Image processing apparatus for preventing occurrence of moire in a reconstructed image
AssigneeRicoh Company, Ltd.
InventorYoshimichi Kanda
Life of this patent
Estimating the term…
Abstract
An image processing apparatus for image compression and decompression in which occurrence of moire in a reconstructed image is eliminated. The apparatus includes an encoder part for encoding an image into a compressed image, and a decoder part for decoding the compressed image into a reconstructed image. The encoder part includes an input part, a predictive coder, a subtracter, an ADCT encoder and a code memory. The predictive coder and subtracter act to remove high-frequency components prior to the calculation of the DCT coefficients by the ADCT encoder, thereby preventing moire in the reconstructed image.
Claims9
An image processing apparatus for processing input image data including a plurality of blocks for image data compression and decompression, each block including respective data of a predetermined number of successive pixels, said image processing apparatus comprising:
- a) extraction means having:
- 1) an input for inputting the input image data,
- 2) a first output for outputting a first value when an absolute value of a difference between respective data of a current pixel and a previous pixel from among the successive pixels of each block in the input image data is not smaller than a predetermined threshold value, and for outputting a second value when the absolute value of the difference is smaller than the threshold value, and
- 3) a second outputs
- b) first coding means, coupled to said first output of said extraction means, for coding each said value output from said extraction means to transform the data of the successive pixels of each block into encoded image data, said encoded image data including first encoded image data produced from said first value and other encoded image data produced from said second value;
- c) subtraction means having;
- 1) a first input for inputting the input image data,
- 2) a second input coupled to said second output of said extraction means, and
- 3) an output for outputting second image data for each of the plurality of blocks of the input image data, said second image data being produced by subtracting a sum of each of said values output from said first output of said extraction means and a previous value of the previous pixel output from said first output of said extraction means, from the input image data, said sum being output from said second output of said extraction means;
- and
- d) second coding means, coupled to said output of said subtraction means, and including:
- 1) means for subjecting each block to a discrete cosine transform to convert the second image data output by said subtraction means into DCT coefficients, said DCT coefficients including no high-frequency components which are produced when the input image data is subject to a discrete cosine transform because the first image data have been subtracted from the second image data;
- and
- 2) means for quantizing the DCT coefficients by dividing the DCT coefficients by each of quantization factors of a quantization table, so that quantized adaptive discrete cosine transform (ADCT) coefficients are output for each of the plurality of blocks of the input image data.
An image processing apparatus for processing input image data including a plurality of blocks for image data compression and decompression, each block including respective data of a predetermined number of successive pixels, said successive pixels including a current pixel and a previous pixel, said image processing apparatus comprising:
- a) extraction means having:
- 1) an input for inputting the input image data,
- 2) a first output for outputting first image data from the input image data, said first image data including high-frequency components which are produced when the input image data is subjected to a discrete cosine transform, and
- 3) a second output;
- b) first coding means, coupled to said first output of said extraction means, for coding said first image data output from said extraction means, so that encoded image data are produced from the first image data for each of the plurality of blocks of the input image data;
- c) subtraction means having:
- 1) a first input for inputting the input image data,
- 2) a second input coupled to said second output of said extraction means, and
- 3) an output for outputting second image data for each of the plurality of blocks of the input image data, said second image data being produced by subtracting a sum of each of the first image data output from said first output of said extraction means and a previous value of the previous pixel output from said first output of said extraction means, from the input image data, said sum being output from said second output of said extraction means;
- and
- d) second coding means, coupled to said output of said subtractions means, and including:
- 1) means for subjecting each block to a discrete cosine transform to convert the second image data output from said subtraction means into discrete cosine transform (DCT) coefficients, said DCT coefficients including no high-frequency components which are produced when the input image data is subjected to a discrete cosine transform;
- and
- 2) means for quantizing the DCT coefficients by dividing the DCT coefficients by each of the quantization factors of a quantization table, so that quantized adaptive discrete cosine transform (ADCT) coefficients are output for each of the plurality of blocks of the input image data.
Dependencies are inferred from the claim text.