forked from mirror/libbpg
libbpg-0.9.6
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103
README
103
README
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@ -8,12 +8,6 @@ BPG Image library and utilities
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options should be OK for Linux). Type 'make' to compile and 'make
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install' to install the compiled binaries.
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- x265 usage: for much increased compression speed (but lower
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quality), you can compile and install x265 and then enable its use
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in the Makefile. x265 supports by default only 8 bits per component
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and does not support monochrome encoding yet (hence no alpha nor
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grayscale images can be encoded with it).
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- bpgview: in order to compile it you need to install the SDL and
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SDL_image libraries.
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@ -27,24 +21,57 @@ BPG Image library and utilities
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- The BPG file format is specified in doc/bpg_spec.txt.
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2) BPG encoder
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2) Compilation and Installation Notes
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-------------------------------------
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2.1) Linux
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----------
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- Edit the Makefile to change the compile options (the default
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compile options should be OK). Type 'make' to compile and 'make
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install' to install the compiled binaries.
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- Use 'make -j N' where N is the number of CPU cores to compile faster.
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- The following packages must be installed: SDL-devel
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SDL_image-devel yasm. It is recommended to use yasm version >= 1.3.0
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to have a faster compilation.
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- Only a 64 bit target is supported because x265 needs it for bit
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depths > 8.
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2.2) Windows
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------------
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- Only cross-compilation from Linux is supported.
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- The following packages need to be installed: mingw64-gcc
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mingw64-libpng mingw64-libjpeg-turbo mingw64-SDL mingw64-SDL_image
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yasm. It is recommended to use yasm version >= 1.3.0 to have a
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faster compilation.
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- Only a 64 bit target is supported because x265 needs it for bit
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depths > 8.
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3) BPG encoder
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--------------
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The BPG command line encoder is 'bpgenc'. It takes JPEG or PNG images
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as input.
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- Speed: by default bpgenc uses the JCTVC encoder which has a high
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quality but is slow. If you compiled with x265, you can have a much
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faster encoding with the '-e x265' option. With x265 you can also
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select the encoding speed with the '-m' option (1 = fast, but larger
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image, 9 = slower but smaller image). Warning: x265 does not support
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monochrome (and alpha) yet, so you must use the JCTVC encoder for
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these cases.
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- Speed: by default bpgenc uses the x265. You can compile the much
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slower but more efficient JCTVC encoder and select it with the '-e
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jctvc' option. With x265 you can select the encoding speed with the
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'-m' option (1 = fast, but larger image, 9 = slower but smaller
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image).
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- Bit depth: the default bit depth is 8. You can increase it to 10
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('-b 10' option) to slightly increase the compression ratio. For web
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publishing it is generally not a good idea because the Javascript
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decoder uses more memory.
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decoder uses more memory. The compiled x265 encoder supports the bit
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depth of 8, 10 and 12. The slower JCTVC encoder can be compiled to
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support higher bit depths (up to 14) by enabling the Makefile
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define: USE_JCTVC_HIGH_BIT_DEPTH.
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- Lossless compression is supported as a bonus thru the HEVC lossless
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capabilities. Use a PNG input in this case unless you know what you
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@ -60,15 +87,8 @@ as input.
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- the JCTVC encoder gives smaller images than the x265 encoder
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with lossless compression.
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- There is a difference of interpretation of the quantizer parameter
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(-q option) between the x265 and JCTVC encoder. The default value is
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optimized for the JCTVC encoder, not for x265. We will try to align
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the x265 value to JCTVC in the future.
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- By default, the JCTVC encoder is limited to a precision of 12
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bits. You can enable high bit depths (up to 14) by enabling the
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Makefile define: USE_JCTVC_HIGH_BIT_DEPTH. The encoder is sligthly
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slower in this case.
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- There is a small difference of interpretation of the quantizer
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parameter (-q option) between the x265 and JCTVC encoder.
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- Color space and chroma format:
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@ -125,11 +145,11 @@ as input.
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with the '-keepmetadata' option. For JPEG input, EXIF, ICCP and XMP
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are copied. For PNG input, ICCP is copied.
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- Objective comparisons: the JCTVC encoder is tuned for PSNR only, not
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for SSIM, so you should use PSNR when making objective comparison
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with other formats. x265 is tuned by default for SSIM.
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- Objective comparisons: x265 is tuned by default for SSIM. the JCTVC
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encoder is tuned for PSNR only, not for SSIM, so you should use PSNR
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when making objective comparison with other formats.
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3) BPG decoder
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4) BPG decoder
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--------------
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The BPG command line decoder is bpgdec. It outputs a PNG or PPM
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@ -141,7 +161,7 @@ no decoded image is output).
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- The '-b' option selects the bit depth (8 or 16) of the PNG
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output. It is independent of the internal BPG bit depth.
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4) BPG viewer
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5) BPG viewer
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-------------
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The BPG image viewer uses the SDL library to display BPG images and
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@ -149,7 +169,7 @@ other image formats supported by the SDL_image library. The available
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keys are displayed by launching bpgview without parameters. bpgview
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supports BPG animations.
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5) BPG decoding library
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6) BPG decoding library
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-----------------------
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BPG images can be decoded in any program with the libbpg
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@ -161,7 +181,7 @@ provided as a static one.
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Currently there is no similar library for encoding so you should
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invoke the bpgenc utility.
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6) Javascript decoder
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7) Javascript decoder
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---------------------
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The following Javascript decoders are available, sorted by increasing size:
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@ -193,7 +213,7 @@ be avoided, as with animated GIFs.
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asm.js gives an interesting speed boost, so we hope that more browsers
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will support this Javascript subset.
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7) FFmpeg modifications
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8) FFmpeg modifications
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-----------------------
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- Completed support of chroma_format_idc = 0 (monochrome mode).
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@ -217,16 +237,25 @@ will support this Javascript subset.
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- Stripped FFmpeg from all codecs except HEVC and the necessary
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support code.
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8) Licensing
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------------
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9) x265 modifications
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---------------------
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- Support of monochrome format (some part not used by BPG may be
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missing).
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- Support of static build.
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10) Licensing
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-------------
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- libbpg and bpgdec are released under the LGPL license (the FFmpeg
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part is under the LGPL, the BPG specific part is released under the
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BSD license).
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- bpgenc is released under the BSD license (it includes the JCTVC code
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which is released under the BSD license. The BPG specific part is
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released under the BSD license).
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- bpgenc is released under the GPL version 2 license. The BPG specific
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code is released under the BSD license. The JCTVC code is released
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under the BSD license. The x265 code is released under the GPL
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version 2 license.
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- BPG relies on the HEVC compression technology which may be protected
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by patents in some countries. Most devices already include or will
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