METHOD AND APPARATUS FOR COMPRESSING AND DECOMPRESSING IMAGE DATA

A first comparator compares pixel data outputted by a pixel-data generating unit with an immediately preceding item of pixel data that has been latched by a first latch. The result of comparison is delivered to a first memory unit. If the result of comparison is that the two compared items of pixel data do not agree, a second comparator compares the pixel data outputted by the pixel-data generating unit with pixel data latched by a second latch. The result of this comparison is delivered to a second memory unit. If the result of the comparison performed by the second comparator is that the two compared items of pixel data do not agree, the pixel data from the generating unit is stored in a third memory unit. When the pixel data latched by the first latch does not agree with this pixel data, the content latched by the second latch is updated to the content latched by the first latch and the content latched by the first latch is updated to this pixel data.