Sample Level Variation For Spatial Sub-sampled Images

A computer-readable storage medium storing instrictions which when executed by a data processing system cause the data processing system to perform operations that process data, the operations comprising:

• determining an initial sample level value for the sample;
• computing an area of influence of the sample, the area of influence including pixels for which the sample is a factor in a prediction thereof;
• computing prediction errors of pixels in the area of influence;
• computing a prediction error of the sample from the prediction errors of the pixels;
• computing, if the prediction error of the sample exceeds a prediction error threshold, a sample level change for the sample based only on the prediction errors of the pixels;
• and
• assigning, if the sample level change is less than a level change threshold, a new sample level value to the sample based on the sample level change.

A system comprising:

• a processor coupled to a bus;
• a memory coupled to the processor through the bus;
• instructions executed by the processor from the memory to cause the processor
• to determine an initial sample level value for the sample,
• compute an area of influence of the sample, the area of influence including pixels for which the sample is a factor in a prediction thereof,
• compute prediction errors of pixels in the area of influence;
• compute a prediction error of the sample from the prediction errors of the pixels,
• compute, if the prediction error of the sample exceeds a prediction error threshold, a sample level change for the sample based only on the prediction errors of the pixels,
• and assign, if the sample level change is less than a level change threshold, a new sample level value to the sample based on the sample level change.

An apparatus comprising:

• means for receiving image data comprising pixels and an irregular spatial sample;
• means for determining an initial sample level value for the sample;
• means for computing an area of influence of the sample, the area of influence including pixels for which the sample is a factor in a prediction thereof;
• means for computing prediction errors of pixels in the area of influence;
• means for computing a prediction error of the sample from the prediction errors of the pixels;
• means for computing, if the prediction error of the sample exceeds a prediction error threshold, a sample level change for the sample based only on the prediction errors of the pixels;
• means for assigning, if the sample level change is less than a level change threshold, a new sample level value to the sample based on the sample level change;
• and
• means for outputting the sample.