Image compression device allowing rapid and highly precise encoding while suppressing code amount of image data after compression

An image compression device for compressing image data comprising:

• an encoder compressing and encoding input image data;
• and
• a control circuit causing said encoder to process sample image data to determine an optimal version of a compression parameter for rendering a code amount of image data after the compression of an image of one screen to be compressed equal to or smaller than a predetermined value;
• wherein said control circuit divides said image of one screen to be compressed into a plurality of blocks, extracts a predetermined block from said plurality of blocks with a regularity so as to extract the block uniformly across the one screen, and generates said sample image data.

An image compression device for compressing image data comprising:

• a discret cosine transformation circuit performing a two-dimensional discrete cosine transformation on image data constituting an image of one screen to generate a discrete cosine transformation coefficient;
• a quantization circuit quantizing the discrete cosine transformation coefficient supplied from said discrete cosine transformation circuit referring to a quantization threshold value stored in a preset quantization table;
• a Huffman encoding circuit performing a variable length encoding on the discrete cosine transformation coefficient quantized in said quantization circuit, referring to a Huffman code stored in a preset Huffman table to generate compression image data;
• a code amount counter counting a code amount of the compression image data generated by said Huffman encoding circuit;
• and
• a Huffman decoding circuit performing a variable length encoding on the compression image data generated by said Huffman encoding circuit referring to a Huffman code stored in a preset Huffman table, to generate decompression image data;
• an inverse quantization circuit performing an inverse quantization on the decompression image data generated by said Huffman decoding circuit referring to a quantization threshold value stored in a preset quantization table to generated a discrete cosine transformation coefficient and sending the generated discrete cosine transformation coefficient back to said quantization circuit;
• said quantization circuit quantizing the discrete cosine transformation coefficient sent back from said inverse quantization circuit referring to the quantization threshold value stored in the preset quantization table;
• and
• a control circuit repeatedly performing a compression process by said quantization circuit and said Huffman encoding circuit, said Huffman decoding circuit and said inverse quantization circuit, while changing a setting of a parameter constituted of said quantization threshold value and said Huffman code until the code amount of the compression image data counted by said code amount counter becomes equal to or smaller than a predetermined value, to determine an optimal version of said parameter for rendering the code amount of the compression image data equal to or smaller than the predetermined value.

An image data compression device for compressing image data comprising:

• a discreet cosine transformation circuit performing a two-dimensional discrete cosine transformation on image data constituting an image of one screen to generate a discrete cosine transformation coefficient;
• a quantization circuit quantizing the discrete cosine transformation coefficient supplied from said discrete cosine transformation circuit referring to a quantization threshold value stored in a preset quantization table;
• a Huffman encoding circuit performing a variable length encoding on the discrete cosine transformation coefficient quantized in said quantization circuit, referring to a Huffman code stored in a preset Huffman table to generate compression image data;
• a code amount counter counting a code amount of the compression image data generated by said Huffman encoding circuit;
• a Huffman decoding circuit performing a variable length decoding on the compression image data generated by said Huffman encoding circuit, referring to a Huffman code stored in a preset Huffman table, to generate decompression image data and sending said decompression image data back to said Huffman encoding circuit;
• said Huffman encoding circuit performing the variable length encoding on the decompression image data sent back from said Huffman decoding circuit referring to the Huffman code stored in the preset Huffman table;
• and
• a control circuit repeating a process by said Huffman encoding circuit and said Huffman decoding circuit while changing a setting of said Huffman code until the code amount of the compression image data counted by said code amount counter becomes equal to or smaller than a predetermined value, to determine an optimal version of said Huffman code for rendering the code amount of the compression image data equal to or smaller than the predetermined value.