A calibration method of projected image, which is suitable for calibrating deformation of the projected image being projected by an image projection apparatus, comprising steps of:
- displaying an original image data as a first image having a first boundary characteristic;
- projecting the first image as the projected image by using the image projection apparatus;
- analyzing a difference between a boundary shape of the projected image and the first boundary characteristic which is unadjusted;
- adjusting the first boundary characteristic according to the difference between the boundary shape of the projected image and the unadjusted first boundary characteristic until the boundary shape of the projected image is similar to the unadjusted first boundary characteristic;
- and
- recording the first boundary characteristic as a second boundary characteristic when the boundary shape of the projected image is similar to the unadjusted first boundary characteristic,
- wherein the first boundary characteristic is the shape of at least one displaying boundary line around the first image,
- wherein the step of analyzing the difference between the boundary shape of the projected image and the first boundary characteristic which is unadjusted comprises steps of:
- retrieving at least two original image reference points from a boundary data displayed as the at least one displaying boundary line forming the first boundary characteristic, wherein the boundary data is included in the original image data;
- setting an expected boundary of an expected projected image to be similar to the unadjusted first boundary characteristic;
- for each of the at least two original image reference points, estimating a displayed reference point position where a corresponded one of the at least two original image reference points is displayed while displaying the original image data as the first image having the first boundary characteristic;
- for each of the at least two original image reference points, estimating a projected reference point position in the projected image according to the displayed reference point position, wherein the corresponded one original image reference point is projected onto the projected reference point position;
- and
- for each of the at least two original image reference points, estimating a distance between the projected reference point position and the expected boundary, and recording the distance as a reference point shift value corresponding to the projected reference point position;
- wherein the step of adjusting the first boundary characteristic according to the difference between the boundary shape of the projected image and the unadjusted first boundary characteristic until the boundary shape of the projected image is similar to the unadjusted first boundary characteristic comprises steps of:
- determining whether each of the reference point shift values is not greater than a predetermined value;
- when any one of the reference point shift values is greater than the predetermined value,
- adjusting the first boundary characteristic existed currently;
- displaying the original image data as the first image having the first boundary characteristic existed currently;
- and
- projecting the first image by the image projection apparatus to obtain the projected image;
- and
- determining the boundary shape of the projected image is similar to the unadjusted first boundary characteristic when each of the reference point shift values is not greater than the predetermined value;
- wherein the step of adjusting the first boundary characteristic which exists currently comprises steps of:
- keeping positions of the original image reference points unchanged while adjusting at least one of the displayed reference point positions such that the adjusted displayed reference point position is closer to the expected boundary than before;
- selecting every two neighbored displayed reference point positions as a parameter for performing a Cubic Spline algorithm to obtain a Cubic Spline function between the selected two neighbored displayed reference point positions;
- and
- setting a set comprising every obtained Cubic Spline function to be the first boundary characteristic existed currently.