Image block classification based on entropy of differences

Apparatus for detecting edges in an image block by determining entropies of pixel differences in the block.

The apparatus of claim 12, wherein the processor includes a look-up table of pre-computed bin entropies a function of bin height;

• and wherein the processor looks up entropies for bins of the histogram and sums the bin entropies to determine the entropy of the histogram.

The apparatus of claim 12, wherein the processor also determines a maximum pixel difference in the block.

The apparatus of claim 14, wherein the processor compares the entropy and maximum difference to thresholds to determine whether the block contains an edge.

The apparatus of claim 15, wherein the processor identifies a block having low entropy and a high maximum difference as a block containing at least one edge.

An article for a processor, the article comprising:

• computer memory;
• and
• a program stored in the memory, the program, when executed, causing the processor to determine whether an image block contains an edge by determining an entropy of pixel luminance differences in the block.

The article of claim 19, wherein the program also causes the processor to determine a maximum pixel difference in the block and use the maximum difference to determine whether the block contains at least one edge.