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README: minor wording update
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README
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README
@ -9,7 +9,7 @@
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Description:
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============
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WEBP codec: Library to encode and decode images in WebP format. This package
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WebP codec: library to encode and decode images in WebP format. This package
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contains the library that can be used in other programs to add WebP support,
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as well as the command line tools 'cwebp' and 'dwebp'.
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@ -35,6 +35,8 @@ By running:
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the directory output\release-static\(x64|x86)\bin will contain the tools
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cwebp.exe and dwebp.exe. The directory output\release-static\(x64|x86)\lib will
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contain the libwebp static library.
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The target architecture (x86/x64) is detected by Makefile.vc from the Visual
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Studio compiler (cl.exe) available in the system path.
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Unix build using makefile.unix:
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-------------------------------
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@ -56,9 +58,6 @@ Using autoconf tools:
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make
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make install
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Note: In case './configure' step fails, try generating configure & appropriate
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Makefile(s) via command 'aclocal && autoconf && automake -a -c;'.
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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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@ -73,7 +72,7 @@ installed.
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Note: The encoding and decoding libraries are compiled separately
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(as src/dec/libwebpdecode.* and src/dec/libwebpencode.*). They
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can be installed independently using a minor modifications in the
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can be installed independently using a minor modification in the
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corresponding Makefile.am configure files (see comments there).
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SWIG bindings:
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@ -112,7 +111,7 @@ 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 one using a
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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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@ -196,7 +195,7 @@ Namely:
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Decoding tool:
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==============
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There is a decoding sample code as examples/dwebp.c which will take
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There is a decoding sample in examples/dwebp.c which will take
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a .webp file and decode it to a PNG image file (amongst other formats).
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This is simply to demonstrate the use of the API. You can verify the
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file test.webp decodes to exactly the same as test_ref.ppm by using:
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@ -227,7 +226,7 @@ Use following options to convert into alternate image formats:
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-noasm ....... disable all assembly optimizations.
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Encoding API:
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===========
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=============
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The main encoding functions are available in the header src/webp/encode.h
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The ready-to-use ones are:
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@ -243,10 +242,12 @@ size_t WebPEncodeBGRA(const uint8_t* bgra, int width, int height, int stride,
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They will convert raw RGB samples to a WebP data. The only control supplied
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is the quality factor.
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Advanced encoding API:
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----------------------
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A more advanced API is based on the WebPConfig and WebPPicture structures.
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WebPConfig contains the encoding settings and is not tied a to a particular
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WebPConfig contains the encoding settings and is not tied to a particular
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picture.
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WebPPicture contains input data, on which some WebPConfig will be used for
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compression.
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@ -278,14 +279,13 @@ The encoding flow looks like:
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if (!WebPPictureAllocate(&pic)) {
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return 0; // memory error
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}
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// add that point, 'pic' has been initialized as a container,
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// at this point, 'pic' has been initialized as a container,
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// and can receive the Y/U/V samples.
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// Alternatively, one could use ready-made import functions like
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// WebPPictureImportRGB(), which will take care of memory allocation.
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// In any case, past this point, one will have to call
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// WebPPictureFree(&pic) to reclaim memory.
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// Set up a byte-output write method. WebPMemoryWriter, for instance.
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WebPMemoryWriter wrt;
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pic.writer = MyFileWriter;
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@ -300,7 +300,6 @@ The encoding flow looks like:
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-------------------------------------- END PSEUDO EXAMPLE
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Decoding API:
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=============
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@ -322,7 +321,6 @@ 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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@ -354,7 +352,7 @@ 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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The idec object must always be released (even upon an error condition)
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by calling: WebPDelete(idec)
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by 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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@ -366,16 +364,14 @@ WebPINewRGB() or WebPINewYUV().
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Please have a look at the src/webp/decode.h header for further details.
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Advanced Decoding API:
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=========================
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======================
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WebP decoding supports Advanced API to provide ability to have on-the-fly
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cropping and rescaling, something of great usefulness on memory-constraint
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environments like mobile phones. Basically, the memory usage will scale with
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the output's size, not the input's when one only need a quick preview or a
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zoomed in portion of an otherwise too-large picture. Some CPU can be saved
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too, incidentally.
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WebP decoding supports an advanced API which provides on-the-fly cropping and
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rescaling, something of great usefulness on memory-constrained environments like
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mobile phones. Basically, the memory usage will scale with the output's size,
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not the input's, when one only needs a quick preview or a zoomed in portion of
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an otherwise too-large picture. Some CPU can be saved too, incidentally.
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-------------------------------------- BEGIN PSEUDO EXAMPLE
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// A) Init a configuration object
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@ -434,7 +430,6 @@ too, incidentally.
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-------------------------------------- END PSEUDO EXAMPLE
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Bugs:
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=====
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