EP1073260A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Image processing device, image forming device incorporating the same, and storage medium for storing program used thereby
Assignee: Sharp Corp
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Filing: 2000-07-25
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Granted: —
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Expires: 2020-07-25
Abstract
Abstract Corrected values C1, M1, and Y1 corrected in a quasi-grayscale processing section of an image forming device by an error diffusion technique performed for each channel are evaluated in threshold value sections provided for individual channels, so as to determine whether or not they are greater than threshold values. If an overlapping CMY dot formation detector section detects that the density is higher than the threshold value in all of the three channels, a minimum density channel identifying section instructs a first quantized value substitution section and varies the outputs from the threshold value sections, so that the output in the channel with the lowest density has a value that does not represent dot formation. As a result, overlapping dot formation for the three channels is interrupted. Consequently, an image processing device capable of restraining occurrence of dark blotches and decrease in saturation can be offered without losing dot balance between channels even when a quasi-grayscale process is executed for each channel.
Inventors
- 👤 Yoshio Mizuyama
- 👤 Michiyuki Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 12:45
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/52
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
146 words
An image processing device (4, 4a to 4t),
including data output means (24c, 24m, 24y, 24Bk) for
providing output data representative of an image
constituted by pixels formed by a dot, overlapping dots,
or no formation of dots at all in predetermined channels
including channels for a plurality of hues, being characterised in that it comprises: first comparison means (31c, 31m, 31y, 31Bk, 61c,
61m, 61y, 61Bk) for comparing a density in each of the
hue channels with a predetermined threshold value for
each pixel constituting a colour input image; and dark blotch prevention means (34, 64) for adjusting
the output data so as to reduce the density in at least
one of the channels with densities higher than the
threshold values if the density is higher than the
threshold value at least in a predetermined number of
channels for a target pixel in the comparison.
Claim 2
Dependent Claim
70 words
The image processing device (4, 4a to 4k) as set
forth in claim 1, being characterised in that the predetermined channels include cyan, magenta,
and yellow channels, and the dark blotch prevention means (34) adjusts the
output data so as to reduce the density in one of the
three channels if the density is higher than the
threshold value in all of the three channels of cyan,
magenta, and yellow.
Claim 3
Dependent Claim
41 words
The image processing device (4, 4a to 4k) as set
forth in claim 2, being characterised in that the dark blotch prevention means (34) selects a
channel with a minimum density as the one channel in
which the density is reduced.
Claim 4
Dependent Claim
94 words
The image processing device (4f) as set forth in
either one of claims 2 and 3, being characterised in that said device further comprises second comparator
means (36c, 36m, 36y) for comparing an input to the first
comparison means (31c, 31m, 31y) for each channel with an
allowable value for density specified to be higher than
the threshold value for the first comparison means (31c,
31m, 31y), and the dark blotch prevention means (34) stops
adjusting the output data if the density is higher than
the allowable value in all of the three channels.
Claim 5
Dependent Claim
71 words
The image processing device (4a, 4c) as set forth
in any one of claims 1, 2, 3 and 4, being characterised
in that, said device further comprises brightness evaluation
means (35a, 41) for comparing brightness of the target
pixel with a predetermined brightness threshold value,
and the dark blotch prevention means (34) stops
adjusting the output data if the brightness of the target
pixel is lower than the brightness threshold value.
Claim 6
Dependent Claim
116 words
The image processing device (4m to 4p, 4r to 4t)
as set forth in claim 1, being characterised in that said device further comprises brightness evaluation
means (51) for comparing brightness of the target pixel
with a predetermined brightness threshold value, the predetermined channels includes cyan, magenta,
and yellow channels, and the dark blotch prevention means (64), if both the
density is higher than the threshold value in two or more
of the three channels of cyan, magenta, and yellow, and
the brightness is higher than the threshold value,
selects one of the channels with densities higher than
the threshold values and adjusts the output data so as to
reduce the densities in the remaining channels.
Claim 7
Dependent Claim
33 words
The image processing device (4m to 4p, 4r to 4t)
as set forth in claim 6, being characterised in that the dark blotch prevention means (64) selects a
channel with a maximum density.
Claim 8
Dependent Claim
96 words
The image processing device (4r) as set forth in
either one of claims 6 and 7, being characterised in that said device further comprises second comparator
means (67c, 67m, 67y) for comparing an input to the first
comparison means (61c, 61m, 61y) for each channel with an
allowable value for density specified to be higher than
the threshold value for the first comparison means (61c,
61m, 61y), and the dark blotch prevention means (64) stops
adjusting the output data if the density is higher than
the allowable value in two or more of the three channels.
Claim 9
Dependent Claim
51 words
The image processing device (4a, 4c, 4m to 4t) as
set forth In any one of claims 5, 6, 7, and 8, being
characterised in that the brightness threshold value for the brightness
evaluation means (35a, 41, 51) is a random value for
which a predetermined value serves as a reference.
Claim 10
Dependent Claim
73 words
The image processing device (4b, 4c, 4n) as set
forth in any one of claims 1 through 9, being
characterised in that said device further comprises saturation evaluation
means (35b, 42, 65n) for comparing a saturation of the
target pixel with a predetermined saturation threshold
value, and the dark blotch prevention means (34, 64) stops
adjusting the output data if the saturation of the target
pixel is lower than the saturation threshold value.
Claim 11
Dependent Claim
42 words
The image processing device (4b, 4c, 4n) as set
forth in claim 10, being characterised in that the saturation threshold value for the saturation
evaluation means (35b, 42, 65n) is a random value for
which a predetermined value serves as a reference.
Claim 12
Dependent Claim
74 words
The image processing device (4d, 4e, 4o, 4p) as
set forth in any one of claims 1 through 11, being
characterised in that said device further comprises area evaluation means
(35d, 44, 65o, 65p) for evaluating whether or not the
target pixel belongs to a text area according to the
input image, and the dark blotch prevention means (34, 64) stops
adjusting the output data if the target pixel belongs to
a text area.
Claim 13
Dependent Claim
72 words
The image processing device (4e, 4p) as set
forth in any one of claims 1 through 11, being
characterised in that said device further comprises area evaluation means
(44, 65p) for evaluating whether or not the target pixel
belongs to an unsaturated text area according to the
input image, and the dark blotch prevention means (34, 64) stops
adjusting the output data if the target pixel belongs to
an unsaturated text area.
Claim 14
Dependent Claim
31 words
The image processing device (4g, 4h, 4k, 4s, 4t)
as set forth in any one of claims 1 through 13, being
characterised in that the predetermined channels include a black channel.
Claim 15
Dependent Claim
56 words
The image processing device (4g, 4h, 4s) as set
forth in claim 14, being characterised in that said device further comprises output data adjusting
means (40, 72) for adjusting the output data so as to, if
the density is higher than a predetermined threshold
value in the black channel, reduce the densities in the
other channels.
Claim 16
Dependent Claim
67 words
The image processing device (4h) as set forth in
either one of claims 14 and 15, being characterised in
that said device further comprises evaluation means (47,
48) for evaluating whether a black dot has been formed in
proximity to the target pixel, and the dark blotch prevention means (34, 64) stops
adjusting the output data if a black dot exists in
proximity to the target pixel.
Claim 17
Dependent Claim
84 words
The image processing device (4k 4t) as set forth
in either one of claims 14, 15, and 16, being
characterised in that the predetermined channels include three channels of
cyan, magenta, and yellow, and said device further comprises black dot substitution
means (27) for adjusting the output data so as to, if the
output data represents overlapping formation of dots in
the three channels, instruct formation of a dot in the
black channel instead of the overlapping formation of
dots in the three channels.
Claim 18
Dependent Claim
67 words
The image processing device (4, 4a to 4t) as set
forth in any one of claims 1 through 17, being
characterised in that said device further comprises quasi-greyscale
processing means (4, 4a to 4t) for performing a quasi-greyscale
process for each of the predetermined channels
according to the input image and inputting a result to
the first comparison means (31c, 31m, 31y, 31Bk, 61c,
61m, 61y, 61Bk).
Claim 19
Dependent Claim
69 words
The image processing device (4, 4a to 4t) as set
forth in claim 18, being characterised in that the quasi-greyscale processing means (4, 4a to 4t)
includes error addition means (22) for adding up errors
of each channel density of the input image and each
channel density contained in the output data in the
quasi-greyscale process with a pixel in proximity to the
target pixel as a target pixel.
Claim 20
Dependent Claim
70 words
The image processing device (4g, 4h, 4k, 4s, 4t)
as set forth in either one of claims 18 and 19, being
characterised in that the predetermined channels include the black
channel, and said device further comprises saturated black
generation processing means (5g) for determining a
density in the black channel by a saturated black
generation method before the quasi-greyscale processing
means (4g, 4h, 4k, 4s, 4t) performs the quasi-greyscale
process.
Claim 21
Dependent Claim
65 words
The image processing device (4, 4a to 4t) as set
forth in any one of claims 1 through 20, being
characterised in that the data output means (24c, 24m, 24y, 24Bk) outputs
the output data to a colour image forming device (2, 2g)
including dot formation means (3c, 3m, 3y, 3Bk) that can
form dots for the channels overlapping one another on a
printing material.
Claim 22
Dependent Claim
53 words
The image processing device (4, 4a to 4t) as set
forth in claim 21, being characterised in that the dark blotch prevention means (34, 64) adjusts
the output data so that the dot formation means (3c, 3m,
3y, 3Bk) does not form a dot in the channel in which the
density is reduced.
Claim 23
Dependent Claim
75 words
An image forming device (1, 1a to 1t), being
characterised in that it comprises: the image processing device (4, 4a to 4t) as set
forth in any one of claims 1 through 21; and dot formation means (3c, 3m, 3y, 3Bk) capable of
forming a dot in a channel on top of another dot in
another channel on a printing material according to the
output data from the image processing device (4, 4a to
4t).
Claim 24
Dependent Claim
147 words
A storage medium for storing a program for
providing output data representative of an image
constituted by pixels each formed by a dot, overlapping
dots, or no formation of dots at all in predetermined
channels including channels for a plurality of hues, being characterised in that it stores a program that
runs a computer so as to serve as: first comparison means
(31c, 31m, 31y, 31Bk, 61c, 61m, 61y, 61Bk) for comparing
a density in each hue channel with a predetermined
threshold value for each pixel constituting a colour
input image; and dark blotch prevention means (34, 64)
for adjusting the output data so as to reduce the density
in at least one of the channels with densities higher
than the threshold values if the density is higher than
the threshold value at least in a predetermined number of
channels for a target pixel in the comparison.
References Cited (Backward Citations)
JPH1081026A
Cited
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