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imshowpair

Compare differences between images

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Syntax

obj = imshowpair(A,B)
obj = imshowpair(A,RA,B,RB)
obj = imshowpair(___,method)
obj = imshowpair(___,Name,Value)

Description

obj = imshowpair(A,B) creates a composite RGB image showing A and B overlaid in different color bands. To choose another type of visualization of the two images, use the method argument. If A and B are different sizes, imshowpair pads the smaller dimensions with zeros on the bottom and right edges so that the two images are the same size. By default, imshowpair scales the intensity values of A and B independently from each other. imshowpair returns obj, an image object.

example

obj = imshowpair(A,RA,B,RB) displays the differences between images A and B, using the spatial referencing information provided in RA and RB. RA and RB are spatial referencing objects.

example

obj = imshowpair(___,method) uses the visualization method specified by method.

example

obj = imshowpair(___,Name,Value) specifies additional options with one or more Name,Value pair arguments, using any of the previous syntaxes.

example

Examples

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Open Live Script

Display a pair of grayscale images with two different visualization methods, "diff" and "blend".

Load an image into the workspace. Create a copy with a rotation offset applied.

A = imread("cameraman.tif");
B = imrotate(A,5,"bicubic","crop");

Display the difference of A and B.

imshowpair(A,B,"diff")

Figure contains an axes object. The hidden axes object contains an object of type image.

Display a blended overlay of A and B.

figure
imshowpair(A,B,"blend","Scaling","joint")

Figure contains an axes object. The hidden axes object contains an object of type image.

Open Live Script

Read an image. Create a copy and apply rotation and a brightness adjustment.

A = dicomread("CT-MONO2-16-ankle.dcm");
B = imrotate(A,10,"bicubic","crop");
B = B * 0.2;

In this example, we know that the resolution of images A and B is 0.2 mm. Provide this information using two spatial referencing objects.

RA = imref2d(size(A),0.2,0.2);
RB = imref2d(size(B),0.2,0.2);

Display the images with the default method ("falsecolor") and apply brightness scaling independently to each image. Specify the axes that will be the parent of the image object created by imshowpair.

figure;
hAx = axes;
imshowpair(A,RA,B,RB,"Scaling","independent","Parent",hAx);

Figure contains an axes object. The axes object contains an object of type image.

Input Arguments

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Image to be displayed, specified as a grayscale, truecolor, or binary image.

Image to be displayed, specified as a grayscale, truecolor, or binary image.

Spatial referencing information about an input image, specified as spatial referencing object, of class imref2d.

Spatial referencing information about an input image, specified as spatial referencing object, of class imref2d.

Visualization method to display combined images, specified as one of the following values. The images in the table compare the peppers image before and after applying a small vertical translation.

ValueDescriptionSample Display
"falsecolor"Overlay A and B in different color bands. Gray regions indicate where the images have the same intensity. Colored regions show where the intensities differ. Optionally specify the display colors using the ColorChannels argument. The function converts RGB images to grayscale before displaying them in falsecolor.

Original and vertically translated peppers image displayed using the falsecolor method

"blend"Overlay A and B using alpha blending. The intensity of the display is the mean of the two images.

Original and vertically translated peppers image displayed using the blend method

"checkerboard"Display an image with alternating rectangular regions from A and B.

Original and vertically translated peppers image displayed using the checkerboard method

"diff"Display a difference image from A and B. The function converts RGB images to grayscale before calculating the difference image.

Original and vertically translated peppers image displayed using the difference method

"montage"Place A and B next to each other in the same figure.

Original and translated peppers image displayed using the montage method

Data Types: char | string

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: "Scaling","joint" scales the intensity values of A and B together as a single data set.

Output color channel for each input image, specified as one of the values in the table. This argument only affects the visualization when method is specified as "falsecolor".

[R G B]A three element vector that specifies which image to assign to the red, green, and blue channels. The R, G, and B values must be 1 (for the first input image), 2 (for the second input image), and 0 (for neither image).
"red-cyan"A shortcut for the vector [1 2 2], which is suitable for red/cyan stereo anaglyphs.
"green-magenta"A shortcut for the vector [2 1 2], which is a high contrast option, ideal for people with many kinds of color blindness.

Interpolation technique used when scaling an image, specified as one of the following values.

ValueDescription
"nearest"Nearest neighbor interpolation (default)
"bilinear"Bilinear interpolation

Parent of image object created by imshowpair, specified as an axes object.

Intensity scaling option, specified as one of the following values.

"independent"Scales the intensity values of A and B independently from each other.
"joint"Scales the intensity values in the images jointly as if they were together in the same image. This option is useful when you want to visualize registrations of monomodal images, where one image contains fill values that are outside the dynamic range of the other image.
"none"No additional scaling.

Data Types: char | string

Output Arguments

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Visualization of two images, returned as an image object.

Tips

  • Use imfuse to create composite visualizations that you can save to a file. Use imshowpair to display composite visualizations to the screen.

  • Figure titles can appear cut off in the Live Editor. To ensure the whole title is visible, set the PositionContraint property of the parent axes object to "outerposition". Update the property value after the imshowpair function and before the title function.

    I = imread("peppers.png");
imshowpair(I,I)
ax = gca;
ax.PositionConstraint = "outerposition";
title("Peppers");
    If you specify the parent axes using the Parent name-value argument, set the PositionConstraint property of the specified parent axes object. For more details about axes position properties, see Control Axes Layout.

Version History

Introduced in R2012a

See Also

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