08-17-2017, 12:45 AM
Structure and Texture Filling-In of Missing Image Blocks in Wireless Transmission and Compression Applications
INTRODUCTION
lossy JPEG compression is used for general purpose images. The JPEG algorithm divides the image into blocks of 8 by 8 pixels and calculates a two-dimensional discrete cosine transform (DCT), followed by quantization and
Huffman encoding. a single block or several consecutive blocks of an image maybe lost when transmitted over the wireless channel. even if a single block is lost,
the remaining blocks in that line might be received without their correct dc value because JPEG uses differential encoding for storing the dc value of successive pixels. forward error
correction (FEC) and automatic retransmission query protocols
(ARQ) are the main techniques used to make the transmisson more robust.
PROPOSED ALGORITHM
The following three computationally
efficient steps are followed for reconstruction of the lost block:
1)classify lost blocks into texture and structure
2)synthesize blocks which were classified as texture (use
texture synthesis);
3)fill in blocks which were classified as structure (use image
inpainting).
Block Classification:
This decision is taken at the receiver
by querying the region surrounding the lost block.we use
a simple coarseness measure given by the number of local extrema
in the neighborhood of the lost block To determine
whether or not a block has texture or noise.
Texture Synthesis:
when a block is classified as having texture, the entire 8-neighborhood of that block has texture. The missing block is then filled-in with the
texture from its surrounding.
Image Inpainting:
Structure in an image can be an edge between two regions or
a deterministic change in color or gray value.the digital inpainting procedure is applied when the block
classification algorithm detects a structured block.
For more details refer this pdf:
http://ivms.stanford.edu/ srane/papers/rane03ieetrip.pdf
ima.umn.edu/preprints/scanned-preprint/preprints5/1766.pdf