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Replace high ASCII artifacts (curly quotes, etc.).

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modified:   doc/webp-lossless-bitstream-spec.txt
Change-Id: I9dd9d4ed05c8f93d4cafadf8c99cc21c300a9299
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Lou Quillio 2012-05-31 13:04:19 -07:00
parent 930e8abbda
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doc/webp-lossless-bitstream-spec.txt
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@ -27,7 +27,7 @@ used entropy codes, spatial predictors, color space conversion, and
color table. LZ77, Huffman coding, and a color cache are used for color table. LZ77, Huffman coding, and a color cache are used for
compression of the bulk data. Decoding speeds faster than PNG have compression of the bulk data. Decoding speeds faster than PNG have
been demonstrated, as well as 25 % denser compression than what can be been demonstrated, as well as 25 % denser compression than what can be
achieved using today’s PNG format. achieved using today's PNG format.
* TOC placeholder * TOC placeholder
@ -141,13 +141,13 @@ RIFF Header
The beginning of the header has the RIFF container. This consist of the The beginning of the header has the RIFF container. This consist of the
following 21 bytes: following 21 bytes:
1. String “RIFF” 1. String "RIFF"
2. A little-endian 32 bit value of the block length, the whole size of 2. A little-endian 32 bit value of the block length, the whole size of
the block controlled by the RIFF header. Normally this equals the the block controlled by the RIFF header. Normally this equals the
payload size (file size subtracted by 8 bytes, i.e., 4 bytes for payload size (file size subtracted by 8 bytes, i.e., 4 bytes for
‘RIFF’ identifier and 4 bytes for storing this value itself). 'RIFF' identifier and 4 bytes for storing this value itself).
3. String “WEBP” (RIFF container name). 3. String "WEBP" (RIFF container name).
4. String “VP8L” (chunk tag for lossless encoded image data). 4. String "VP8L" (chunk tag for lossless encoded image data).
5. A little-endian 32-bit value of the number of bytes in the lossless 5. A little-endian 32-bit value of the number of bytes in the lossless
stream. stream.
6. One byte signature 0x64. Decoders need to accept also 0x65 as a valid 6. One byte signature 0x64. Decoders need to accept also 0x65 as a valid
@ -175,7 +175,7 @@ correlations. Transformations can make the final compression more dense.
An image can go through four types of transformations. A 1 bit indicates An image can go through four types of transformations. A 1 bit indicates
the presence of a transform. Every transform is allowed to be used only the presence of a transform. Every transform is allowed to be used only
once. The transformations are used only for the main level ARGB image — the once. The transformations are used only for the main level ARGB image -- the
subresolution images have no transforms, not even the 0 bit indicating the subresolution images have no transforms, not even the 0 bit indicating the
end-of-transforms. end-of-transforms.
@ -611,7 +611,7 @@ code, and in order to minimize this cost, statistically similar blocks can
share an entropy code. The blocks sharing an entropy code can be found by share an entropy code. The blocks sharing an entropy code can be found by
clustering their statistical properties, or by repeatedly joining two clustering their statistical properties, or by repeatedly joining two
randomly selected clusters when it reduces the overall amount of bits randomly selected clusters when it reduces the overall amount of bits
needed to encode the image. [See section “Decoding of meta Huffman codes” needed to encode the image. [See section "Decoding of meta Huffman codes"
in Chapter 5 for an explanation of how this entropy image is stored.] in Chapter 5 for an explanation of how this entropy image is stored.]
Each pixel is encoded using one of three possible methods: Each pixel is encoded using one of three possible methods:
@ -685,7 +685,7 @@ length to 4096. For distances, all 40 prefix codes are used.
within the current pixel. The rest are pure distance codes in scan-line within the current pixel. The rest are pure distance codes in scan-line
order, just offset by 120. The smallest codes are coded into x and y order, just offset by 120. The smallest codes are coded into x and y
offsets by the following table. Each tuple shows the x and the y offsets by the following table. Each tuple shows the x and the y
coordinates in 2d offsets — for example the first tuple (0, 1) means 0 for coordinates in 2d offsets -- for example the first tuple (0, 1) means 0 for
no difference in x, and 1 pixel difference in y (indicating previous row). no difference in x, and 1 pixel difference in y (indicating previous row).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -768,7 +768,7 @@ result of this coding is further Huffman coded.
### Spatially-variant Huffman coding ### Spatially-variant Huffman coding
For every pixel (x, y) in the image, there is a definition of which entropy For every pixel (x, y) in the image, there is a definition of which entropy
code to use. First, there is an integer called ‘meta Huffman code’ that can code to use. First, there is an integer called 'meta Huffman code' that can
be obtained from a subresolution 2d image. This meta Huffman code be obtained from a subresolution 2d image. This meta Huffman code
identifies a set of five Huffman codes, one for green (along with length identifies a set of five Huffman codes, one for green (along with length
codes and color cache codes), one for each of red, blue and alpha, and one codes and color cache codes), one for each of red, blue and alpha, and one
@ -964,9 +964,9 @@ the number of pixels (xsize * ysize).
(1-bit value 1; 4-bit value for color cache size) (1-bit value 1; 4-bit value for color cache size)
<huffman codes> ::= <huffman code> | <huffman code><huffman codes> <huffman codes> ::= <huffman code> | <huffman code><huffman codes>
<huffman code> ::= <simple huffman code> | <normal huffman code> <huffman code> ::= <simple huffman code> | <normal huffman code>
<simple huffman code> ::= see “Simple code length code” for details <simple huffman code> ::= see "Simple code length code" for details
<normal huffman code> ::= <code length code>; encoded code lengths <normal huffman code> ::= <code length code>; encoded code lengths
<code length code> ::= see section “Normal code length code” <code length code> ::= see section "Normal code length code"
<lz77-coded image> ::= (<argb-pixel> | <color-cache-code> | <lz77-copy>) | <lz77-coded image> ::= (<argb-pixel> | <color-cache-code> | <lz77-copy>) |
(<lz77-coded image> | "") (<lz77-coded image> | "")
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~