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README: cosmetics
- update swig function references - remove references to decode_vp8.h (no longer installed) - add lossless references - some grammar/spelling changes Change-Id: Icebfbcf6f638762f42d844b6bd3c0129c64d9340
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README
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README
@ -49,11 +49,13 @@ will build the binaries examples/cwebp and examples/dwebp, along
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with the static library src/libwebp.a. No system-wide installation
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is supplied, as this is a simple alternative to the full installation
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system based on the autoconf tools (see below).
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Please refer the makefile.unix for additional details and customizations.
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Please refer to the makefile.unix for additional details and customizations.
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Using autoconf tools:
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---------------------
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./autogen.sh
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When building from git sources, you will need to run autogen.sh to generate the
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configure script.
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./configure
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make
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make install
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@ -61,7 +63,6 @@ make install
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should be all you need to have the following files
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/usr/local/include/webp/decode.h
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/usr/local/include/webp/decode_vp8.h
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/usr/local/include/webp/encode.h
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/usr/local/include/webp/types.h
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/usr/local/lib/libwebp.*
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@ -85,17 +86,22 @@ Currently the following functions are mapped:
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Decode:
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WebPGetDecoderVersion
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WebPGetInfo
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WebPDecodeRGB
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WebPDecodeRGBA
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WebPDecodeARGB
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WebPDecodeBGR
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WebPDecodeBGRA
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WebPDecodeBGR
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WebPDecodeRGB
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Encode:
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WebPGetEncoderVersion
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WebPEncodeRGB
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WebPEncodeRGBA
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WebPEncodeBGR
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WebPEncodeBGRA
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WebPEncodeRGB
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WebPEncodeBGR
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WebPEncodeLosslessRGBA
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WebPEncodeLosslessBGRA
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WebPEncodeLosslessRGB
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WebPEncodeLosslessBGR
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Java bindings:
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@ -111,9 +117,13 @@ decoding (dwebp) images.
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The easiest use should look like:
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cwebp input.png -q 80 -o output.webp
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which will convert the input PNG or JPEG file to a WebP file using a
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quality factor of 80 on a 0->100 scale (0 being the lowest quality,
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100 being the best. Default value is 75).
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which will convert the input file to a WebP file using a quality factor of 80
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on a 0->100 scale (0 being the lowest quality, 100 being the best. Default
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value is 75).
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You might want to try the -lossless flag too, which will compress the source
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(in RGBA format) without any loss. The -q quality parameter will in this case
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control the amount of processing time spent trying to make the output file as
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small as possible.
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A longer list of options is available using the -longhelp command line flag:
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@ -192,10 +202,11 @@ Namely:
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but with better quality.
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Typical value is around '75'.
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* 'f' option directly links to the filtering strength used by the codec's
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in-loop processing. The higher, the smoother will highly-compressed area
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look. This is particularly useful when aiming at very small files.
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Typical values are around 20-30. Note that using the option -strong will
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change the type of filtering. Use "-f 0" to turn filtering off.
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in-loop processing. The higher the value, the smoother the
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highly-compressed area will look. This is particularly useful when aiming
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at very small files. Typical values are around 20-30. Note that using the
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option -strong will change the type of filtering. Use "-f 0" to turn
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filtering off.
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* 'm' controls the trade-off between encoding speed and quality. Default is 4.
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You can try -m 5 or -m 6 to explore more (time-consuming) encoding
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possibilities. A lower value will result in faster encoding at the expense
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@ -342,20 +353,18 @@ This is mainly just one function to call:
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#include "webp/decode.h"
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uint8_t* WebPDecodeRGB(const uint8_t* data, size_t data_size,
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int *width, int *height);
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int* width, int* height);
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Please have a look at the file src/webp/decode.h for the details.
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There are variants for decoding in BGR/RGBA/ARGB/BGRA order, along with
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decoding to raw Y'CbCr samples. One can also decode the image directly into a
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pre-allocated buffer.
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To detect a WebP file and gather picture's dimensions, the function:
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To detect a WebP file and gather the picture's dimensions, the function:
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int WebPGetInfo(const uint8_t* data, size_t data_size,
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int *width, int *height);
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int* width, int* height);
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is supplied. No decoding is involved when using it.
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A lower-level API is available from the header file <webp/decode_vp8.h>
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Incremental decoding API:
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=========================
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@ -383,15 +392,15 @@ or by just mentioning the new size of the transmitted data:
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WebPIUpdate(idec, buffer, size_of_transmitted_buffer);
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Note that 'buffer' can be modified between each calls to WebPIUpdate, in
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Note that 'buffer' can be modified between each call to WebPIUpdate, in
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particular when the buffer is resized to accommodate larger data.
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These functions will return the decoding status: either VP8_STATUS_SUSPENDED if
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decoding is not finished yet, or VP8_STATUS_OK when decoding is done.
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Any other status is an error condition.
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decoding is not finished yet or VP8_STATUS_OK when decoding is done. Any other
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status is an error condition.
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The idec object must always be released (even upon an error condition)
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by calling: WebPDelete(idec).
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The 'idec' object must always be released (even upon an error condition) by
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calling: WebPDelete(idec).
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To retrieve partially decoded picture samples, one must use the corresponding
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method: WebPIDecGetRGB or WebPIDecGetYUV.
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