by imread. For more information on the supported formats, see imread.

[img,fileinfo] = readimage(imds,I) also returns a struct fileinfo that contains two file information fields:

• Filename — Name of the file from which the image is read.

• FileSize — Size of the file in bytes.

Examples

Read Specified Image

Create an ImageDatastore object containing two images, and then read and view the second image.

imds = imageDatastore({'street1.jpg','street2.jpg'});
img = readimage(imds,2);
imshow(img)

File Information

Create a datastore object containing two images and read the second image.

imds = imageDatastore({'street1.jpg','street2.jpg'});
[img,info] = readimage(imds,2);

The info structure contains the following information for the second image: Filename, FileSize, and Label. To display the filename and path, type info.Filename in the command window. To display the file size, type info.FileSize.

Input Arguments

imds — Input datastore

ImageDatastore object

Input datastore. You can use the imageDatastore function or the datastore function to create a datastore object from your data.

I — Image file index

positive integer

Image file index, specified as a positive integer.

Data Types: double

Output Arguments

img — Image data

multidimensional array of integers

Image data, returned as a multidimensional array of integers. The size of img depends on the image format:

• m-by-n array for grayscale images

• m-by-n-by-3 array for truecolor images

• m-by-n-by-4 array for CMYK Tiff images

The readimage function supports the image formats that imread supports. For more information on the supported formats, see imread.

Data Types: double

fileinfo — File information

structure array

File information, returned as a structure array containing two fields:

• Filename — Name of the file from which the image is read.

• FileSize — Size of the file in bytes.

Data Types: struct

Extended Capabilities

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Usage notes and limitations:

• readimage does not support the following image formats in a thread-based environment:

  • Hierarchical Data Format (HDF)

  • SVS

  • TIFF

For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced in R2015b