EP0540173A2
Expired / Lapsed
EP
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Color separation in ink jet color graphics printing
Assignee: HP Inc
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Filing: 1992-09-29
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Granted: —
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Expires: 2012-09-29
Abstract
Abstract In liquid-ink color graphics printing, true black ink is preferred over composite black wherever possible, but poor print quality results from printing black ink too close to color ink, due to limitations in present ink chemistry. A method of processing color bit-map graphics data in a four-color liquid-ink printing system, so as to maximize use of black ink while maintaining a minimum spacing between black and color inks (FIGS. 2-4) is disclosed. The input data is stored in CMY bit-map color planes (54,56,58). Preliminarily, data representing composite black is moved from the color planes into a K plane (60) for printing by a true black pen. The data is examined (66) to detect any black ink within the minimum spacing from color ink. The examination is expedited by partitioning the data into blocks (FIG. 8A), and indicating each block as a color block, a black block, or a white block (FIG. 11). These indications are conveniently stored in a color table (62) and a black table (64), in which each block of data is represented by a single bit (FIGS. 8-9). Tests for black adjacent color are conducted at the block level, i.e. in the tables (FIGS. 15-17), rather than at the individual bit level. Where a black block is detected adjacent a color block, the spacing violation is corrected by moving the corresponding block of data from the K plane back into the color planes (166) for printing as composite black. After such correction, the data is rechecked (174) to detect any new violation(s) resulting from the correction. The process repeated until no minimum spacing violations are found.
Inventors
- 👤 Ronald J. Vaughn
- 👤 John R. Matthews
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 19:06
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/52; G; G06; G06K; G06K15/00; G06K15/02; G06K15/10; G06K15/102; G06K2215/00; G06K2215/0002; G06K2215/0062; G06K2215/0071; G06K2215/0082; G06K2215/0094
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
182 words
A method of processing bit-map color graphics data for improved color separation comprising the steps of: receiving a page of bit-map color graphics input data defining at least three (CMY) color planes (54,58,56); if the input data does not include a K (black) plane, defining a K plane having the same dimensions as the color planes (60) so that each location in the K plane corresponds to a respective location in the color planes; examining the color planes to detect composite black bits (52); moving detected composite black bits from the color planes into the K plane (52), thereby changing the composite black bits to black bits for printing by a source of black ink; examining the color planes and the K plane to detect black bits located within a predetermined minimum spacing from color bits (66); and moving detected black bits from the K plane back into the color planes (66), thereby changing said black bits back into composite black bits for printing by a source of color inks to avoid printing black ink within the minimum spacing from color ink.
Claim 2
Dependent Claim
193 words
A method according to claim 1 wherein the step of examining the color planes and the K plane includes the steps of: partitioning the color planes to define an array of blocks of color data; building a color table (62) having a series of bits, each color table bit corresponding to a respective one of the color plane blocks and indicating whether or not the corresponding color plane block is a color block (FIG. 11); partitioning the K plane in the same manner as said partitioning the color planes, to define an array of blocks of K plane data; building a black table (64) having a series of bits, each black table bit corresponding to a respective one of the K plane blocks and indicating whether or not the corresponding K plane block is a black block (FIG. 11); for each bit in the color table that indicates a color block, examining a predetermined set of bits in the black table located adjacent a corresponding bit in the black table (FIG. 15) to detect bits that indicate a black block; and identifying each such adjacent black table bit which indicates a black block.
Claim 3
Dependent Claim
104 words
A method according to claim 2 further comprising the steps of: for each identified black table bit, moving the corresponding block of data from the K plane into the color planes (166-FIG. 18); updating the color table (172) and updating the black table (170) to reflect said moving step, thereby defining new entries in the color table and in the black table; repeating said examining adjacent bits in the black table (174) to ensure that the new entries in the color table are not adjacent black bits; and repeating said moving, updating and examining and indentifying steps until no minimum spacing violations are detected.
Claim 4
Dependent Claim
142 words
A method according to claim 2 or 3 wherein building the color table and the black table includes, for each block in the page: initializing the color table to all zeros; initializing the black table to all zeros; and for each byte in the block (70,72); testing the corresponding bytes in the color planes to detect whether or not all the said bytes are equal to zero (74); if the said color plane bytes are not all equal to zero, testing the said color plane bytes to determine whether the byte is color or composite black (76); if the byte is composite black, moving the corresponding byte from the color planes into the K plane (78); and turning on a bit in the black table that corresponds to the current block (78), thereby indicating that the current block is a black block.
Claim 5
Dependent Claim
98 words
A method according to claim 2 further comprising the steps of: if the byte is color, turning on a bit in the color table that corresponds to the current block (84), thereby indicating that the current block is a color block; testing whether or not a composite black byte has been detected previously within the current block (86); and if a composite black byte had been detected previously, copying the K plane data from said previously detected byte back into the color planes and turning off a bit in the black table that corresponds to the current block.
Claim 6
Dependent Claim
145 words
A method according to claim 2 wherein said examining the set of adjacent bits in the black table includes: testing a corresponding black table byte to detect an indication of a black block to the left or right of the bit in the color table byte that indicates a color block, thereby detecting a black block adjacent the color block; testing a black table byte above the corresponding black table byte (146,148) to detect an indication of a black block above the bit in the color table byte that indicates a color block, thereby detecting a black block adjacent the color block; and testing a black table byte below the corresponding black table byte (152,154) to detect an indication of a black block below the bit in the color table byte that indicates a color block, thereby detecting a black block adjacent the color block.
Claim 7
Dependent Claim
72 words
A method according to claim 2 wherein examining adjacent bits in the black table includes: forming a neighbor byte for the current color table byte (98); logically ANDing the neighbor byte together with the corresponding byte in the black table (100) to form a mask; testing the mask for zero (102); if the mask is not equal to zero, indicating that there is a black block adjacent to a color block (120).
Claim 8
Dependent Claim
157 words
A method according to claim 2 further comprising: logically ANDing the current color table byte together with a predetermined binary constant having a leftmost bit turned on and testing the result for zero (104), thereby testing whether the leftmost bit of the color table byte is on; and if the leftmost bit of the color table byte is on, checking the rightmost bits of black table bytes to the left of the black table byte that corresponds to the color table byte (106-116); logically ANDing the color table byte together with a predetermined binary constant having a rightmost bit turned on and testing the result for zero (126), thereby testing whether the rightmost bit of the color table byte is on; and if the rightmost bit of the color table byte is on, checking the leftmost bits of black table bytes to the right of the black table byte that corresponds to the color table byte (128-138).
Claim 9
Dependent Claim
246 words
A method according to claim 8 wherein checking the rightmost bits of black table bytes includes the steps of: logically ANDing a black table byte above and to the left of the color table byte together with a predetermined binary constant having a rightmost bit turned on and testing the result for zero (106), thereby checking whether the rightmost bit of the said black table byte is on; if the rightmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (108); logically ANDing a black table byte to the left of the color table byte together with a predetermined binary constant having a rightmost bit turned on and testing the result for zero (110), thereby checking whether the rightmost bit of the said black table byte is on; if the rightmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (112); logically ANDing a black table byte below and to the left of the color table byte together with a predetermined binary constant having a rightmost bit turned on and testing the result for zero (114), thereby checking whether the rightmost bit of the said black table byte is on; and if the rightmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (116).
Claim 10
Dependent Claim
246 words
A method according to claim 8 wherein checking the leftmost bits of black table bytes includes the steps of: logically ANDing a black table byte above and to the right of the color table byte together with a predetermined binary constant having a leftmost bit turned on and testing the result for zero (128), thereby checking whether the leftmost bit of the said black table byte is on; if the leftmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (130); logically ANDing a black table byte to the right of the color table byte together with a predetermined binary constant having a leftmost bit turned on and testing the result for zero (132), thereby checking whether the leftmost bit of the said black table byte is on; if the leftmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (134); logically ANDing a black table byte below and to the right of the color table byte together with a predetermined binary constant having a leftmost bit turned on and testing the result for zero (136), thereby checking whether the leftmost bit of the said black table byte is on; and if the leftmost bit of the said black table byte is on, moving the corresponding block of data from the K plane into the color planes (138).
References Cited (Backward Citations)
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