Picture compression apparatus, picture reproducing apparatus and picture drawing apparatus

An apparatus for reproducing data obtained from a compressing device in which uncompressed digital image data having a plurality of bits is orthogonally transformed to produce coefficient data, said coefficient data is quantized to produce quantized data, said quantized data is decompressed to produce decompressed image data, said uncompressed digital image data is compared with said decompressed image data so as to detect any discrepancies therebetween and a control signal corresponding thereto is produced, said uncompressed digital image data is shifted by a number of bits in accordance with said control signal to produce shifted image data, and the quantized data is encoded, said compressing device being operative such that:

• (i) during a first iteration, if the comparison indicates an absence of said discrepancies then the quantized data corresponding to said uncompressed digital image data is encoded and if said comparison indicates a discrepancy then the quantized data corresponding to said uncompressed digital image data is not encoded and said uncompressed digital image data is bit shifted in accordance with said control signal, and (ii) during a second and any subsequent iterations, the shifted image data is orthogonally transformed, quantized, decompressed and compared so as to detect any discrepancies between the shifted image data and said uncompressed digital image data, whereupon if the comparison indicates an absence of said discrepancies then the quantized data corresponding to the current shifted image data is encoded and if said comparison detects a discrepancy then the quantized data corresponding to the current shifted image data is not encoded and said uncompressed digital image data is again shifted in accordance with the latest control signal, said apparatus comprising:
• dequantizer means for dequantizing the quantized data to produce recovered coefficient data;
• inverse transform means for inverse orthogonally transforming said recovered coefficient data to produce recovered shifted image data;
• and
• inverse shifting means for inverse shifting said recovered shifted image data in accordance with the number of bits shifted in said uncompressed digital image data as a function of the control signal to produce recovered decompressed image picture data.

A picture drawing apparatus for forming picture data from recorded data which is compressed by a compressing device wherein uncompressed digital image data having a plurality of bits is orthogonally transformed to produce coefficient data, said coefficient data is quantized to produce quantized data, said quantized data is decompressed to produce decompressed image data, said uncompressed digital image data is compared with said decompressed image data so as to detect any discrepancies therebetween and a control signal corresponding thereto is produced, said uncompressed digital image data is shifted by a number of bits in accordance with said control signal to produce shifted image data, and the quantized data is encoded, said compressing device being operative such that:

• (i) during a first iteration, if the comparison indicates an absence of said discrepancies then the quantized data corresponding to said uncompressed digital image data is encoded and if said comparison indicates a discrepancy then the quantized data corresponding to said uncompressed digital image data is not encoded and said uncompressed digital image data is bit shifted in accordance with said control signal, and (ii) during a second and any subsequent iterations, the shifted image data is orthogonally transformed, quantized, decompressed and compared so as to detect any discrepancies between the shifted image data and said uncompressed digital image data, whereupon if the comparison indicates an absence of said discrepancies then the quantized data corresponding to the current shifted image data is encoded and if said comparison detects a discrepancy then the quantized data corresponding to the current shifted image data is not encoded and said uncompressed digital image data is again shifted in accordance with the latest control signal, said apparatus comprising:
• reproducing means for reproducing the recorded encoded image data and shift data from a recording medium;
• decoding means including dequantizer means for dequantizing the reproduced encoded image data to produce recovered coefficient data, inverse transform means for inverse orthogonally transforming said recovered coefficient data to produce recovered shifted image data, rounding means for adding a value based on said shift data to said recovered shifted image data to produce rounded data and inverse shifting means for inverse shifting said rounded data as a function of said shift data to produce recovered decompressed image picture data;
• and
• drawing means for forming said recovered decompressed image picture data into said picture data for display by display means.