imrotate

Rotate image

Syntax

J = imrotate(I,angle)

J = imrotate(I,angle,method)

J = imrotate(I,angle,method,bbox)

Description

J = imrotate(I,angle) rotates image I by angle degrees in a counterclockwise direction around its center point. To rotate the image clockwise, specify a negative value for angle. imrotate makes the output image J large enough to contain the entire rotated image. By default, imrotate uses nearest neighbor interpolation, setting the values of pixels in J that are outside the rotated image to 0 for numeric and logical images and missing for categorical images.

J = imrotate(I,angle,method) rotates image I using the interpolation method specified by method.

J = imrotate(I,angle,method,bbox) also uses the bbox argument to define the size of the output image. You can crop the output to the same size as the input image or return the entire rotated image.

Examples

Rotate Image Clockwise for Better Horizontal Alignment

Read an image into the workspace, and convert it to a grayscale image.

I = fitsread('solarspectra.fts');
I = rescale(I);

Display the original image.

figure
imshow(I)
title('Original Image')

Rotate the image 1 degree clockwise to bring it into better horizontal alignment. The example specified bilinear interpolation and requests that the result be cropped to be the same size as the original image.

J = imrotate(I,-1,'bilinear','crop');

Display the rotated image.

figure
imshow(J)
title('Rotated Image')

Input Arguments

I — Image to be rotated

numeric array | logical array | categorical array

Image to be rotated, specified as a numeric array, logical array, or categorical array.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | categorical

angle — Amount of rotation in degrees

numeric scalar

Amount of rotation in degrees, specified as a numeric scalar.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical

method — Interpolation method

"nearest" (default) | "bilinear" | "bicubic"

Interpolation method, specified as one of the following values:

Value	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. Nearest-neighbor interpolation is the only method supported for categorical images.
"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.

Data Types: char | string

bbox — Bounding box defining size of output image

"loose" (default) | "crop"

Bounding box that defines the size of output image, specified as either of the following values:

Value	Description
"crop"	Make output image J the same size as the input image I, cropping the rotated image to fit.
"loose"	Make output image J large enough to contain the entire rotated image. J is larger than I.

Data Types: char | string

Output Arguments

J — Rotated image

numeric array | logical array | categorical array

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

Tips

• In some instances, this function takes advantage of hardware optimization for data types uint8, uint16, single, and double to run faster.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• imrotate supports the generation of C code (requires MATLAB^® Coder™). Note that if you choose the generic MATLAB Host Computer target platform, imrotate generates code that uses a precompiled, platform-specific shared library. Use of a shared library preserves performance optimizations but limits the target platforms for which code can be generated. For more information, see Types of Code Generation Support in Image Processing Toolbox.

• Input images of data type categorical are not supported.

• The method and bbox arguments must be compile-time constants.

GPU Code Generation

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

Usage notes and limitations:

• Input images of data type categorical are not supported.

• The method and bbox arguments must be compile-time constants.

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 must be of type uint8, uint16, single, or logical.

• The "bicubic" interpolation mode used in the GPU implementation of this function differs from the default (CPU) bicubic mode. The GPU and CPU versions of this function are expected to give slightly different results.

For more information, see Image Processing on a GPU.

Version History

Introduced before R2006a

R2021b: Support for thread-based environments

imrotate now supports thread-based environments.

R2015b: New spatial conventions

This function changed in version 9.3 (R2015b). Previous versions of the Image Processing Toolbox™ use different spatial conventions. If you need the same results produced by the previous implementation, use the function imrotate_old.