Apparatus and method for assisting composition of photographic image

1. A photographing apparatus comprising:

an auxiliary line display unit that displays auxiliary lines comprising at least one of at least one vertical line movable in a horizontal direction within a screen and at least one horizontal line movable in a vertical direction within the screen;

an edge extracting unit that extracts an edge of an object image from image data obtained by photographing an object;

a straight line detecting unit that detects at least one straight line portion from the extracted edge;

a target extracting unit that extracts a target straight line portion from the detected at least one straight line portion, according to at least one of an inclination and a length of the detected at least one straight line portion; and

a distance calculating unit that calculates a distance between the extracted target straight line portion and at least one of the vertical line and the horizontal line,

wherein the auxiliary line display unit moves at least one of the vertical line and the horizontal line towards the target straight line portion based on the calculated distance between the target straight line portion and the at least one of the vertical line and the horizontal line.

2. The photographing apparatus of claim 1 , wherein the auxiliary line display unit displays the at least one of the vertical line and the horizontal line while moving the at least one of the vertical line and the horizontal line based on the calculated distance between the target straight line portion and the at least one of the vertical line and the horizontal line.

3. The photographing apparatus of claim 1 , further comprising a mode determining unit that determines whether the photographing apparatus is in an auxiliary line display mode where at least one of the vertical line and the horizontal line is displayed within the screen,

wherein the auxiliary line display unit displays the at least one of the vertical line and the horizontal line within the screen if the mode determining unit determines that the photographing apparatus is in the auxiliary line display mode, and does not display the at least one of the vertical line and the horizontal line if the mode determining unit determines that the photographing apparatus is not in the auxiliary line display mode.

4. The photographing apparatus of claim 1 , wherein the target extracting unit extracts a straight line portion having the largest length among the detected at least one straight line portion as the target straight line portion.

5. The photographing apparatus of claim 1 , wherein the target extracting unit extracts a straight line portion having the smallest inclination with respect to the horizontal line or the vertical line among the detected at least one straight line portion as the target straight line portion.

6. The photographing apparatus of claim 1 , wherein the target extracting unit extracts a straight line portion having the smallest distance from a center of the screen among the detected at least one straight line portion as the target straight line portion.

7. The photographing apparatus of claim 1 , wherein if the target extracting unit cannot extract the target straight line portion,

the distance calculating unit calculates a distance between a center of the screen and the vertical line or the horizontal line, and

the auxiliary line display unit displays the vertical line or the horizontal line while moving the vertical line or the horizontal line toward the center of the screen based on the distance between the center of the screen and the vertical line or the horizontal line.

8. A photographing apparatus comprising:

an auxiliary line display unit that displays auxiliary lines comprising at least one of at least one vertical line movable in a horizontal direction within a screen and at least one horizontal line movable in a vertical direction within the screen;

an edge extracting unit that extracts an edge of an object image from image data obtained by photographing an object;

a straight line detecting unit that detects a plurality of straight line portions from the extracted edge;

a target extracting unit that extracts a target straight line portion from the plurality of detected straight line portions, according to inclinations and lengths of the plurality of detected straight line portions; and

a distance calculating unit that calculates a distance between the extracted target straight line portion and at least one of the vertical line and the horizontal line,

wherein the auxiliary line display unit displays the vertical line or the horizontal line while moving the vertical line or the horizontal line towards the target straight line portion based on the calculated distance between the target straight line portion and the vertical line or the horizontal line.

9. A photographing method comprising:

displaying on a screen of a photographic apparatus auxiliary lines comprising at least one of at least one vertical line movable in a horizontal direction within the screen and at least one horizontal line movable in a vertical direction within the screen;

extracting by a processor of said photographic apparatus an edge of an object image from image data obtained by photographing an object;

detecting by said processor at least one straight line portion from the extracted edge;

extracting by said processor a target straight line portion from the detected at least one straight line portion, according to at least one of an inclination and a length of the detected at least one straight line portion;

calculating by said processor a distance between the extracted target straight line portion and at least one of the vertical line and the horizontal line; and

moving by said processor at least one of the vertical line and the horizontal line on said screen towards the target straight line portion based on the calculated distance between the target straight line portion and the at least one of the vertical line and the horizontal line.

10. The photographing method of claim 9 , wherein the moving of the at least one of the vertical line and the horizontal line comprises displaying the at least one of the vertical line and the horizontal line while moving the at least one of the vertical line and the horizontal line based on the calculated distance between the target straight line portion and the at least one of the vertical line and the horizontal line.

11. The photographing method of claim 9 , further comprising determining whether the photographing apparatus is in an auxiliary line display mode where at least one of the vertical line and the horizontal line is displayed within the screen,

wherein the displaying of the auxiliary lines comprises displaying the at least one of the vertical line and the horizontal line within the screen if it is determined that a current mode is the auxiliary line display mode, and displaying neither the vertical line nor the horizontal line if the current mode is not the auxiliary line display mode.

12. The photographing method of claim 9 , wherein the extracting of the target straight line portion comprises extracting a straight line portion having the largest length among the detected at least one straight line portion as the target straight line portion.

13. The photographing method of claim 9 , wherein the extracting of the target straight line portion comprises extracting a straight line portion having the smallest inclination with respect to the horizontal line or the vertical line among the detected at least one straight line portion as the target straight line portion.

14. The photographing method of claim 9 , wherein the extracting of the target straight line portion comprises extracting a straight line portion having the smallest distance from a center of the screen among the detected at least one straight line portion as the target straight line portion.