Image processing method and apparatus

An image processing apparatus comprising:

• detecting means for detecting a level of a predetermined spatial frequency, said predetermined spatial frequency corresponding to portions in an image signal which portions have a feature selected from the group consisting of character and line drawing, said detecting means outputting a detection signal corresponding to the level of said predetermined spatial frequency;
• smoothing means for smoothing said image signal to produce a smoothed image signal;
• edge emphasizing means for edge-emphasizing said image signal to produce an edge-emphasized image signal;
• and
• mixing means for mixing said smoothed image signal and said edge-emphasized image signal,
• wherein a mixture ratio of said smoothed image signal and said edge-emphasized image signal is controlled in response to said detection signal, and a component of said smoothed image signal becomes larger when said detection signal becomes smaller, and
• wherein said mixture ratio is determined by an output of a continuous function using the level detected by said detecting means as a variable.

An image processing apparatus comprising:

• detecting means for detecting a level of a predetermined spatial frequency, said predetermined spatial frequency corresponding to portions in an image signal which portions have a feature selected from the group consisting of character and line drawing, said detecting means outputting a detection signal corresponding to the level of said predetermined spatial frequency;
• a smoothing circuit for smoothing said image signal to produce a smoothed image signal;
• mixing means for mixing said image signal and said smoothed image signal;
• and
• converting means for non-linearly converting said detection signal to produce a converted detection signal,
• wherein a mixture ratio of said mixing means is varied in response to said converted detection signal, and a component of said smoothed image signal becomes larger when said detection signal becomes smaller, and
• wherein said mixture ratio is determined by an output of a continuous function using the level detected by said detecting means as a variable.

An image processing apparatus comprising:

• detecting means for detecting a level of a predetermined spatial frequency, said predetermined spatial frequency corresponding to portions in an image signal which portions have a feature selected from the group consisting of character and line drawing, said detecting means outputting a detection signal corresponding to the level of said predetermined spatial frequency;
• a smoothing circuit for smoothing said image signal to produce a smoothed image signal;
• an edge emphasizing circuit for emphasizing the edges of said image signal to produce an edge-emphasized image signal;
• and
• converting means for non-linearly converting said detection signal to produce a converted detection signal,
• wherein said smoothed image signal and said edge-emphasized image signal are mixed, in a mixture ratio controlled in response to said detection signal, and said smoothed image circuit becomes larger when said detection signal become smaller, and
• wherein said mixture ratio is determined by an output of a continuous function using the level detected by said detecting means as a variable.

An image processing apparatus comprising:

• edge detecting means for detecting an edge portion of an image signal and outputting a detection signal;
• a smoothing circuit for smoothing said image signal to produce a smoothed image signal;
• an edge emphasizing circuit for emphasizing edges in said image signal to produce an edge-emphasized image signal;
• and
• means for mixing said smoothed image signal and said edge-emphasized image signal to produce a mixed signal or selecting said smoothed image signal in response to the detection signal and then outputting said mixed signal or selected signal,
• wherein said edge emphasizing circuit comprises a spatial filter having a peak frequency higher than a peak frequency of said edge detecting means.

An image processing apparatus comprising:

• edge detecting means for detecting an edge portion of an image signal and outputting a detection signal;
• a smoothing circuit for smoothing said image signal to produce a smoothed image signal;
• an edge emphasizing circuit for emphasizing edges in said image signal to produce an edge-emphasized image signal;
• and
• means for mixing said smoothed image signal said edge-emphasized image signal to produce a mixed signal or selecting said smoothed image signal in response to the detection signal and then outputting said mixed signal or selected output,
• wherein said edge detecting means comprises a spatial filter having a peak frequency lower than a primary harmonic frequency of a mesh image.

An image processing apparatus comprising:

• edge detecting means for detecting an edge portion of an image signal to produce a detection signal;
• a smoothing circuit for smoothing said image signal to produce a smoothed image signal;
• an edge emphasizing circuit for emphasizing edges in said image signal to produce an edge-emphasized image signal;
• and
• means for mixing said smoothed image signal and said edge-emphasized image signal to produce a mixed signal or selecting said smoothed image signal or said edge-emphasized image signal in response to the detection signal and then outputting said mixed signal or selected output,
• wherein said smoothing circuit comprises a spatial filter having a peak frequency characteristic near a primary harmonic frequency of a mesh image is sufficiently reduced.

An image processing method comprising the steps of:

• detecting a level of a predetermined spatial frequency corresponding to portions of character and line drawing in an input image signal, and outputting a detection signal corresponding to the level of the predetermined spatial frequency;
• smoothing said image signal to produce a smoothed image signal;
• mixing said image signal and the smoothed image signal to produce a mixed signal or selecting said image signal or the smoothed image signal and then outputting said mixed signal or the selected signal;
• and
• controlling a ratio of said mixture and said selection in response to the detection signal output in said detecting step,
• wherein a rate of a smoothed output in said smoothing step becomes larger when the detection signal becomes smaller, and
• wherein said ratio is determined by an output of a continuous function using the level detected in said detecting step as a variable.

An image processing method comprising the steps of:

• detecting a level of a predetermined spatial frequency corresponding to portions of character and line drawing in an input image signal and outputting a detection signal corresponding to the level of the predetermined spatial frequency;
• smoothing the image signal to produce a smoothed image signal;
• emphasizing the edge of the image signal to produce an edge-emphasized image signal;
• mixing the edge-emphasized image signal and the smoothed image signal to produce a mixed signal or selecting the edge-emphasized image signal or the smoothed image signal and then outputting the mixed signal or selected signal;
• and
• controlling a ratio of said mixture and said selection in response to the detection signal output in said detecting step,
• wherein an amount of a smoothed signal in said ratio becomes larger when the detection signal becomes smaller, and
• wherein said ratio is determined by a continuous function using the level detected in said detecting step as a variable.

An image signal processing apparatus comprising:

• input means for inputting an image signal;
• detection means for detecting a predetermined spatial frequency from the image signal to extract a character and line-drawing region, the predetermined spatial frequency corresponding to a character and a line drawing, said detection means producing a detection signal;
• smooth means for smoothing the image signal to produce a smoothed image signal;
• and
• edge emphasis means for edge-emphasizing the image signal to produce an edge-emphasized image signal,
• wherein said edge emphasis means is enabled in response to the detection signal, and
• wherein said smooth means is enabled with respect to lower and higher regions which regions are not detected by said detection means, said lower region representing a frequency region the frequency of which is lower than said predetermined spatial frequency, and said higher region representing a frequency region the frequency of which is higher than said predetermined spatial frequency.

An image signal processing apparatus comprising:

• receiving means for receiving a signal representing an image;
• detection means for detecting a spatial frequency in the image represented by the received signal;
• smoothing means for smoothing the received image signal to produce a smoothed image signal;
• edge-emphasis means for edge-emphasizing the received image signal to produce an edge-emphasized image signal;
• and
• forming means responsive to said detection means for forming an output signal at least predominantly from the edge-emphasized image signal for regions in the image having a spatial frequency within a predetermined frequency range and at least predominantly from the smoothed image signal for regions in the image having a spatial frequency outside the predetermined frequency range.

An image signal processing apparatus comprising:

• input means for inputting an image signal;
• detector means for detecting a predetermined local frequency range of the image signal corresponding to a character and a line drawing range for extracting the character and line drawing range;
• smoothing means for smoothing the image signal to produce a smoothed image signal;
• and
• edge-emphasis means for edge-emphasizing the image signal to produce an edge-emphasized image signal,
• wherein said edge-emphasis means is activated in the predetermined local frequency range in dependence on a detection result obtained by said detector means,
• wherein said smoothing means is active as a low-pass filter in at least a frequency range which is other than the predetermined local frequency range in dependence on the detection range of said detector means, and
• wherein said edge-emphasized image signal and said smoothed image signal are mixed in a mixer in a suitable ratio.

An image processing apparatus comprising:

• detecting means for detecting a level of feature of an input image signal;
• first processing means for processing the image signal;
• second processing means for processing the image signal, characteristics of said second processing means being different from characteristics of said first processing means;
• and
• mixing means for mixing an output of said first processing means and an output of said second processing means at a predetermined ratio,
• wherein said ratio is defined by an output of a continuous function using the level detected by said detecting means as a variable.