Image processing apparatus and method

A color image processing apparatus for converting multi-tone image signals to binary image signals in reference to threshold levels arranged in matrix to form a threshold pattern and for processing the binary image signals with a plurality of colors, which apparatus comprises:

• a generating means for respectively generating the multi-tone image signals for each color in succession;
• a first memory means which stores a plurality of threshold patterns corresponding respectively to each color;
• a second memory means which as a high-speed access ability for storing one of the threshold patterns from said first memory means;
• a converting means for converting the multi-tone image signals to the binary image signals in reference to the threshold pattern in said second memory means, said converting means including a reading means for reading out the threshold pattern from said second memory means in accordance with a size of the threshold pattern stored in said second memory means;
• a selecting means for selecting one of the threshold patterns in the first memory means in accordance with the color of the multi-tone image signal to be converted by said converting means;
• and
• a storing means for storing the selected threshold pattern from the first memory means in the second memory means.

An image processing method for converting multi-tone image signals to binary image signals in reference to threshold levels arranged in matrix to form a threshold pattern, which method comprises the steps of:

• generating the multi-tone image signals respectively for each color in succession;
• selecting one of a plurality of threshold patterns which are stored in a first memory means;
• storing the selected threshold pattern from the first memory means in a second memory means which has a high-speed access ability;
• reading out the selected threshold pattern from the second memory means in accordance with a size of the selected threshold pattern;
• and
• converting the multi-tone image signals to the binary image signals in reference to the threshold pattern which is read out from the second memory means.

A color image processing method for converting multi-tone image signals to binary image signals in reference to threshold levels arranged in matrix to form a threshold pattern and for processing the binary image signals with a plurality of colors, which method comprises the steps of:

• generating the multi-tone image signals respectively for each color in succession;
• selecting one of a plurality of threshold patterns stored in a first memory means in accordance with the color of the multi-tone image signal to be processed, said threshold patterns corresponding respectively to each color;
• storing the selected threshold pattern from the first memory means in a second memory means which has a high-speed access ability;
• reading out the selected threshold pattern from the second memory means in accordance with a size of the selected threshold pattern;
• and
• converting the multi-tone image signals to the binary image signals in reference to the threshold pattern which is read out from the second memory means.

An image processing apparatus for converting multi-tone image signals to binary image signals in reference to a threshold pattern, comprising:

• a first memory which stores a plurality of threshold patterns different from each other;
• selecting means for selecting one of the threshold patterns stored in the first memory;
• a second memory which has a high-speed access ability;
• storing means for storing the threshold pattern selected by said selecting means in the second memory;
• and
• converting means for converting the multi-tone image signals to the binary image signals in reference to the threshold pattern stored in the second memory, said converting means including reading means for reading out the threshold pattern from the second memory in accordance with a size of the threshold pattern in the second memory.

A method of converting multi-tone image signals to binary image signals in reference to a threshold pattern, the steps comprising:

• providing a first memory which stores a plurality of threshold patterns different from each other;
• providing a second memory which has a high-speed access ability;
• selecting one of the threshold patterns stored in the first memory;
• storing the selected threshold pattern in the second memory;
• reading out the selected threshold pattern from the second memory in accordance with a size of the selected threshold pattern;
• and
• converting the multi-tone image signals to the binary image signals in reference to the selected threshold pattern read out from the second memory.

An image processing apparatus for converting multi-tone image signals to binary image signals in reference to a threshold pattern, comprising:

• scanning means for scanning an original and generating the multi-tone image signals;
• a non-volatile read-only memory which stores a plurality of threshold patterns different from each other;
• selecting means for selecting one of the threshold patterns stored in the read-only memory;
• a random access memory which has a high-speed access ability for storing the threshold pattern selected by said selecting means;
• first means for reading out the threshold pattern selected by said selecting means from the read-only memory and writing the same in the random access memory;
• second means for reading out the threshold pattern from the random access memory in accordance with a size of the threshold pattern in the random access memory;
• and
• means responsive to said second means for converting the multi-tone image signals to the binary image signals in reference to the threshold pattern stored in the random access memory.