| 摘要 |
A method for detecting a linear boundary between image border and picture regions comprises identifying the position of the boundary as the position of a maximum pixel-value spatial-gradient parameter, measured in a direction perpendicular to the boundary. Also independently claimed is a similar method of detecting such a linear boundary comprising measuring a pixel value spatial gradient parameter for each of a set of candidate boundaries, measured perpendicular to the boundary, determining for each candidate boundary a measure of the size of a border region associated with that candidate boundary, and selecting from the possible, candidate boundaries based on the gradient and size parameters. Pixel values may be modified by a non-linear function 106 before determining the maximum gradient, for example having a maximum slope for a particular pixel value but rapidly decreasing otherwise. A constant value 104, based on image black level 103, may also be added to the image pixels, and modification based on distance from image edges may be performed 114. Pixel luminance, primary colour separation or colour difference values may be used. |
