Picture data compression device and red data detection device

A red data detection device, comprising:

• upper bit extracting means for extracting only upper three bits of red-hued data supplied as 8-bit bi-level data and outputting the extracted upper three bits;
• threshold data outputting means for outputting, as threshold data, the upper three bits of 8-bit bi-level data that is near a reference value used in detecting red data and that may be divided out by a power of 2, where an exponent is an integer, said threshold data being than less and never equal to said reference value;
• comparator means for comparing the red-hued data with the threshold data, said comparator means selectively outputting high-level red detection data indicating that the picture data is the red data when the red data is larger than the threshold data or outputting the low-level red detection data indicating that the picture data is not red data when the red data is smaller than the threshold data;
• upper most bit extracting means for extracting an upper most bit of blue-hued data supplied as 8-bit bi-level data and outputting the extracted upper most bit;
• inverting means for complementing the upper most bit of low-level blue-hued data indicating that the picture data is the red data when said upper most bit is supplied from said upper most bit extracting means and outputting the inverted data as a high-level red detection data, and for complementing an upper most bit of high-level blue-hued data indicating that the picture data is not the red data when said upper most bit is supplied from said upper most bit extracting means and outputting the inverted data as a low-level red detection data;
• red data detection means for outputting high-level red detection data indicating that the picture data is red data when only high-level red detection data is supplied from said comparator means at the same time as high-level red detection data is supplied from said inverting means;
• and
• a red block decision data outputting means having its count value reset for each of pre-set units of picture data and having its count value set to a power of 2, where an exponent is a natural number, said red block decision data outputting means counting the high-level red detection data from the red data detection means for each of the pre-set units of the picture data and outputting red block decision data indicating that the pre-set unit of the picture data is red picture data when the count value of the red detection data reaches the pre-set count value.

A picture compression device, comprising:

• a blocking circuit for dividing picture data into a plurality of blocks, each block having a predetermined number of pixels, and for outputting the block-based picture data;
• a transform coding circuit for coding the block-based picture data on a block-by-block basis and for generating transform coefficients defining the picture data as a result of the coding;
• a red hue detector for determining whether a block received from said blocking circuit is a red-hued block, said red hue detector comprising (a) a red data extraction circuit for extracting a predetermined number of bits from 8-bit data representing the picture data, (b) a threshold data outputting circuit for supplying the same said predetermined number of bits derived from an 8-bit threshold value, and (c) a comparator for comparing said predetermined number of bits of said 8-bit data to said predetermined number of bits of said 8-bit threshold value to determine whether said block has more than a predetermined number of red-hued pixels in the picture data, said 8-bit threshold value being the closest to a reference value that is used in detecting red data and being less than and never equal to said reference value such that said 8-bit threshold value is divisible by 2″ where n is an integer;
• a quantization circuit for quantizing the transform coefficients;
• and
• a controller for controlling a quantization step of said quantization circuit if said block is detected as a red-hued block.