4 Displaying and Exploring Images

Viewing Image Sequences

In this section...

“Overview” on page 4-54

“Viewing Image Sequences in the Movie Player” on page 4-54 “Viewing Image Sequences as a Montage” on page 4-63 “Converting a Multiframe Image to a Movie” on page 4-64

Overview

Some applications create collections of images related by time, such as frames in a movie, or by (spatial location, such as magnetic resonance imaging (MRI) slices. These collections of images are referred to by a variety of names, such as image sequences, image stacks, or videos.

The toolbox represents image sequences as four-dimensional arrays, where each separate image is called a frame, all frames are the same size, and the frames are concatenated along the fourth dimension. imtool and imshow can display one frame at a time, using standard MATLAB array indexing syntax, but cannot animate the sequence or provide any navigation within the sequence. A better choice to view image sequences is the Movie Player (implay). The Movie Player can animate the display of frames in an image sequence and provides playback controls that you can use to navigate among the frames in the sequence. To get a static view of all the frames in an image sequence at one time, use the montage function. For more information, see these additional topics.

•“Viewing Image Sequences in the Movie Player” on page 4-54

•“Viewing Image Sequences as a Montage” on page 4-63.

•“Converting a Multiframe Image to a Movie” on page 4-64

Viewing Image Sequences in the Movie Player

This section describes how to use the Movie Player to view image sequences and provides information about configuring the Movie Player.

• “Example: Viewing a Sequence of MRI Images” on page 4-55

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Viewing Image Sequences

•“Configuring the Movie Player” on page 4-58

•“Specifying the Frame Rate” on page 4-61

•“Specifying the Color Map” on page 4-62

•“Getting Information about the Image Frame” on page 4-62

Example: Viewing a Sequence of MRI Images

1Load the image sequence into the MATLAB workspace. For this example, load the MRI data from the file mristack.mat, which is included in the imdemos directory.

load mristack

This places a variable named mristack in your workspace. The variable is an array of 21 grayscale frames containing MRI images of the brain. Each frame is a 256-by-256 array of uint8 data.

2View the image sequence in the Movie Player. Call implay, specifying the name of the image sequence variable as an argument. You can also specify the name of a file that contains an image sequence, such as an Audio Video Interleaved (AVI) file.

implay(mristack)

You can also import an image sequence from the workspace into the Movie Player using the Import from workspace option on the File menu.

The Movie Player opens, displaying the first frame of the image sequence. Note how the Movie Player displays information about the image sequence, such as the size of each frame and the total number of frames, at the bottom of the window.

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4 Displaying and Exploring Images

Toolbar

Playback toolbar

Movie frames

3Explore the image sequence using Movie Player Playback controls.

To view the image sequence or video as an animation, click the Play button in the Playback toolbar, select Play from the Playback menu, or press P or the Space bar. By default, the Movie Player plays the image sequence forward, once in its entirety, but you can view the frames in the image sequence in many ways, described in this table. As you view an image sequence, note how the Movie Player updates the Status Bar at the bottom of the window.

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Viewing Image Sequences

4 Change the view of the image sequence or examine a frame more closely.

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