| .\" Hey, EMACS: -*- nroff -*- |
| .TH DWEBP 1 "June 23, 2016" |
| .SH NAME |
| dwebp \- decompress a WebP file to an image file |
| .SH SYNOPSIS |
| .B dwebp |
| .RI [ options ] " input_file.webp |
| .br |
| .SH DESCRIPTION |
| This manual page documents the |
| .B dwebp |
| command. |
| .PP |
| \fBdwebp\fP decompresses WebP files into PNG, PAM, PPM or PGM images. |
| .SH OPTIONS |
| The basic options are: |
| .TP |
| .B \-h |
| Print usage summary. |
| .TP |
| .B \-version |
| Print the version number (as major.minor.revision) and exit. |
| .TP |
| .BI \-o " string |
| Specify the name of the output file (as PNG format by default). |
| Using "-" as output name will direct output to 'stdout'. |
| .TP |
| .BI \-\- " string |
| Explicitly specify the input file. This option is useful if the input |
| file starts with an '\-' for instance. This option must appear \fBlast\fP. |
| Any other options afterward will be ignored. If the input file is "\-", |
| the data will be read from \fIstdin\fP instead of a file. |
| .TP |
| .B \-bmp |
| Change the output format to uncompressed BMP. |
| .TP |
| .B \-tiff |
| Change the output format to uncompressed TIFF. |
| .TP |
| .B \-pam |
| Change the output format to PAM (retains alpha). |
| .TP |
| .B \-ppm |
| Change the output format to PPM (discards alpha). |
| .TP |
| .B \-pgm |
| Change the output format to PGM. The output consists of luma/chroma |
| samples instead of RGB, using the IMC4 layout. This option is mainly |
| for verification and debugging purposes. |
| .TP |
| .B \-yuv |
| Change the output format to raw YUV. The output consists of |
| luma/chroma-U/chroma-V samples instead of RGB, saved sequentially as |
| individual planes. This option is mainly for verification and debugging |
| purposes. |
| .TP |
| .B \-nofancy |
| Don't use the fancy upscaler for YUV420. This may lead to jaggy |
| edges (especially the red ones), but should be faster. |
| .TP |
| .B \-nofilter |
| Don't use the in-loop filtering process even if it is required by |
| the bitstream. This may produce visible blocks on the non-compliant output, |
| but it will make the decoding faster. |
| .TP |
| .BI \-dither " strength |
| Specify a dithering \fBstrength\fP between 0 and 100. Dithering is a |
| post-processing effect applied to chroma components in lossy compression. |
| It helps by smoothing gradients and avoiding banding artifacts. |
| .TP |
| .BI \-alpha_dither |
| If the compressed file contains a transparency plane that was quantized |
| during compression, this flag will allow dithering the reconstructed plane |
| in order to generate smoother transparency gradients. |
| .TP |
| .B \-nodither |
| Disable all dithering (default). |
| .TP |
| .B \-mt |
| Use multi-threading for decoding, if possible. |
| .TP |
| .BI \-crop " x_position y_position width height |
| Crop the decoded picture to a rectangle with top-left corner at coordinates |
| (\fBx_position\fP, \fBy_position\fP) and size \fBwidth\fP x \fBheight\fP. |
| This cropping area must be fully contained within the source rectangle. |
| The top-left corner will be snapped to even coordinates if needed. |
| This option is meant to reduce the memory needed for cropping large images. |
| Note: the cropping is applied \fIbefore\fP any scaling. |
| .TP |
| .B \-flip |
| Flip decoded image vertically (can be useful for OpenGL textures for instance). |
| .TP |
| \fB\-resize\fR, \fB\-scale\fI width height\fR |
| Rescale the decoded picture to dimension \fBwidth\fP x \fBheight\fP. This |
| option is mostly intended to reducing the memory needed to decode large images, |
| when only a small version is needed (thumbnail, preview, etc.). Note: scaling |
| is applied \fIafter\fP cropping. |
| If either (but not both) of the \fBwidth\fP or \fBheight\fP parameters is 0, |
| the value will be calculated preserving the aspect-ratio. |
| .TP |
| .B \-quiet |
| Do not print anything. |
| .TP |
| .B \-v |
| Print extra information (decoding time in particular). |
| .TP |
| .B \-noasm |
| Disable all assembly optimizations. |
| |
| .SH BUGS |
| Please report all bugs to the issue tracker: |
| https://bugs.chromium.org/p/webp |
| .br |
| Patches welcome! See this page to get started: |
| http://www.webmproject.org/code/contribute/submitting-patches/ |
| |
| .SH EXAMPLES |
| dwebp picture.webp \-o output.png |
| .br |
| dwebp picture.webp \-ppm \-o output.ppm |
| .br |
| dwebp \-o output.ppm \-\- \-\-\-picture.webp |
| .br |
| cat picture.webp | dwebp \-o \- \-\- \- > output.ppm |
| |
| .SH AUTHORS |
| \fBdwebp\fP is a part of libwebp and was written by the WebP team. |
| .br |
| The latest source tree is available at |
| https://chromium.googlesource.com/webm/libwebp |
| .PP |
| This manual page was written by Pascal Massimino <pascal.massimino@gmail.com>, |
| for the Debian project (and may be used by others). |
| |
| .SH SEE ALSO |
| .BR cwebp (1), |
| .BR gif2webp (1), |
| .BR webpmux (1) |
| .br |
| Please refer to http://developers.google.com/speed/webp/ for additional |
| information. |
| .SS Output file format details |
| PAM: http://netpbm.sourceforge.net/doc/pam.html |
| .br |
| PGM: http://netpbm.sourceforge.net/doc/pgm.html |
| .br |
| PPM: http://netpbm.sourceforge.net/doc/ppm.html |
| .br |
| PNG: http://www.libpng.org/pub/png/png-sitemap.html#info |
