Image registration is a fundamental technique used in image processing to align different images that are captured at different times, from different viewpoints, or with different imaging modalities. The goal of image registration is to establish a spatial correspondence between the corresponding image points, allowing for further analysis, comparison, and fusion of the images.

  The process of image registration typically involves several steps:

  1. Feature Extraction: This step involves identifying distinctive features in the images, such as corners, edges, or landmarks. Features should be robust and easily identifiable across different images.

  2. Feature Matching: The extracted features are then matched between the images to establish correspondences. Various techniques like intensity-based matching, correlation-based matching, or keypoint-based matching algorithms can be used for this purpose.

  3. Transform Estimation: Once the correspondences are established, a transformation model is computed to align the images. The model determines how one image needs to be transformed to match the other image. Common models include affine transformations, projective transformations, or non-linear deformations.

  4. Resampling: After estimating the transformation, resampling is performed to reposition the pixel intensities from one image to another. This involves warping the pixels of one image based on the estimated transformation parameters.

  5. Image Fusion: Following resampling, the aligned images can be fused to create a composite image that combines the information from all the registered images. This can be useful in applications like medical imaging, where combining multiple scans can provide a more comprehensive view of a patient's condition.

  Image registration finds applications in various fields, including medical imaging, remote sensing, computer vision, and augmented reality. It enables tasks such as image stitching, image mosaicking, change detection, object recognition, and image-guided interventions.

  Overall, image registration is a critical process that aligns images spatially, allowing for accurate analysis and comparison of different image data.