Partial image decompression of a tiled image
View Patent ↗A decompression unit is configured to partially decompress a compressed image formed by compressed tiles. Each compressed tiles correspond to a tile of the uncompressed image. The decompression unit selects a subset of relevant tiles, which are visible in a view window or a view frustum. Specifically, the decompression unit includes a tile selector to select the relevant tile and a tile decompressor to decompress the relevant tiles. By decompressing only a subset of the compressed tiles, the decompression unit reduces the processing time required to generate the contents of the view window.
1. A method for partially decompressing a compressed image having a plurality of compressed tiles, wherein each compressed tile corresponds to a tile, wherein each tile has a plurality of vertices, the method comprising:
classifying each vertex of each tile by;
determining whether each vertex is above a view frustum;
determining whether each vertex is below the view frustum;
determining whether each vertex is the right of the view frustum; and
determining whether each vertex is to the left of the view frustum;
setting a first bit of a bit code of a vertex when the vertex is to the left of the view frustum;
setting a second bit of the bit code of the vertex when the vertex is to the right of the view frustum;
setting a third bit of the bit code of the vertex when the vertex is below the view frustum; and
setting a fourth bit of the bit code of a vertex when the vertex is above the view frustum;
selecting a plurality of relevant tiles by:
selecting each tile as a relevant tile when a bitwise logic AND of a bit-code of a first vertex of a tile with a bit-code of a second vertex of the tile is equal to zero, wherein said first vertex and said vertex are adjacent vertices; and
selecting each tile as a relevant tile when a bitwise XOR of the bit-code the first vertex with a bit-code of a first opposite vertex is equal to 1111 b and a bitwise XOR of the bit-code of the second vertex with a bit-code of a second opposite vertex is equal to 1111 b;
retrieving a compressed tile corresponding to each relevant tile thereby forming a plurality of relevant compressed tiles; and
decompressing each of the relevant compressed tile.
2. The method of claim 1 , wherein selecting a plurality of relevant tiles comprises:
selecting each tile that encompasses the view frustum;
selecting each tile contained within the view frustum; and
selecting each tile having at least one side crossing a side of the view frustum.
3. The method of claim 1 , wherein selecting a plurality of relevant tiles comprises:
selecting each tile that encompasses a view window;
selecting each tile contained within the view window; and
selecting each tile having at least one side crossing a side of the view window.
4. The method of claim 1 , wherein classifying each vertex of each tile further comprises:
determining whether each vertex is above a view window;
determining whether each vertex is below the view window;
determining whether each vertex is to the right of the view window; and
determining whether each vertex is to the left of the view window.
5. A decompression unit for decompressing a compressed image having a plurality of compressed tiles wherein each compressed tile corresponds to a tile and each tile has a plurality of vertices, the decompression unit comprising:
a tile vertex classifier coupled to the tile selector and configured to assign a bit code to the vertices of each tile, wherein the tile vertex classifier is configured to:
set a first bit of a bit code of a vertex when the vertex is to the left of a view window;
set a second bit of the bit code of the vertex when the vertex is to the right of the view window;
set a third bit of the bit code of the view window;
set a third bit of the bit code of the vertex when the vertex is below the view window; and
set a fourth bit of the bit code of a vortex when the vertex is above the view window;
a tile selector configured to receive the compressed image and to select a plurality of relevant tiles, by:
selecting each tile as a relevant tile when a bitwise logic AND of a bit-code of a first vertex of a tile with a bit-code of a second vertex of the tile is equal to zero, wherein said first vertex and said second vertex are adjacent vertices; and
selecting each tile as a relevant tile when a bitwise XOR of the bit-code the first vertex with a bit-code of a first opposite vertex is equal to 1111 b and a bitwise XOR of the bit-code of the second vertex with a bit-code of a second opposite vertex is equal to 1111 b ; and
a tile decompressor coupled to the tile selector and configured to decompress each compressed tile corresponding to one of the relevant tiles.
6. The decompression unit of claim 5 , wherein said tile selector uses the view window to select the plurality of relevant tiles.
7. The decompression unit of claim 6 , wherein the tile selector is configured to select a tile as relevant when the tile is visible in the view window.
8. The decompression unit of claim 6 , wherein the tile selector is configured to select a tile as relevant when the tile is visible in a view frustum of the view window.
9. The decompression unit of claim 5 , wherein the tile vertex classifier is configured to determine if a vertex is above, below, to the left of, to the right of, or within a view window.
10. The decompression unit of claim 5 , wherein the tile vertex classifier is configured to determine if a vertex is above, below, to the left of, to the right of, or within a view frustum of the view window.