fc7815d692
To be enabled with the flag WEBP_USE_THREAD. For now it's only available on unix (pthread), when using Makefile.unix Will be switched on more generally later. In-loop filtering and output (=rescaling/yuv->rgb conversion) is done in parallel to bitstream decoding, lagging 1 row behind. Example: examples/dwebp bryce.webp -v Time to decode picture: 0.680s examples/dwebp bryce.webp -v -mt Time to decode picture: 0.515s Change-Id: Ic30a897423137a3bdace9c4e30465ef758fe53f2
85 lines
2.5 KiB
Groff
85 lines
2.5 KiB
Groff
.\" Hey, EMACS: -*- nroff -*-
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.TH DWEBP 1 "June 20, 2011"
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.SH NAME
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dwebp \- decompress a WebP file to an image file
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.SH SYNOPSIS
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.B dwebp
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.RI [ options ] " input_file.webp
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.br
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.SH DESCRIPTION
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This manual page documents the
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.B dwebp
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command.
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.PP
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\fBdwebp\fP decompresses WebP files into PNG, PPM or PGM images.
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.SH OPTIONS
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The basic options are:
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.TP
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.B \-h
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Print usage summary.
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.TP
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.B \-version
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Print the version number (as major.minor.revision) and exit.
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.TP
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.B \-o string
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Specify the name of the output file (as PNG format by default).
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.TP
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.B \-ppm
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Change the output format to PPM.
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.TP
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.B \-pgm
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Change the output format to PGM. The output consist of luma/chroma
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samples instead of RGB, using the ICM4 layout. This option is mainly
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for verification and debugging purpose.
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.TP
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.B \-nofancy
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Don't use the fancy upscaler for YUV420. This may lead to jaggy
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edges (especially the red ones), but should be faster.
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.TP
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.B \-nofilter
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Don't use the in-loop filtering process even if it is required by
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the bitstream. This may produce visible blocks on the non-compliant output,
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but will make the decoding faster.
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.TP
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.B \-mt
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Use multi-threading for decoding, if possible.
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.TP
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.B \-crop x_position y_position width height
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Crop the decoded picture to a rectangle with top-left corner at coordinates
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(\fBx_position\fP, \fBy_position\fP) and size \fBwidth\fP x \fBheight\fP.
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This cropping area must be fully contained within the source rectangle.
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The top-left corner will be snapped to even coordinates if needed.
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This option is meant to reduce the memory needed for cropping large images.
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Note: the cropping is applied \fIbefore\fP any scaling.
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.TP
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.B \-scale width height
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Rescale the decoded picture to dimension \fBwidth\fP x \fBheight\fP. This option is
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mostly intended to reducing the memory needed to decode large images,
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when only a small version is needed (thumbnail, preview, etc.).
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Note: scaling is applied \fIafter\fP cropping.
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.TP
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.B \-v
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Print extra information (decoding time in particular).
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.TP
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.B \-noasm
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Disable all assembly optimizations.
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.SH Examples:
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dwebp picture.webp -o output.png
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.br
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dwebp picture.webp -ppm -o output.ppm
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.SH
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.SH SEE ALSO
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.BR cwebp (1).
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.br
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Please refer to http://code.google.com/speed/webp/ for additional
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information.
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.SH AUTHOR
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\fBdwebp\fP was written by the WebP team.
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.br
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The latest source tree is available at http://www.webmproject.org/code
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.PP
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This manual page was written by Pascal Massimino <pascal.massimino@gmail.com>,
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for the Debian project (and may be used by others).
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