Method and apparatus for detecting edges in a mixed image

1. Field of the Invention A method and apparatus for detecting edges by which the detection of the edges of a natural image from an image obtained by mixing the graphic or text and the natural image is suppressed, to thereby stably detect edges of the graphic or the text, are disclosed. In this method, the differences in pixel value between the first pixel of sequentially input images and eight pixels adjacent to the first pixel are obtained. If all of the differences between the first pixel and the eight pixels adjacent to the first pixel are greater than a maximum threshold value or less than a minimum threshold value, the first pixel is determined to be an edge pixel. Likewise, determinations are made as to whether a second pixel, positioned adjacent the first pixel along a first dimension (for example to the left of the first pixel), is an edge pixel and whether a third pixel, positioned adjacent the first pixel along a second dimension (for example above the first pixel), is an edge pixel. Next, if at least one of the first pixel and the second pixel is determined as an edge pixel and if the difference between the first pixel and the second pixel is greater than the maximum threshold value, it is determined that the left edge of the first pixel exists. Also, if at least one of the first pixel and the third pixel is an edge pixel and the difference between the first pixel and the third pixel is greater than the maximum threshold value, it is determined that the upper edge of the first pixel exists.