The two key steps of image stitching are registration and fusion. The purpose of registration is to register the image into the same coordinate system according to the geometric motion mode. Fusion is to combine the image into a large stitching image after registration.
In the process of multiple images registration, the geometric motion models mainly are translation model, similarity model, affine model and perspective model.
Image translation model refers to the image displacement of the horizontal and vertical direction and only in these two dimensions, if the camera only has translational motion, you can use the translation model. Image similarity model refers to that the camera itself may has rotational motion in addition to the translational motion. At the same time, it can also be described by the zoom factor and multiplication motion in the presence of scene zoom, so that similarity model can be used when the image is likely to has translational motion, rotational motion, and zooming motion. Image affine model is a 6-parameter transformation model, that is, Image affine model has the general characteristic of parallel lines are transformed into parallel lines and finite point mapping to finite point, the specific performance can be the uniform scale transformation and the non-uniform scale transformation and the shear transformation of the uniform scale transformation coefficients in different directions, etc, it can be used to describe the translational motion, rotational motion and a small range of scaling and deformation. Image perspective model is a transformation model with eight parameters, which can be a perfect representation of all kinds of table changes, and it is the most accurate transformation model.
Image fusion technology can be divided into non-multi-resolution technology and multi-resolution technology. Non-multi-resolution technology mainly includes average method, hat function method, weighted average method and median filter method. Multi-resolution technology mainly includes gaussian pyramid, laplacian pyramid, contrast pyramid, gradient pyramid and wavelet.