Resize image - MATLAB imresize (2024)

Table of Contents

Syntax Description Examples Shrink Image By Factor of Two Using Default Interpolation Method Shrink Image Using Nearest-Neighbor Interpolation Resize RGB Image Specifying Size of Output Image Resize Indexed Image Input Arguments A — Image to be resized numeric array | logical array | categorical array scale — Resize factor positive number [numrows numcols] — Row and column dimensions of output image two-element vector of positive numbers X — Indexed image to be resized real, nonsparse numeric array map — Colormap associated with indexed image c-by-3 numeric matrix method — Interpolation method character vector | string scalar | two-element cell array Name-Value Arguments Antialiasing — Perform antialiasing when shrinking an image true | false Colormap — Return optimized colormap "optimized" (default) | "original" Dither — Perform color dithering true (default) | false Method — Interpolation method character vector | string scalar | cell array OutputSize — Size of output image two-element vector of positive numbers Scale — Resize scale factor positive number | two-element vector of positive numbers Output Arguments B — Resized image numeric array | logical array | categorical array Y — Resized indexed image numeric array newmap — Colormap of resized indexed image m-by-3 numeric matrix Extended Capabilities C/C++ Code Generation Generate C and C++ code using MATLAB® Coder™. GPU Code Generation Generate CUDA® code for NVIDIA® GPUs using GPU Coder™. Thread-Based Environment Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool. GPU Arrays Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™. Version History R2019a: Supports categorical images See Also Topics MATLAB Command Americas Europe Asia Pacific FAQs

Resize image

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Syntax

B = imresize(A,scale)

B = imresize(A,[numrows numcols])

[Y,newmap]= imresize(X,map,___)

___ = imresize(___,method)

___ = imresize(___,Name,Value)

Description

example

B = imresize(A,scale) returns image B that is scale times the size of image A. The input image A can be a grayscale, RGB, binary, or categorical image.

If A has more than two dimensions, then imresize only resizes the first two dimensions. If scale is between 0 and 1, then B is smaller than A. If scale is greater than 1, then B is larger than A. By default, imresize uses bicubic interpolation.

example

B = imresize(A,[numrows numcols]) returns image B that has the number of rows and columns specified by the two-element vector [numrows numcols].

example

[Y,newmap]= imresize(X,map,___) resizes the indexed image X where map is the colormap associated with the image.

example

___ = imresize(___,method) specifies the interpolation method used.

___ = imresize(___,Name,Value) returns the resized image where name-value arguments control various aspects of the resizing operation. Specify name-value arguments after all other input arguments.

Examples

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Shrink Image By Factor of Two Using Default Interpolation Method

Open Live Script

Load image into the workspace.

I = imread('ngc6543a.jpg');

Shrink the image by a factor of two.

J = imresize(I, 0.5);

Display the original image and the resized image.

figure, imshow(I), figure, imshow(J)

Shrink Image Using Nearest-Neighbor Interpolation

Open Live Script

Load an image into the workspace.

I = imread('ngc6543a.jpg');

Shrink the image to 40% of the original size using nearest-neighbor interpolation. This is the fastest method, but it has the lowest quality.

J = imresize(I,0.4,'nearest');

Display the original image and the resized image.

imshow(I)title('Original Image')

imshow(J)title('Resized Image Using Nearest Neighbor Interpolation')

Resize RGB Image Specifying Size of Output Image

Open Live Script

Read an RGB image into the workspace.

RGB = imread('peppers.png');

Resize the RGB image to have 64 rows. imresize calculates the number of columns automatically.

RGB2 = imresize(RGB,[64 NaN]);

Get the size of the resized image.

sz = size(RGB2)

sz = 1×3 64 86 3

Display the original image and the resized image.

imshow(RGB)title("Original Image")

imshow(RGB2)title("Resized Image with 64 Rows")

Resize Indexed Image

Open Live Script

Read an indexed image into the workspace.

[X,map] = imread("corn.tif");

Increase the size of the indexed image by 50%.

[Y,newmap] = imresize(X,map,1.5);

Display the original image and the resized image.

imshow(X,map)title("Original Indexed Image and Colormap")

imshow(Y,newmap)title("Resized Image and Optimized Colormap")

Input Arguments

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`A` — Image to be resized
numeric array | logical array | categorical array

Image to be resized, specified as a numeric array, logical array, or categorical array of any dimension. Input must be nonsparse, and numeric input must be real.

`scale` — Resize factor
positive number

Resize factor, specified as a positive number. imresize applies the same scale factor to the row and column dimensions. To apply a different resize factor to each dimension, use the Scale name-value argument.

If you specify a resize factor that does not result in integer-length image dimensions, then imresize follows the resizing operation with a call to the ceil function. In other words, the output image has ceil(scale*size(A,1)) rows and ceil(scale*size(A,2)) columns.

`[numrows numcols]` — Row and column dimensions of output image
two-element vector of positive numbers

Row and column dimensions of output image, specified as a two-element vector of positive numbers. You can specify the value NaN for either numrows or numcols. In this case, imresize calculates the number of rows or columns for that dimension automatically, preserving the aspect ratio of the image.

`X` — Indexed image to be resized
real, nonsparse numeric array

Indexed image to be resized, specified as a real, nonsparse numeric array of positive integers.

Data Types: double | uint8 | uint16

`map` — Colormap associated with indexed image
c-by-3 numeric matrix

Colormap associated with indexed image X, specified as a c-by-3 numeric matrix with values in the range [0, 1]. Each row is a three-element RGB triplet that specifies the red, green, and blue components of a single color of the colormap.

Data Types: double

`method` — Interpolation method
character vector | string scalar | two-element cell array

Interpolation method, specified as a character vector, string scalar, or two-element cell array. The default value for numeric and logical images is "bicubic". The default value for categorical images is "nearest". Categorical images only support the values "nearest" and "box".

When method is a character vector or string scalar, it identifies a particular method or named interpolation kernel, listed in the following table.

Method	Description
`"nearest"`	Nearest-neighbor interpolation; the output pixel is assigned the value of the pixel that the point falls within. No other pixels are considered.
`"bilinear"`	Bilinear interpolation; the output pixel value is a weighted average of pixels in the nearest 2-by-2 neighborhood.
`"bicubic"`	Bicubic interpolation; the output pixel value is a weighted average of pixels in the nearest 4-by-4 neighborhood. Note Bicubic interpolation can produce pixel values outside the original range.
Interpolation Kernel	Description
`"box"`	Box-shaped kernel
`"triangle"`	Triangular kernel (equivalent to `"bilinear"`)
`"cubic"`	Cubic kernel (equivalent to `"bicubic"`)
`"lanczos2"`	Lanczos-2 kernel
`"lanczos3"`	Lanczos-3 kernel

When method is a two-element cell array, it defines a custom interpolation kernel. The cell array has the form {f,w}, where f is a function handle for a custom interpolation kernel and w is the width of the custom kernel. f(x) must be zero outside the interval -w/2 <= x < w/2. The function handle f can be called with a scalar or a vector input. For user-specified interpolation kernels, the output image can have some values slightly outside the range of pixel values in the input image.

For more information about the built-in and custom interpolation kernels, see Create and Compare Resizing Interpolation Kernels.

Data Types: char | string | cell

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.

Example: B = imresize(A,0.5,Antialiasing=false) does not perform antialiasing when shrinking an image.

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

Example: B = imresize(A,0.5,"Antialiasing",false) does not perform antialiasing when shrinking an image.

`Antialiasing` — Perform antialiasing when shrinking an image
`true` | `false`

Perform antialiasing when shrinking an image, specified as true or false.

If the interpolation method is "nearest", then the default value of Antialiasing is false.
If the interpolation method is "box" and the input image is categorical, then the default value of Antialiasing is false.
For all other interpolation methods, the default value is true.

Data Types: logical

`Colormap` — Return optimized colormap
`"optimized"` (default) | `"original"`

Return optimized or original colormap for indexed image, specified as one of the following values.

Value	Description
`"original"`	The output colormap newmap is the same as the input colormap map.
`"optimized"`	`imresize` returns a new optimized colormap.

The Colormap argument is valid only when resizing indexed images.

Data Types: char | string

`Dither` — Perform color dithering
`true` (default) | `false`

Perform color dithering, specified as true or false. In dithering, you apply a form of noise to the image to randomize quantization error and prevent large-scale patterns.

The Dither argument is valid only when resizing indexed images.

Data Types: logical

`Method` — Interpolation method
character vector | string scalar | cell array

Interpolation method, specified as a character vector, string scalar, or two-element cell array. For details, see method.

Data Types: char | string | cell

`OutputSize` — Size of output image
two-element vector of positive numbers

Size of the output image, specified as a two-element vector of positive numbers. For details, see [numrows numcols].

`Scale` — Resize scale factor
positive number | two-element vector of positive numbers

Resize scale factor, specified as a positive number or two-element vector of positive numbers. If you specify a scalar, then imresize applies the same scale factor to the row and column dimensions. If you specify a two-element vector, then imresize applies a different scale value to each dimension.

If you specify a resize scale factor that does not result in integer-length image dimensions, then imresize follows the resizing operation with a call to the ceil function. In other words, the output image has ceil(Scale(1)*size(A,1)) rows and ceil(Scale(2)*size(A,2)) columns.

Output Arguments

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`B` — Resized image
numeric array | logical array | categorical array

Resized image, returned as a numeric, logical, or categorical array of the same data type as the input image, A.

`Y` — Resized indexed image
numeric array

Resized indexed image, returned as a numeric array of the same data type as the input indexed image, X.

`newmap` — Colormap of resized indexed image
m-by-3 numeric matrix

Colormap of the resized indexed image Y, returned as an m-by-3 numeric matrix. By default, imresize returns a new, optimized colormap with the resized image. To return a colormap that is the same as the original colormap, use the Colormap name-value argument.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Syntaxes that support indexed images are not supported, including the name-value arguments Colormap and Dither.
Custom interpolation kernels are not supported.
All name-value arguments must be compile-time constants.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

Colormap and Dither name-value arguments are not supported.
Indexed images are not supported.
Custom interpolation kernels are not supported.
All name-value pairs must be compile-time constants.
For certain interpolation kernels, there can be a small numerical mismatch between the results in MATLAB^® and the generated code.

Thread-Based Environment
Run code in the background using MATLAB® `backgroundPool` or accelerate code with Parallel Computing Toolbox™ `ThreadPool`.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

gpuArray input with more than 2²⁷ elements is not supported.
gpuArray input must be non-sparse.
gpuArray input with underlying type categorical is not supported.
Indexed images are not supported on a GPU.
If you use bicubic interpolation, the output image can have some values slightly outside the range of pixel values in the input image.
There is a slight numerical difference between the results of imresize on a CPU and a GPU. These differences occur on the right and bottom borders of the image and are barely noticeable to the naked eye.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a

expand all

R2019a: Supports categorical images

The imresize function now supports categorical images.

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FAQs

How do I resize an image in Matlab? ›

B = imresize( A , scale ) returns image B that is scale times the size of image A . The input image A can be a grayscale, RGB, binary, or categorical image. If A has more than two dimensions, then imresize only resizes the first two dimensions. If scale is between 0 and 1, then B is smaller than A .

Discover More ›

How can we resize the image answer? ›

Generally speaking, image resizing comes in two forms:

Making the image bigger (upscaling) by increasing the dimensions, adding or stretching pixels, or increasing the file size.
Making the image smaller (downscaling) by decreasing the dimensions, subtracting or contracting pixels, or decreasing the overall file size.

Feb 2, 2024

Know More ›

How do you increase the pixel size of an image in Matlab? ›

Resize the image, using the imresize function. In this example, you specify a magnification factor. To enlarge an image, specify a magnification factor greater than 1. magnificationFactor = 1.25; J = imresize(I,magnificationFactor);

Get More Info ›

What is the best way to resize an image? ›

Adobe Express comes with all the options you need to change your image's dimensions instantly. Crop an image, change the aspect ratio, scale it, or resize it to a preset or custom dimension. The Adobe Express image resizer lets you resize images effortlessly — and for free.

Learn More Now ›

How do I rescale an image intensity in MATLAB? ›

J = imadjust( I ) maps the intensity values in grayscale image I to new values in J . By default, imadjust saturates the bottom 1% and the top 1% of all pixel values. The function linearly maps pixel values between the saturation limits to values between 0 and 1.

Tell Me More ›

How do I adjust the size of an image? ›

How to Resize an Image?

Click on the "Select Image" button to select an image.
Enter a new target size for your image.
Click the "Resize Image" button to resize the image.

Read On ›

How can we resize an object answer? ›

Resize a picture, shape, text box, or other object

Select the object.
Hold down CTRL.
Move the mouse pointer over one of the handles and then click and drag the mouse.
Release the mouse button before you release CTRL.

How do I resize an image to a different size? ›

To scale an image to fit your desired dimensions:

Open Photoshop.
Click "Open" and select the image you want to scale.
Click on the Image tab, and select Image Size.
In this window, you can specify what you want the image size to be. ...
You will notice that there is a link icon between the height and the width.

More items...

Mar 14, 2023

Learn More Now ›

How to get image size in MATLAB? ›

You must use [height, width, colour_planes] = size(image); because images have 3 dimensions. The third dimension is the number of colour planes. If you don't need this value, you can substitute ~ to ignore it.

Show Me More ›

How to resize raster MATLAB? ›

Resize the raster using mapresize . Double the length and width of the raster by specifying the scale as 2. Use nearest neighbor interpolation by specifying the interpolation method as 'nearest' . [Z2,R2] = mapresize(Z,R,2,'nearest');

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How to enhance image quality in MATLAB? ›

Improve Image Resolution Using Bicubic Interpolation

A standard way to increase image resolution without deep learning is to use bicubic interpolation. Upscale the low-resolution image using bicubic interpolation so that the resulting high-resolution image is the same size as the reference image.

Get More Info Here ›

Can I resize a JPEG image? ›

In Windows, open your JPEG using Paint, click “Select All,” and adjust the height and width by percentage or pixel length. Then select “Save As” and choose “JPEG.” On Macs, open your JPEG in Preview, click “Tools” and “Adjust Size.” Adjust the height and width by percent or pixel length, click “o*k,” and click “Save.”

See Details ›

How do I crop an image size in MATLAB? ›

Crop Image by Specifying Crop Region

Icropped = imcrop( I , rect ) crops the image I according to the position and dimensions specified in the crop rectangle rect . The cropped image includes all pixels in the input image that are completely or partially enclosed by the rectangle.

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How do I resize an image code? ›

One of the simplest ways to resize an image in the HTML is using the height and width attributes on the img tag. These values specify the height and width of the image element. The values are set in px i.e. CSS pixels.

Get More Info ›

How do you size a figure in MATLAB? ›

Set Figure Size

Set the figure size by clicking File > Export Setup. Specify the desired dimensions in the Width and Height fields, for example 5-by-4 inches. The dimensions include the entire figure window except for the frame, title bar, menu bar, and any tool bars.

How do I resize an image keeping proportions? ›

If the Shift key is held down whilst moving the handle, then the proportions of the object will be preserved. For example, if I hold Shift and drag the bottom edge upwards to reduce the size by half, then the right edge will automatically move to the left to reduce the width of the object by the same amount.

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