Image data compression method and apparatus with pre-processing to compensate for the blocky effect

A system for pre-processing image data to compensate for blocky effect error introduction thereto during subsequent block-basis image compression followed by decoding by application of an inverse transform, said system including:

• means for processing the image data to generate error-compensation data indicative of error likely to be introduced to said image data during said subsequent block-basis image compression followed by said decoding;
• and
• means for combining the error-compensation data with the image data to generate pre-processed image data which will exhibit reduced blocky effect error after application of said block-basis image compression and then said decoding thereto, wherein the means for processing the image data includes:
• means for generating delayed image data by delaying the image data for a first delay period;
• compression means for applying, during said first delay period, block-basis image compression to said image data to generate compressed data, then inverse quantizing the compressed data during said first delay period to generate dequantized data, and then applying, during said first delay period, said inverse transform to the dequantized data to generate processed data;
• and
• means for generating the error-compensation data by subtracting one of the delayed image data and the processed data from the other of the delayed image data and the processed data.

A system for pre-processing image data to compensate for blocky effect error introduction thereto during subsequent block-basis image compression followed by decoding by application of an inverse transform, said system including:

• means for processing the image data to generate error-compensation data indicative of error likely to be introduced to said image data during said subsequent block-basis image compression followed by said decoding;
• and
• means for combining the error-compensation data with the image data to generate pre-processed image data which will exhibit reduced blocky effect error after application of said block-basis image compression and then said decoding thereto, wherein the means for processing the image data includes:
• a first delay means for generating delayed image data by delaying the image data for a first delay period;
• a block-basis compression means connected in parallel with the first delay means, said block-basis compression means including a transform means which outputs transformed image data in response to said image data, a quantization means which outputs quantized image data in response to said transformed image data, an inverse quantization means which outputs dequantized image data in response to the quantized image data, and an inverse transform means which outputs inverse transformed image data in response to said dequantized image data;
• and
• a subtraction means for subtracting one of the delayed image data and the inverse transformed image data from the other of the delayed image data and the inverse transformed image data, thereby generating said error-compensation data.