Morphological Anti-Ringing Filter for Lossy Image Compression

An apparatus for encoding blocks of an image, the blocks comprising a block of first values, the apparatus comprising:

• a memory;
• and
• a processor, wherein the processor is configured to execute instructions stored in the memory to:
• generate a transform block for the block of first values;
• generate quantized transform coefficients for the transform block;
• determine a clamping value for the block, the clamping value used to clamp second values, the second values corresponding to the first values and resulting from inverse transforming the transform block;
• encode the clamping value in a compressed bitstream;
• and
• encode the quantized transform coefficients in the compressed bitstream.

An apparatus for decoding a block of an image, comprising:

• a memory;
• and
• a processor, wherein the processor is configured to execute instructions stored in the memory to:
• decode, from a compressed bitstream, a quantized transform block;
• obtain, using the quantized transform block, a decoded block of pixel values;
• obtain a clamping value for the block;
• and
• clamp the pixel values using the clamping value.