Method of compressing digital image data and device thereof

An image data compression device having coding means, comprising:

• detection means connected to said coding means, for detecting first, second, third and fourth edge values respectively from a luminance signal, first and second chrominance signals and image blocks representative of a block format combination of said luminance signal and said first and second chrominance signals of said coding means;
• decision means for normalizing said first edge value to provide a quantization scaling factor;
• block bit allocation means for allocating a number of bits corresponding to said each image block according to said first, second, third and fourth edge values;
• and
• factor bit allocation means for subtracting a number of DC factor bits of each image block coded by a one-dimensional Huffman coding technique from a number of the block allocation bits allocated by said block bit allocation means to thereby allocate a number of AC factor bits.

A data compression device, comprising:

• means for receiving an image signal representative of a luminance signal and first and second color-difference signals, and for formatting said image signal into a plurality of successive image blocks each having a predetermined size of pixels;
• detector means for detecting a plurality of edge values each representative of peripheral pixels of a plurality of addresses of a corresponding one of said luminance signal, said first and second color-difference signals and said image block;
• scaling factor means for providing a selected scaling factor in dependence upon a first edge value representative of said peripheral pixels of said plurality of addresses of said luminance signal;
• block bit allocation means for allocating a number of bits of each image block in dependence upon said plurality of edge values to provide a number of allocation bits;
• means for determining a quantized width of said image signal in dependence upon said selected scaling factor to provide a quantized width signal;
• means for quantizing said image signal in dependence upon said quantized width signal to provide a quantized sampled signal;
• first encoder means for encoding said quantized sampled signal to provide a first encoded signal having a number of discrete DC factor bits;
• factor bit allocation means for subtracting said discrete DC factor bits from said allocation bits to provide AC allocation bits;
• second encoder means for encoding said quantized sampled signal to provide a second encoded signal having a number of discrete DC factor bits in dependence upon said AC allocation bits;
• and
• means for multiplexing between said first and second encoded signals to provide a compresses image signal.

A data compression device, comprising:

• means for receiving an image signal representative of a luminance signal and first and second color-difference signals, and for formatting said image signal into a plurality of successive image blocks each having a predetermined size of pixels;
• detector means for detecting a plurality of edge values each representative of peripheral pixels of a plurality of addresses of a corresponding ones of said luminance signal, said first and second color-difference signals and said image block;
• scaling factor means for providing a selected scaling factor in dependence upon a first edge value representative of said peripheral pixels of said plurality of addresses of said luminance signal;
• block bit allocation means for allocating a number of bits of each image block in dependence upon said plurality of edge values to provide a number of allocation bits;
• means for quantizing said image signal in dependence upon said selected scaling factor to provide a quantized sampled signal;
• factor bit allocation means for subtracting a number of discrete DC factor bits of said quantized sampled signal from said allocation bits to provide AC allocation bits;
• and
• means for encoding said quantized sampled signal to provide an encoded signal having a number of discrete DC factor bits in dependence upon said AC allocation bits.

A method for compressing digital image data, comprising the steps:

• formatting an image signal representative of a luminance signal and first and second color-difference signals into a plurality of successive image blocks each having a predetermined number of pixels;
• detecting a plurality of edge values each representative of peripheral pixels of a plurality of addresses of corresponding one of said luminance signal, said first and second color-difference signals and said image block;
• generating a selected scaling factor in dependence upon a first edge value representative of said peripheral pixels of said plurality of addresses of said luminance signal;
• generating a number of allocation bits by allocating a number of bits of each image block in dependence upon said plurality of edge values;
• generating a quantized sampled signal by quantizing said image signal in dependence upon said selected scaling factor;
• generating AC allocation bits by subtracting a number of discrete DC factor bits of said quantized sampled signal from said allocation bits;
• and
• generating an encoded signal having a number of discrete DC factor bits by encoding said quantized sampled signal in dependence upon said AC allocation bits.