Process and apparatus for image magnification

A process for determining values of new pixels which are to be interpolated in a unit area which is determined by four pixel centers of an original image on a display screen, and which has the four pixel centers at four corners thereof, respectively, for magnifying an image consisting of original pixels on the display screen, comprising the steps of:

• (a) storing, in a plurality of registers, coordinates of a set of division lines uniquely defining a plurality of modes of division of the unit area, respectively, wherein, in each of the modes, the unit area is divided into sections by one of the division lines corresponding to each of the modes;
• (b) detecting an angle of an original line image in a predetermined vicinity of the unit area by comparing values of a combination of original pixels in the predetermined vicinity of the unit area with each of a plurality of predetermined patterns of an arrangement of pixel values, where the detected angle is digitized to one of a plurality of original line angles;
• (c) selecting one of a plurality of predetermined modes of division of the unit area so that an angle of one of the division lines of the selected mode of division conforms to the original line angle detected in step (b);
• (d) determining a value for each of the new pixels by assigning a value, determined based on the values of the original pixels in the predetermined vicinity, to all of the new pixels having centers in one of the sections of the unit area generated by the mode of division selected in step (c);
• and
• (e) modifying the original image on the display screen to produce a picture image using the values of the original pixels and the values of the new pixels generated in steps (a)-(d),
• the plurality of original line angles including 0 degrees, 90 degrees, .+-.tan.sup.-1 1, .+-.tan.sup.-1 1/2, and .+-.tan.sup.-1 2,
• said selecting in step (c) selecting one of the plurality of predetermined modes of division including:
• a first mode having the division lines determined by x=0, y=0, x.+-.y=1/2, and x.+-.y=-1/2;
• a second mode having the division lines determined by x=0, y=0, x.+-.y/2=1/2, and x.+-.y/2=-1/2;
• a third mode having the division lines determined by x=0, y=0, x/2.+-.y=1/2, and x/2.+-.y=-1/2;
• a fourth mode having the division lines determined by x=0, y=0, and y=+2x.ltoreq.0;
• a fifth mode having the division lines determined by x=0, y=0, and y=-2x.gtoreq.0;
• a sixth mode having the division lines determined by x=0, y=0, and y=+2x.gtoreq.0;
• a seventh mode having the division lines determined by x=0, y=0, and y=-2x.ltoreq.0;
• an eighth mode having the division lines determined by x=0, y=0, and x=+2y.ltoreq.0;
• a ninth mode having the division lines determined by x=0, y=0, and x=-2y.ltoreq.0;
• a tenth mode having the division lines determined by x=0, y=0, and x=+2y.gtoreq.0;
• and
• an eleventh mode having the division lines determined by x=0, y=0, and x=-2y.gtoreq.0;
• x=0 corresponds to a vertical line, y=0 corresponding to a horizontal line, and x=.+-.1/2 and y=.+-.1/2 determine the boundary of the unit area.

A process for determining values of new pixels which are to be interpolated in a unit area which is determined by four pixel centers of an original image on a display screen, and which has the four pixel centers at four corners thereof, respectively, for magnifying an image consisting of original pixels on the display screen, comprising the steps of:

• (a) storing, in a plurality of registers, coordinates of a set of division lines uniquely defining a plurality of modes of division of the unit area, respectively, where, in each of the modes, the unit area is divided into sections by one of the division lines corresponding to each of the modes;
• (b) detecting an angle of an original line image in a predetermined vicinity of the unit area by comparing values of a combination of original pixels in the predetermined vicinity of the unit area with each of a plurality of predetermined patterns of an arrangement of pixel values, where the detected angle is digitized to one of a plurality of original line angles;
• (c) selecting one of a plurality of predetermined modes of division of the unit area so that an angle of one of the division lines of the selected mode of division conforms to the original line angle detected in step (b);
• (d) determining a value for each of the new pixels by assigning a value, determined based on the values of the original pixels in the predetermined vicinity, to all of the new pixels having centers in one of the sections of the unit area generated by the mode of division selected in step (c);
• (e) dividing the unit area into sub-areas corresponding to each of the original pixel centers surrounding the unit area so that all points in each sub-area are nearer to the original pixel center corresponding thereto than to any other of the original pixel centers;
• (f) determining each of the sub-areas having the center of at least one of the new pixels included therein, and
• the predetermined patterns and the combination of the original pixels used for the comparing in step (b) being defined for each of the sub-areas, and the predetermined modes of division being defined within each of the sub-areas;
• and
• (g) modifying the original image on the display screen to produce a picture image using the values of the original pixels and the values of the new pixels generated in steps (a)-(f).

An apparatus for determining values of new pixels to be interpolated in a unit area determined by four original pixel centers of an original image, the unit area having the four pixel centers at four corners thereof, for magnifying an image consisting of original pixels, said apparatus comprising:

• new pixel coordinate generating means for generating a coordinate of a center of a new pixel for interpolating between the original pixel centers according to a magnification rate;
• pattern detecting means for detecting one of a plurality of line images by comparing values of a combination of the original pixels in a predetermined vicinity of the unit area with each of a plurality of predetermined patterns;
• selector means for selecting one of a plurality of predetermined modes of division of the unit area according to the one of the line images detected in said pattern detecting means, the predetermined modes of division corresponding to the predetermined patterns, each of the predetermined modes of division dividing the unit area into sections by a set of division lines uniquely defined for each of the modes of division;
• section determining means for determining a section containing the center of the new pixel located by said new pixel coordinate generating means, in accordance with information of the division lines dividing the unit area in the mode of division selected in said selector means, such that the section is one of the sections generated by each of the modes of division so that each of the new pixels in the section has the same value determined by values of the original pixels in the predetermined vicinity;
• new pixel value calculating means for determining the value of the new pixel located by said new pixel coordinate generating means, according to the values of the original pixels in the predetermined vicinity and the section determined in said section determining means;
• nearest original pixel determining means for determining one of the original pixel centers surrounding the unit area as nearest to the new pixel, the predetermined patterns and the predetermined vicinity being predetermined for each of the pixels centers surrounding the unit area;
• and
• picture image data generating means for generating picture image data using the values of the original pixels and the value calculated for each of the new pixels.