Compression and decompression method of image data

A method of applying either of a reversible compression and an irreversible compression to image data in response to a compressing instruction, the method comprising:

• a first process of dividing the image data into a plurality of blocks;
• a second process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series;
• a third process of applying a wavelet transform to the image data obtained by the second process;
• a fourth process of performing quantization of the image data after the wavelet transform;
• a fifth process of performing differential operation of the image data after the quantization;
• and
• a sixth process of performing coding of the image data after the differential operation, wherein
• the method responds when the compressing instruction indicates the irreversible compression for repeatedly applying the first process through sixth process to the same block so as to reduce an amount of the image data by the irreversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the irreversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, and wherein
• the method responds when the compressing instruction indicates the reversible compression for repeatedly applying the first process, second process, fifth process and sixth process to the same block with skipping the third process and fourth process so as to reduce an amount of the image data by the reversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the reversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method.

A decompression apparatus for decompressing image data which is provided in a compressed form together with indication of a scan method applied to the image data, which is compressed by a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, and a compressing process of compressing the arranged image data so as to reduce an amount of the image data of the block, wherein the scanning process and the compressing process are repeatedly applied to the same block with using different scan methods defining different patterns of linearly scanning the image data, then an optimum one of the different scan methods is selected, which succeeds in most reducing the amount of the image data, and the compressed image data arranged by the selected scan method is provided together with indication of the selected scan method, the apparatus comprising:

• a decompressing section that decompresses the image data by reversely performing the compressing process;
• a rearranging section that rearranges the series of the decompressed image data by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing section that collectively stores the restored blocks of the image data.

A decompression apparatus for decompressing image data which is provided in a compressed form together with indication of a scan method and a compressing instruction applied to the image data, which has been compressed by a compression method including a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, a transform process of applying a wavelet transform to the image data obtained by the scanning process, a quantizing process of performing quantization of the image data after the wavelet transform, a differential process of performing differential operation of the image data after the quantization, and a coding process of performing coding of the image data after the differential operation, wherein the compression method responds when the compressing instruction indicates an irreversible compression for repeatedly applying the dividing process, scanning process, transform process, quantizing process, differential process and coding process to the same block so as to reduce an amount of the image data by the irreversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the irreversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, and wherein the compression method responds when the compressing instruction indicates a reversible compression for repeatedly applying the dividing process, scanning process, differential process and coding process to the same block with skipping the transform process and quantizing process so as to reduce an amount of the image data by the reversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the reversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, the decompression apparatus comprising:

• a first decoding section that decodes the image data by reversely performing the coding applied to the compressed image data;
• an adding section that performs an adding operation on the decoded image data to remove the differential operation applied to the image data;
• a second decoding section, being operative when the compressing instruction indicates that the image data has been irreversibly compressed, for performing a reverse quantization and a reverse wavelet transform to the image data fed from the adding section so as to decompress the image data, and being operative when the compressing instruction indicates that the image data has been reversibly compressed, for applying no operation to the image data fed from the adding section;
• a rearranging section that rearranges the series of the image data fed from the second decoding section by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing section that stores each of the restored blocks to thereby obtain an expanded form of the compressed image data.

A decompression program recorded on a computer readable medium and executable in a decompression apparatus for decompressing image data which is provided in a compressed form together with indication of a scan method applied to the image data, which has been compressed by a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, and a compressing process of compressing the arranged image data so as to reduce an amount of the image data of the block, wherein the scanning process and the compressing process are repeatedly applied to the same block with using different scan methods defining different patterns of linearly scanning the image data, then an optimum one of the different scan methods is selected, which succeeds in most reducing the amount of the image data, and the compressed image data arranged by the selected scan method is provided together with indication of the selected scan method, the decompression program being executed to perform a decompression method comprising:

• a decompressing process for decompressing the image data by reversely performing the compressing process;
• a rearranging process for rearranging the series of the decompressed image data by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing process for collectively storing the restored blocks of the image data.

A decompression program recorded on a computer readable medium and executable in a decompression apparatus for decompressing image data which is provided in a compressed form together with indication of a scan method and a compressing instruction applied to the image data, which has been compressed by a compression method including a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, a transform process of applying a wavelet transform to the image data obtained by the scanning process, a quantizing process of performing quantization of the image data after the wavelet transform, a differential process of performing differential operation of the image data after the quantization, and a coding process of performing coding of the image data after the differential operation, wherein the compression method responds when the compressing instruction indicates an irreversible compression for repeatedly applying the dividing process, scanning process, transform process, quantizing process, differential process and coding process to the same block so as to reduce an amount of the image data by the irreversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the irreversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, and wherein the compression method responds when the compressing instruction indicates a reversible compression for repeatedly applying the dividing process, scanning process, differential process and coding process to the same block with skipping the transform process and quantizing process so as to reduce an amount of the image data by the reversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the reversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, the decompression program being executable to perform a decompression method comprising:

• a first decoding process for decoding the image data by reversely performing the coding applied to the compressed image data;
• an adding process for performing adding operation of the decoded image data to remove the differential operation applied to the image data;
• a second decoding process being commenced when the compressing instruction indicates that the image data has been irreversibly compressed for performing a reverse quantization and a reverse wavelet transform to the image data fed from the adding process so as to decompress the image data, and being commenced when the compressing instruction indicates that the image data has been reversibly compressed for applying no operation to the image data fed from the adding process;
• a rearranging process for rearranging the series of the image data fed from the second decoding process by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing process for storing each of the restored blocks to thereby obtain an expanded form of the compressed image data.

A decompression method for decompressing image data which is provided in a compressed form together with indication of a scan method applied to the image data, which has been compressed by a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan. method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, and a compressing process of compressing the arranged image data so as to reduce an amount of the image data of the block, wherein the scanning process and the compressing process are repeatedly applied to the same block with using different scan methods defining different patterns of linearly scanning the image data, then an optimum one of the different scan methods is selected, which succeeds in most reducing the amount of the image data, and the compressed image data arranged by the selected scan method is provided together with indication of the selected scan method, the decompression method comprising:

• a decompressing process for decompressing the image data by reversely performing the compressing process;
• a rearranging process for rearranging the series of the decompressed image data by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing process for collectively storing the restored blocks of the image data.

A decompression method for decompressing image data which is provided in a compressed form together with indication of a scan method and a compressing instruction applied to the image data, which has been compressed by a compression method including a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, a transform process of applying a wavelet transform to the image data obtained by the scanning process, a quantizing process of performing quantization of the image data after the wavelet transform, a differential process of performing differential operation of the image data after the quantization, and a coding process of performing coding of the image data after the differential operation, wherein the compression method responds when the compressing instruction indicates an irreversible compression for repeatedly applying the dividing process, scanning process, transform process, quantizing process, differential process and coding process to the same block so as to reduce an amount of the image data by the irreversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the irreversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, and wherein the compression method responds when the compressing instruction indicates a reversible compression for repeatedly applying the dividing process, scanning process, differential process and coding process to the same block with skipping the transform process and quantizing process so as to reduce an amount of the image data by the reversible compression while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the reversibly compressed image data after arrangement by the selected scan method together with indication of the selected scan method, the decompression method comprising:

• a first decoding process for decoding the image data by reversely performing the coding applied to the compressed image data;
• an adding process for performing adding operation of the decoded image data to remove the differential operation applied to the image data;
• a second decoding process being commenced when the compressing instruction indicates that the image data has been irreversibly compressed for performing a reverse quantization and a reverse wavelet transform to the image data fed from the adding process so as to decompress the image data, and being commenced when the compressing instruction indicates that the image data has been reversibly compressed for applying no operation to the image data fed from the adding process;
• a rearranging process for rearranging the series of the image data fed from the second decoding process by an order reverse to that defined by the selected scanning method so as to restore each of the blocks;
• and
• a storing process for storing each of the restored blocks to thereby obtain an expanded form of the compressed image data.

A method of compressing image data representing dots of an image, comprising:

• a first process of dividing the image data into a plurality of blocks, so that each block represents n×m dots arranged in rows and columns;
• a second process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data, such that the arranged image data represents a liner arrangement of dots;
• and
• a third process of applying a wavelet transform to the arranged image data representing the liner arrangement of dots and then compressing the arranged image data after applying the wavelet transform so as to reduce an amount of the image data of the block, wherein
• the second process and the third process are repeatedly applied to the same block using different scan methods defining different patterns of linearly scanning the image data, then an optimum one of the different scan methods is selected, which succeeds in most reducing the amount of the image data, and the compressed image data arranged by the selected scan method is outputted together with indication of the selected scan method.

A method of compressing image data representing dots of an image and having either of an RGB format or an index format, the method comprising:

• a first process of dividing the image data into a plurality of blocks, so that each block represents n×m dots arranged in rows and columns;
• a second process of linearly scanning the image data within the block by a given scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data, such that the arranged image data represents a liner arrangement of dots;
• a third process of applying a wavelet transform to the image data representing the linear arrangement of dots obtained by the second process;
• a fourth process of performing quantization of the image data after the wavelet transform;
• a fifth process of performing a differential operation on the image data after the quantization;
• and
• a sixth process of performing coding of the image data after the differential operation, wherein
• when the image data has the RGB format, the method repeatedly applies the first process through sixth process to the same block so as to reduce an amount of the image data while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and outputting the compressed image data after arrangement by the selected scan method together with indication of the selected scan method, and wherein
• when the image data has the index format, the method repeatedly applies the first process, second process, fifth process and sixth process to the same block with skipping the third process and fourth process so as to reduce an amount of the image data while using different scan methods defining different patterns of linearly scanning the image data, then selecting an optimum one of the different scan methods, which succeeds in most reducing the amount of the image data, and, outputting the compressed image data after arrangement by the selected scan method together with indication of the selected scan method.

A decompression apparatus for decompressing image data which represents dots of an image and which is provided in a compressed form together with indication of an optimal scan method capable of optimally reducing an amount of compressed image data and actually applied to the image data, which is compressed by a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by the optimal scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data, and a compressing process of applying a wavelet transform to the arranged image data and compressing the arranged image data after applying the wavelet transform so as to reduce an amount of the image data of the block, the apparatus comprising:

• a decompressing section that decompresses the image data having the compressed form and applies a reverse wavelet transform to the decompressed image data, so that the decompressed image data after the reverse wavelet transform represents a linear arrangement of dots;
• a rearranging section that rearranges the linear arrangement of dots by an order reverse to that defined by the optimal scanning method so as to restore each of the blocks, such that each block represents n×m dots arranged in rows and columns;
• and
• a storing section that collectively stores the restored blocks of the image data.

A decompression apparatus for decompressing image data which represents dots of an image and which is provided in a compressed form together with indication of an optimal scan method capable of optimally reducing an amount of compressed image data and indication of a format of the image data, which has been compressed by a compression method including a dividing process of dividing the image data into a plurality of blocks, a scanning process of linearly scanning the image data within the block by the optimal scan method defining a pattern of linearly scanning the image data of the block so as to arrange the image data in series, a transform process of applying a wavelet transform to the image data obtained by the scanning process, a quantizing process of performing quantization of the image data after the wavelet transform, a differential process of performing differential operation of the image data after the quantization, and a coding process of performing coding of the image data after the differential operation, the decompression apparatus comprising:

• a first decoding section that decodes. the image data by reversely performing the coding applied to the compressed image data;
• an adding section that performs adding operation of the decoded image data to remove the differential operation applied to the image data;
• a second decoding section being operative when the indication indicates that the image data has an RGB format for performing a reverse quantization and a reverse wavelet transform to the image data fed from the adding section so as to decompress the image data, so that the decompressed image data after the reverse wavelet transform represents a linear arrangement of dots, and being, operative when the indication indicates that the image data has an index format for applying no operation to the image data fed from the adding section;
• a rearranging section that rearranges the linear arrangement of dots fed from the second decoding section by an order reverse to that defined by the optimal scanning method so as to restore each of the blocks, such that each block represents n×m dots arranged in rows and columns;
• and
• a storing section that stores each of the restored blocks to thereby obtain an expanded form of the compressed image data.