JPEG packed block data structure for enhanced image processing
View Patent ↗An intermediate data format which is readily convertible to or from JPEG compliant data streams and to or from image data provides, in most circumstances, accelerated encoding and decoding in a degree sufficient to allow additional processing without necessitating increase of processor power even in relatively time-critical applications such as high-speed printers and image browsers. The format features flags which indicate if S>8 (indicating that extra bits are required to uniquely encode an orthogonal transform coefficient value) or runs of zero-valued orthogonal transform coefficients longer than sixteen are present in a block of data. The block of data can be tested for these conditions and flags set once per block or once per image. Extensive processing can thus be omitted if either or both of these conditions are not present, as will generally be the case.
1. A method of coding image data into at least one block of data including a plurality of coefficient values, said method including the steps of
testing said coefficient values for coefficient values requiring more than eight bits to be uniquely coded, and
using a flag in said at least one block of data to indicate if all said coefficient values in said block are coded in eight bits or fewer or if any coefficient value requires more than eight bits to be uniquely coded.
2. A method as recited in claim 1 wherein said coefficient values are DCT coefficients.
3. A method as recited in claim 2 wherein said DCT coefficients are AC DCT coefficients.
4. A method as recited in claim 1 , wherein said testing step is performed once per image.
5. A method as recited in claim 1 , wherein said testing step is performed once per block.
6. A method as recited in claim 1 including the further step of using another flag in a block of data to indicate if any ZRLs are present.