Method and apparatus for enhancing digital image quality

A digital image quality enhancing apparatus for performing image enhancement processing on image data comprising pixels having predetermined resolutions obtained by scanning a document, the apparatus having a color data conversion unit for converting incoming RGB data for a concerned pixel into brightness data Xij and chrominance data, a division unit for dividing the concerned pixel into a background area requiring contrast enhancement and an area other than the background area not requiring the contrast enhancement using the brightness data Xij, an enhancement unit for performing the contrast enhancement on the concerned pixel belonging to the background area, and a color data inverse conversion unit for inversely converting a Yij signal output from the enhancement unit after contrast enhancement and the chrominance data output from the color data conversion unit back into the RGB data, wherein the division unit comprises:

• a mediator signal detecting portion which detects a minimum value of the brightness data Xij from a corresponding concerned line and outputs a mediator signal Vb while detecting a maximum value of the brightness data Xij from the corresponding concerned line and outputting a mediator signal Vp;
• a reference signal generating portion which outputs a signal X1 derived by applying a predetermined weighting factor α and a predetermined offset a to the mediator signal Vb in response to the mediator signal Vb while outputting a signal X2 derived by applying a predetermined weighting factor β and a predetermined offset b to the mediator signal Vp in response to the mediator signal Vp;
• and
• an area segmenting portion that compares the brightness data Xij with the signals X1 and X2 and outputs a first area signal if Xij is less than or equal to the signal X1, a second area signal if Xij is greater than the signal X1 but less than the signal X2, and a third area signal if Xij is greater than or equal to the signal X2.

A method of enhancing digital image quality, comprising:

• converting input color data for a concerned pixel into an input brightness component and input chrominance component;
• comparing a value of the input brightness component with first and second predetermined values, the second predetermined value being greater than the first predetermined value;
• outputting a brightness component having one of a lower value, a higher value, and the input value, in response to the comparison, wherein the outputting of the brightness component comprises:
• outputting the brightness component having the lower value in response to the comparison determining that the input brightness component in less than or equal to the first predetermined value,
• outputting the brightness component having the higher value in response to the comparison determining that the input brightness component is greater than or equal to the second predetermined value, and
• outputting the brightness component having the input value in response to the comparison determining that the input brightness component is neither less than or equal to the first predetermined value nor greater than or equal to the second predetermined value;
• re-converting the input chrominance component and the output brightness component to provide contrast enhanced color data for the concerned pixel;
• repeating the converting, the comparing, the outputting and the re-converting for each pixel in each concerned line;
• and
• updating the first and second predetermined values between concerned lines.