From c37c23e5943ef5cd59dba70b2a996ebfdbe384c7 Mon Sep 17 00:00:00 2001 From: James Zern Date: Thu, 19 Jul 2012 11:40:42 -0700 Subject: [PATCH] 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 --- README | 57 +++++++++++++++++++++++++++++++++------------------------ 1 file changed, 33 insertions(+), 24 deletions(-) diff --git a/README b/README index 395ed733..a30d0090 100644 --- a/README +++ b/README @@ -49,11 +49,13 @@ will build the binaries examples/cwebp and examples/dwebp, along with the static library src/libwebp.a. No system-wide installation is supplied, as this is a simple alternative to the full installation system based on the autoconf tools (see below). -Please refer the makefile.unix for additional details and customizations. +Please refer to the makefile.unix for additional details and customizations. Using autoconf tools: --------------------- -./autogen.sh +When building from git sources, you will need to run autogen.sh to generate the +configure script. + ./configure make make install @@ -61,7 +63,6 @@ make install should be all you need to have the following files /usr/local/include/webp/decode.h -/usr/local/include/webp/decode_vp8.h /usr/local/include/webp/encode.h /usr/local/include/webp/types.h /usr/local/lib/libwebp.* @@ -85,17 +86,22 @@ Currently the following functions are mapped: Decode: WebPGetDecoderVersion WebPGetInfo - WebPDecodeRGB WebPDecodeRGBA WebPDecodeARGB - WebPDecodeBGR WebPDecodeBGRA + WebPDecodeBGR + WebPDecodeRGB + Encode: WebPGetEncoderVersion - WebPEncodeRGB WebPEncodeRGBA - WebPEncodeBGR WebPEncodeBGRA + WebPEncodeRGB + WebPEncodeBGR + WebPEncodeLosslessRGBA + WebPEncodeLosslessBGRA + WebPEncodeLosslessRGB + WebPEncodeLosslessBGR Java bindings: @@ -111,9 +117,13 @@ decoding (dwebp) images. The easiest use should look like: cwebp input.png -q 80 -o output.webp -which will convert the input PNG or JPEG file to a WebP file using a -quality factor of 80 on a 0->100 scale (0 being the lowest quality, -100 being the best. Default value is 75). +which will convert the input file to a WebP file using a quality factor of 80 +on a 0->100 scale (0 being the lowest quality, 100 being the best. Default +value is 75). +You might want to try the -lossless flag too, which will compress the source +(in RGBA format) without any loss. The -q quality parameter will in this case +control the amount of processing time spent trying to make the output file as +small as possible. A longer list of options is available using the -longhelp command line flag: @@ -192,10 +202,11 @@ Namely: but with better quality. Typical value is around '75'. * 'f' option directly links to the filtering strength used by the codec's - in-loop processing. The higher, the smoother will highly-compressed area - look. This is particularly useful when aiming at very small files. - Typical values are around 20-30. Note that using the option -strong will - change the type of filtering. Use "-f 0" to turn filtering off. + in-loop processing. The higher the value, the smoother the + highly-compressed area will look. This is particularly useful when aiming + at very small files. Typical values are around 20-30. Note that using the + option -strong will change the type of filtering. Use "-f 0" to turn + filtering off. * 'm' controls the trade-off between encoding speed and quality. Default is 4. You can try -m 5 or -m 6 to explore more (time-consuming) encoding possibilities. A lower value will result in faster encoding at the expense @@ -342,20 +353,18 @@ This is mainly just one function to call: #include "webp/decode.h" uint8_t* WebPDecodeRGB(const uint8_t* data, size_t data_size, - int *width, int *height); + int* width, int* height); Please have a look at the file src/webp/decode.h for the details. There are variants for decoding in BGR/RGBA/ARGB/BGRA order, along with decoding to raw Y'CbCr samples. One can also decode the image directly into a pre-allocated buffer. -To detect a WebP file and gather picture's dimensions, the function: +To detect a WebP file and gather the picture's dimensions, the function: int WebPGetInfo(const uint8_t* data, size_t data_size, - int *width, int *height); + int* width, int* height); is supplied. No decoding is involved when using it. -A lower-level API is available from the header file - Incremental decoding API: ========================= @@ -383,15 +392,15 @@ or by just mentioning the new size of the transmitted data: WebPIUpdate(idec, buffer, size_of_transmitted_buffer); -Note that 'buffer' can be modified between each calls to WebPIUpdate, in +Note that 'buffer' can be modified between each call to WebPIUpdate, in particular when the buffer is resized to accommodate larger data. These functions will return the decoding status: either VP8_STATUS_SUSPENDED if -decoding is not finished yet, or VP8_STATUS_OK when decoding is done. -Any other status is an error condition. +decoding is not finished yet or VP8_STATUS_OK when decoding is done. Any other +status is an error condition. -The idec object must always be released (even upon an error condition) -by calling: WebPDelete(idec). +The 'idec' object must always be released (even upon an error condition) by +calling: WebPDelete(idec). To retrieve partially decoded picture samples, one must use the corresponding method: WebPIDecGetRGB or WebPIDecGetYUV.