Projector and projection method

The invention provides a projector and a projection method. The projector comprises a control device, a projection light machine, a distance sensing device and an image capturing device. The control device outputs first image data. The projection light machine projects a first projection picture to the projection surface according to the first image data. The distance sensing device senses a plurality of distance parameters of the projection area. The image acquisition device acquires a first acquisition picture including the first projection picture. The control device performs keystone correction operation and flatness correction operation on the first image data. The projection light machine projects a second projection picture to the projection surface according to the corrected first image data. The control device obtains a second captured image including the second projection image through the image capturing device, and analyzes the second captured image to project the size information of the current p