Image processing apparatus for performing an edge correction process and digital copying machine comprising said image processing apparatus therefor

An image processing apparatus for performing an edge emphasis process for color-dissolved image signals of respective colors of respective pixels sequentially inputted, said apparatus comprising:

• an image sensor;
• means for causing said image sensor to scan an original color document so as to generate image signals denoting a density level of each color of the original document at respective image pixels of said image sensor;
• edge amount detecting means for calculating an edge amount of each color from a density level of each color of an image signal of a specified pixel predetermined among said image signals and the density levels of each color of peripheral pixels located at a predetermined distance from said specified pixel, and outputting a detection signal of each color having a level of said calculated edge amount;
• edge emphasis means for adding the density level of each color of said specified pixel to a product of said edge amount of each color of said detection signal outputted from said edge amount detecting means and a predetermined coefficient, thereby performing an edge emphasis process for said image signal of said specified pixel;
• and
• edge emphasis suppressing means for controlling said edge emphasis means to decrease said predetermined coefficient so that the value of said addition result of said edge emphasis means is fallen into a predetermined dynamic range of said image signals.

An image processing apparatus for performing an edge emphasis process for color-dissolved image signals of respective colors of respective pixels sequentially inputted, said apparatus comprising:

• an image sensor;
• means for causing said image sensor to scan an original color document so as to generate image signals denoting a density level of each color of the original document at respective image pixels of said image sensor;
• edge amount detecting means for calculating an edge amount of a change amount in density level of each color between a specified pixel and peripheral pixels of said specified pixel based on said image signals of said specified pixel and said peripheral pixels, and outputting a detection signal of each color having said edge amount;
• edge amount converting means for converting said edge amount of each color of said detection signal outputted from said edge amount detecting means into a converted edge amount of each color, so that said converted edge amount becomes zero when the absolute value of said edge amount of said detection signal is smaller than a predetermined first threshold value, said converted edge amount becomes a product of a predetermined positive coefficient and said edge amount of said detection signal when the absolute value of said edge amount of said detection signal is larger than a predetermined second threshold value which is larger than said first threshold value, and said converted edge amount increases depending on said edge amount of said detection signal when the absolute value of said edge amount of said detection signal is a value obtained between said first and second threshold values, said converted edge amount continuously changing when the absolute value of said edge amount of said detection signal is said first threshold value and when the absolute value of said edge amount of said detection signal is said second threshold value, said edge amount converting means outputting a conversion signal of each color having level of said converted edge amount;
• edge emphasis means for adding the density level of each color of said specified pixel to a product of said edge amount of each color of said conversion signal outputted from said edge amount converting means and a predetermined coefficient, thereby performing an edge emphasis process for said image signal of said specified pixel;
• and
• edge emphasis suppressing means for controlling said edge emphasis means to decrease said predetermined coefficient so that the value of said addition result of said edge emphasis means is fallen into a predetermined dynamic range of said image signals.