Method and apparatus for image processing

A method for quantizing input image data implemented in an image processing apparatus comprising a processor and a memory, the method comprising:

• the processor performing the steps of:
• a bit connection step of connecting a decimal portion of corrected image data of a preceding pixel output from a latch component, to input image data of a target pixel as lower bits of the image data of the target pixel, and outputting the bit-connected image data of the target pixel, wherein the bit-connected image data has an integer portion of the image data of the target pixel and the decimal portion of image data of the preceding pixel;
• a correction step of generating corrected image data of the target pixel by adding a correction value to the bit-connected image data of the target pixel;
• a latch step of latching, by the latch component, a decimal portion of the corrected image data generated by the correction component of the target pixel by splitting-off, prior to performing quantization of the corrected image data, the decimal portion of the corrected image data from an integer portion of the corrected image data, output by the correction step, the split-off and latched decimal portion to be connected to the image data of the next pixel by the bit connection step, wherein the latch component does not latch the integer portion of the corrected image data of the target pixel;
• a quantization step of receiving an integer portion of the corrected image data without receiving the decimal portion of the corrected image data of the target pixel, and quantizing the received integer portion of the corrected image data of the target pixel;
• an inverse quantizing step of inverse-quantizing the quantized integer portion of the corrected image data of the target pixel, and outputting an inverse-quantized data of the target pixel;
• a calculation step of outputting a quantization error of the target pixel based on a difference between the integer portion of the corrected image data of the target pixel and the inverse-quantized data of the target pixel;
• a storing step of storing the integer portion of the calculated quantization error regarding each of the pixels, the integer portion of the calculated quantization error not including the decimal portion;
• and
• an error diffusion step of generating a correction value by diffusing the quantization error stored in said buffer,
• wherein the correction value to be added to the bit-connected image data of the target pixel in said correction step is generated by said error diffusion step based on the calculated quantization errors of neighboring pixels of the target pixel stored in said buffer and diffusion coefficients being smaller than 1.0.

A non-transitory computer-readable storage medium on which is stored a computer-executable program for implementing a method for quantizing input image data executed by an image processing apparatus, the program comprising the steps of:

• a bit connection step of connecting a decimal portion of corrected image data of a preceding pixel output from a latch component, to input image data of a target pixel as lower bits of the image data of the target pixel, and outputting the bit-connected image data of the target pixel, wherein the bit-connected image data has an integer portion of the image data of the target pixel and the decimal portion of image data of the preceding pixel;
• a correction step of generating corrected image data of the target pixel by adding a correction value to the bit-connected image data of the target pixel;
• a latch step of latching, by the latch component, a decimal portion of the corrected image data generated by the correction component of the target pixel by splitting-off, prior to performing quantization of the corrected image data, the decimal portion of the corrected image data from an integer portion of the corrected image data, output by the correction step, the split-off and latched decimal portion to be connected to the image data of the next pixel by the bit connection step, wherein the latch component does not latch the integer portion of the corrected image data of the target pixel;
• a quantization step of receiving an integer portion of the corrected image data without receiving the decimal portion of the corrected image data of the target pixel, and quantizing the received integer portion of the corrected image data of the target pixel;
• an inverse quantizing step of inverse-quantizing the quantized integer portion of the corrected image data of the target pixel, and outputting an inverse-quantized data of the target pixel;
• a calculation step of outputting a quantization error of the target pixel based on a difference between the integer portion of the corrected image data of the target pixel and the inverse-quantized data of the target pixel;
• a storing step of storing the integer portion of the calculated quantization error regarding each of the pixels, the integer portion of the calculated quantization error not including the decimal portion;
• and
• an error diffusion step of generating a correction value by diffusing the quantization error stored in said buffer,
• wherein the correction value to be added to the bit-connected image data of the target pixel in said correction step is generated by said error diffusion step based on the calculated quantization errors of neighboring pixels of the target pixel stored in said buffer and diffusion coefficients being smaller than 1.0.