dwebp.1 (5098B)
1 .\" Hey, EMACS: -*- nroff -*- 2 .TH DWEBP 1 "July 18, 2024" 3 .SH NAME 4 dwebp \- decompress a WebP file to an image file 5 .SH SYNOPSIS 6 .B dwebp 7 .RI [ options ] " input_file.webp 8 .br 9 .SH DESCRIPTION 10 This manual page documents the 11 .B dwebp 12 command. 13 .PP 14 \fBdwebp\fP decompresses WebP files into PNG, PAM, PPM or PGM images. 15 Note: Animated WebP files are not supported. 16 .SH OPTIONS 17 The basic options are: 18 .TP 19 .B \-h 20 Print usage summary. 21 .TP 22 .B \-version 23 Print the version number (as major.minor.revision) and exit. 24 .TP 25 .BI \-o " string 26 Specify the name of the output file (as PNG format by default). 27 Using "-" as output name will direct output to 'stdout'. 28 .TP 29 .BI \-\- " string 30 Explicitly specify the input file. This option is useful if the input 31 file starts with an '\-' for instance. This option must appear \fBlast\fP. 32 Any other options afterward will be ignored. If the input file is "\-", 33 the data will be read from \fIstdin\fP instead of a file. 34 .TP 35 .B \-bmp 36 Change the output format to uncompressed BMP. 37 .TP 38 .B \-tiff 39 Change the output format to uncompressed TIFF. 40 .TP 41 .B \-pam 42 Change the output format to PAM (retains alpha). 43 .TP 44 .B \-ppm 45 Change the output format to PPM (discards alpha). 46 .TP 47 .B \-pgm 48 Change the output format to PGM. The output consists of luma/chroma 49 samples instead of RGB, using the IMC4 layout. This option is mainly 50 for verification and debugging purposes. 51 .TP 52 .B \-yuv 53 Change the output format to raw YUV. The output consists of 54 luma/chroma-U/chroma-V samples instead of RGB, saved sequentially as 55 individual planes. This option is mainly for verification and debugging 56 purposes. 57 .TP 58 .B \-nofancy 59 Don't use the fancy upscaler for YUV420. This may lead to jaggy 60 edges (especially the red ones), but should be faster. 61 .TP 62 .B \-nofilter 63 Don't use the in-loop filtering process even if it is required by 64 the bitstream. This may produce visible blocks on the non-compliant output, 65 but it will make the decoding faster. 66 .TP 67 .BI \-dither " strength 68 Specify a dithering \fBstrength\fP between 0 and 100. Dithering is a 69 post-processing effect applied to chroma components in lossy compression. 70 It helps by smoothing gradients and avoiding banding artifacts. 71 .TP 72 .BI \-alpha_dither 73 If the compressed file contains a transparency plane that was quantized 74 during compression, this flag will allow dithering the reconstructed plane 75 in order to generate smoother transparency gradients. 76 .TP 77 .B \-nodither 78 Disable all dithering (default). 79 .TP 80 .B \-mt 81 Use multi-threading for decoding, if possible. 82 .TP 83 .BI \-crop " x_position y_position width height 84 Crop the decoded picture to a rectangle with top-left corner at coordinates 85 (\fBx_position\fP, \fBy_position\fP) and size \fBwidth\fP x \fBheight\fP. 86 This cropping area must be fully contained within the source rectangle. 87 The top-left corner will be snapped to even coordinates if needed. 88 This option is meant to reduce the memory needed for cropping large images. 89 Note: the cropping is applied \fIbefore\fP any scaling. 90 .TP 91 .B \-flip 92 Flip decoded image vertically (can be useful for OpenGL textures for instance). 93 .TP 94 \fB\-resize\fR, \fB\-scale\fI width height\fR 95 Rescale the decoded picture to dimension \fBwidth\fP x \fBheight\fP. This 96 option is mostly intended to reducing the memory needed to decode large images, 97 when only a small version is needed (thumbnail, preview, etc.). Note: scaling 98 is applied \fIafter\fP cropping. 99 If either (but not both) of the \fBwidth\fP or \fBheight\fP parameters is 0, 100 the value will be calculated preserving the aspect-ratio. 101 .TP 102 .B \-quiet 103 Do not print anything. 104 .TP 105 .B \-v 106 Print extra information (decoding time in particular). 107 .TP 108 .B \-noasm 109 Disable all assembly optimizations. 110 111 .SH EXIT STATUS 112 If there were no problems during execution, \fBdwebp\fP exits with the value of 113 the C constant \fBEXIT_SUCCESS\fP. This is usually zero. 114 .PP 115 If an error occurs, \fBdwebp\fP exits with the value of the C constant 116 \fBEXIT_FAILURE\fP. This is usually one. 117 118 .SH EXAMPLES 119 dwebp picture.webp \-o output.png 120 .br 121 dwebp picture.webp \-ppm \-o output.ppm 122 .br 123 dwebp \-o output.ppm \-\- \-\-\-picture.webp 124 .br 125 cat picture.webp | dwebp \-o \- \-\- \- > output.ppm 126 127 .SH AUTHORS 128 \fBdwebp\fP is a part of libwebp and was written by the WebP team. 129 .br 130 The latest source tree is available at 131 https://chromium.googlesource.com/webm/libwebp 132 .PP 133 This manual page was written by Pascal Massimino <pascal.massimino@gmail.com>, 134 for the Debian project (and may be used by others). 135 136 .SH REPORTING BUGS 137 Please report all bugs to the issue tracker: 138 https://issues.webmproject.org 139 .br 140 Patches welcome! See this page to get started: 141 https://www.webmproject.org/code/contribute/submitting\-patches/ 142 143 .SH SEE ALSO 144 .BR cwebp (1), 145 .BR gif2webp (1), 146 .BR webpmux (1) 147 .br 148 Please refer to https://developers.google.com/speed/webp/ for additional 149 information. 150 .SS Output file format details 151 PAM: http://netpbm.sourceforge.net/doc/pam.html 152 .br 153 PGM: http://netpbm.sourceforge.net/doc/pgm.html 154 .br 155 PPM: http://netpbm.sourceforge.net/doc/ppm.html 156 .br 157 PNG: http://www.libpng.org/pub/png/png-sitemap.html#info