Method and apparatus for character string search in image

A method for searching at least one character string image in an image, comprising:

• providing a first image;
• detecting a character region in the first image based upon a shape thereof;
• extracting a first image feature of the character region, said first image feature containing image sub-features of a character string;
• receiving an input of a character string of interest by a user;
• generating a second image of said character string of interest;
• extracting a second image feature from the second image, said second image feature containing image sub-features of said character string of interest;
• comparing the first image feature with the second image feature to determine a level of similarity therebetween without breaking down the first and second image features per character into separate characters;
• and
• outputting the character region or the first image comprising the character region based on the level of similarity,
• wherein both the first image feature and the second image feature to be extracted are one-dimensional feature strings whose numbers of edges in a horizontal direction are obtained by binarizing luminance of each pixel and counting numbers of luminance changes in the character regions, when the character strings are arrayed vertically, and
• the step of determining a level of similarity involves elastic matching of the one-dimensional feature strings of the first image feature and the second image feature.

An apparatus for searching character string images in an image having separate characters, comprising:

• a means for providing a first image,
• a means for detecting a character region from the frame of the first image on the basis of its shape,
• a means for extracting a first image feature of the character region, said first image feature containing image sub-features of a character string,
• an input means for entering a desired character string by a user,
• a character image generating means for drawing a second image of the desired character string,
• a means extracting a second image feature from the second image, said second image feature containing image sub-features of said character string of interest,
• a feature matching means for matching the first image feature with the second image feature and determining a level of similarity therebetween without breaking down the first and second image features per character into separate characters, and
• an output means for outputting a matched character region or the first image comprising the matched character region,
• wherein said character region detecting means extracts equi-luminance pixel strings each of which has a length equal to or longer than a pre-designated length and has a luminance difference from a background within a pre-designated range.

An apparatus for searching character string images in an image having separate characters, comprising:

• a means for providing a first image,
• a means for detecting a character region from the frame of the first image on the basis of its shape,
• a means for extracting a first image feature of the character region, said first image feature containing image sub-features of a character string,
• an input means for entering a desired character string by a user,
• a character image generating means for drawing a second image of the desired character string,
• a means extracting a second image feature from the second image, said second image feature containing image sub-features of said character string of interest,
• a feature matching means for matching the first image feature with the second image feature and determining a level of similarity therebetween without breaking down the first and second image features per character into separate characters, and
• an output means for outputting a matched character region or the first image comprising the matched character region,
• wherein both the first image feature and the second image feature to be extracted are one-dimensional feature strings whose numbers of edges in a vertical direction are obtained by binarizing luminance of each pixel and counting numbers of luminance changes in the character regions, when the character strings are arrayed horizontally, and said feature matching means performs elastic matching of the one-dimensional feature strings both of which constitute the first image feature and the second image feature.

A program stored on a computer readable medium for processing of character search in an image having separate characters comprising:

• a module for providing a first image,
• a module for detecting a character region from the frame of the first image on the basis of its shape,
• a module for extracting a first image feature of the character region, said first image feature containing image sub-features of a character string,
• a module for receiving an input of a desired character string input by a user,
• a module for drawing a second image of the input character string,
• a module for extracting a second image feature from the second image, said second image feature containing image sub-features of said character string of interest,
• a module for matching the first image feature with the second image feature and determining a level of similarity therebetween without breaking down the first and second image features per character into separate characters,
• a module for outputting the character region containing the input character string in respect of which the level of similarity has been determined, and
• a module for removing line border blurring by correcting a border pixel luminance value into a maximum or minimum luminance value of adjacent pixels,
• wherein the module for detecting said character region includes extracting lines with a width in a specific range and extracting a concentrated region on the extracted lines as said character region.