Vector image generation method, image processing apparatus, and computer-readable storage medium for computer program

A method for generating a vector image in an image processing apparatus, the method comprising the steps of:

• extracting a character group including one or more characters that are included in an image,
• obtaining an inclination of the character group;
• obtaining apex pixels that form contours of each of the characters;
• obtaining, from a portion that is expressed by a single line segment among the contours of said each of the characters, an identical line segment candidate pixel group serving as a candidate for a pixel group of the apex pixels that are positioned on the single line segment;
• extracting, based on the inclination, the identical line segment candidate pixel group thus obtained as an identical line segment pixel group that is the pixel group of the apex pixels that are positioned on the single line segment;
• extracting, based on a position of each of the apex pixels of the identical line segment pixel group thus extracted, both-end pixels which are apex pixels located on both sides of the identical line segment pixel group from among the apex pixels of the identical line segment pixel group;
• approximating, by a line segment connecting between the both-end pixels thus extracted, a contour of the character in a portion corresponding to the both-end pixels;
• and
• approximating a portion among the contours of the character, excluding the portion that has been approximated by the line segment connecting between the both-end pixels, by a straight line or a curved line by performing an outlining process using apex pixels other than the apex pixels of the identical line segment pixel group.

An image processing apparatus that performs a process of converting an image from a raster format to a vector format, comprising:

• an inclination detection portion that obtains an inclination of a character included in the image;
• an apex pixel extraction portion that obtains apex pixels forming contours of the character;
• an identical line segment pixel candidate extractor that obtains, from a portion that is expressed by a single line segment among the contours of the character, an identical line segment candidate pixel group serving as a candidate for a pixel group of the apex pixels that are positioned on the single line segment;
• an identical line segment pixel extractor that extracts, based on the inclination obtained by the inclination detection portion, the identical line segment candidate pixel group obtained by the identical line segment pixel candidate extractor as an identical line segment pixel group that is the pixel group of the apex pixels that are positioned on the single line segment;
• a both-end pixel extraction portion that extracts, based on a position of each of the apex pixels of the identical line segment pixel group extracted by the identical line segment pixel extractor, both-end pixels which are apex pixels located on both sides of the identical line segment pixel group from among the apex pixels of the identical line segment pixel group;
• a first approximation portion that approximates, by a line segment connecting between the both-end pixels extracted by the both-end pixel extraction portion, a contour of the character in a portion corresponding to the both-end pixels;
• and
• a second approximation portion that approximates a portion among the contours of the character, excluding the portion that has been approximated by the line segment connecting between the both-end pixels, by a straight line or a curved line by performing an outlining process using apex pixels other than the apex pixels of the identical line segment pixel group.

A non-transitory computer-readable storage medium storing thereon a computer program executed by a computer that performs a process of converting an image from a raster format to a vector format, the computer program causing the computer to perform the steps of:

• obtaining an inclination of a character included in an image;
• obtaining apex pixels that form contours of the character;
• obtaining, from a portion that is expressed by a single line segment among the contours of the character, an identical line segment candidate pixel group serving as a candidate for a pixel group of the apex pixels that are positioned on the single line segment;
• extracting, based on the inclination, the identical line segment candidate pixel group thus obtained as an identical line segment pixel group that is the pixel group of the apex pixels that are positioned on the single line segment;
• extracting, based on a position of each of the apex pixels of the identical line segment pixel group thus extracted, both-end pixels which are apex pixels located on both sides of the identical line segment pixel group from among the apex pixels of the identical line segment pixel group;
• approximating, by a line segment connecting between the both-end pixels thus extracted, a contour of the character in a portion corresponding to the both-end pixels;
• and
• approximating a portion among the contours of the character, excluding the portion that has been approximated by the line segment connecting between the both-end pixels, by a straight line or a curved line by performing an outlining process using apex pixels other than the apex pixels of the identical line segment pixel group.