  Inpainting-based image compression is emerging as a promising competitor to
transform-based compression techniques. Its key idea is to reconstruct image
information from only few known regions through inpainting. Specific partial
differential equations (PDEs) such as edge-enhancing diffusion (EED) give high
quality reconstructions of image structures with low or medium texture. Even
though the strengths of PDE- and transform-based compression are complementary,
they have rarely been combined within a hybrid codec. We propose to sparsify
blocks of a JPEG compressed image and reconstruct them with EED inpainting. Our
codec consistently outperforms JPEG and gives useful indications for
successfully developing hybrid codecs further. Furthermore, our method is the
first to choose regions rather than pixels as known data for PDE-based
compression. It also gives novel insights into the importance of corner regions
for EED-based codecs.
