warpAffine

Usage

Performs affine transformation on an image based on a given matrix and returns the transformed image. Affine transformation is two-dimensional and may include rotation, scaling, translation, and cropping.

Interface

void warpAffine(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags = INTER_LINEAR, int borderMode = BORDER_CONSTANT, const Scalar& borderValue = Scalar());

Parameters

Parameter	Description	Value Range	Input/Output
src	Input image.	Not null	Input
dst	Output image.	Mat class	Output
M	Affine transformation matrix.	2x3	Input
dsize	Size of the output image.	(-inf, inf)	Input
flags	Interpolation method.	INTER_NEAREST, INTER_LINEAR, INTER_CUBIC, and INTER_LANCZOS4	Input
borderMode	Border mode, which determines how to process image borders.	BORDER_CONSTANT, BORDER_REPLICATE, and BORDER_REFLECT	Input
borderValue	Constant used to populate borders.	(-inf, inf)	Input

Return Values

Success: KP_CV_SUCCESS
Failure: an error code

Error Codes

Error Code	Description
INVALID_PARAM_MSG	The input image is null.
NOT_SUPPORT_MSG	The input image type is incorrect or the flags value is not supported.

Example

#include <opencv2/opencv.hpp>
#include <iostream>

int main() {
    // Create a 5x5 image.
    cv::Mat src = (cv::Mat_<uint8_t>(5, 5) << 0, 0, 0, 0, 0,
                                              0, 1, 1, 1, 0,
                                              0, 1, 0, 1, 0,
                                              0, 1, 1, 1, 0,
                                              0, 0, 0, 0, 0);

    // Define the affine transformation matrix.
    cv::Mat M = (cv::Mat_<float>(2, 3) << 1, 0, 1,
                                          0, 1, 1);

    // Apply affine transformation.
    cv::Mat dst;
    cv::warpAffine(src, dst, M, cv::Size(5, 5), cv::INTER_LINEAR, cv::BORDER_CONSTANT, cv::Scalar(0));

    // Output image
    std::cout << std::endl << dst << std::endl;

    return 0;
}

Output:

[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 1 1 1]
 [0 0 1 0 1]
 [0 0 1 1 1]]

Parent topic: Interface Definition