CWEBP(1)		    General Commands Manual		      CWEBP(1)

NAME
       cwebp - compress an image file to a WebP file

SYNOPSIS
       cwebp [options] input_file -o output_file.webp

DESCRIPTION
       This manual page documents the cwebp command.

       cwebp compresses an image using the WebP format.	 Input format can be
       either PNG, JPEG, TIFF, WebP or raw Y'CbCr samples.  Note: Animated PNG
       and WebP files are not supported.

OPTIONS
       The basic options are:

       -o string
	      Specify the name of the output WebP file. If omitted, cwebp will
	      perform compression but only report statistics.  Using "-" as
	      output name will direct output to 'stdout'.

       -- string
	      Explicitly specify the input file. This option is useful if the
	      input file starts with a '-' for instance. This option must
	      appear last.  Any other options afterward will be ignored.

       -h, -help
	      A short usage summary.

       -H, -longhelp
	      A summary of all the possible options.

       -version
	      Print the version number (as major.minor.revision) and exit.

       -lossless
	      Encode the image without any loss. For images with fully
	      transparent area, the invisible pixel values (R/G/B or Y/U/V)
	      will be preserved only if the -exact option is used.

       -near_lossless int
	      Specify the level of near-lossless image preprocessing. This
	      option adjusts pixel values to help compressibility, but has
	      minimal impact on the visual quality. It triggers lossless
	      compression mode automatically. The range is 0 (maximum
	      preprocessing) to 100 (no preprocessing, the default). The
	      typical value is around 60. Note that lossy with -q 100 can at
	      times yield better results.

       -q float
	      Specify the compression factor for RGB channels between 0 and
	      100. The default is 75.
	      In case of lossy compression (default), a small factor produces
	      a smaller file with lower quality. Best quality is achieved by
	      using a value of 100.
	      In case of lossless compression (specified by the -lossless
	      option), a small factor enables faster compression speed, but
	      produces a larger file.  Maximum compression is achieved by
	      using a value of 100.

       -z int Switch on lossless compression mode with the specified level
	      between 0 and 9, with level 0 being the fastest, 9 being the
	      slowest. Fast mode produces larger file size than slower ones. A
	      good default is -z 6.  This option is actually a shortcut for
	      some predefined settings for quality and method. If options -q
	      or -m are subsequently used, they will invalidate the effect of
	      this option.

       -alpha_q int
	      Specify the compression factor for alpha compression between 0
	      and 100.	Lossless compression of alpha is achieved using a
	      value of 100, while the lower values result in a lossy
	      compression. The default is 100.

       -preset string
	      Specify a set of pre-defined parameters to suit a particular
	      type of source material. Possible values are:  default, photo,
	      picture, drawing, icon, text. Since -preset overwrites the other
	      parameters' values (except the -q one), this option should
	      preferably appear first in the order of the arguments.

       -m int Specify the compression method to use. This parameter controls
	      the trade off between encoding speed and the compressed file
	      size and quality.	 Possible values range from 0 to 6. Default
	      value is 4.  When higher values are used, the encoder will spend
	      more time inspecting additional encoding possibilities and
	      decide on the quality gain.  Lower value can result in faster
	      processing time at the expense of larger file size and lower
	      compression quality.

       -crop x_position y_position width height
	      Crop the source to a rectangle with top-left corner at
	      coordinates (x_position, y_position) and size width x height.
	      This cropping area must be fully contained within the source
	      rectangle.  Note: the cropping is applied before any scaling.

       -resize width height
	      Resize the source to a rectangle with size width x height.  If
	      either (but not both) of the width or height parameters is 0,
	      the value will be calculated preserving the aspect-ratio. Note:
	      scaling is applied after cropping.

       -resize_mode string
	      Specify the behavior of the -resize option. Possible values are:
	      down_only, up_only, always (default). down_only will use the
	      values specified by -resize if either the input width or height
	      are larger than the given dimensions. Similarly, up_only will
	      only resize if either the input width or height are smaller than
	      the given dimensions.

       -mt    Use multi-threading for encoding, if possible.

       -low_memory
	      Reduce memory usage of lossy encoding by saving four times the
	      compressed size (typically). This will make the encoding slower
	      and the output slightly different in size and distortion. This
	      flag is only effective for methods 3 and up, and is off by
	      default. Note that leaving this flag off will have some side
	      effects on the bitstream: it forces certain bitstream features
	      like number of partitions (forced to 1). Note that a more
	      detailed report of bitstream size is printed by cwebp when using
	      this option.


   LOSSY OPTIONS
       These options are only effective when doing lossy encoding (the
       default, with or without alpha).


       -size int
	      Specify a target size (in bytes) to try and reach for the
	      compressed output.  The compressor will make several passes of
	      partial encoding in order to get as close as possible to this
	      target. If both -size and -psnr are used, -size value will
	      prevail.

       -psnr float
	      Specify a target PSNR (in dB) to try and reach for the
	      compressed output.  The compressor will make several passes of
	      partial encoding in order to get as close as possible to this
	      target. If both -size and -psnr are used, -size value will
	      prevail.

       -pass int
	      Set a maximum number of passes to use during the dichotomy used
	      by options -size or -psnr. Maximum value is 10, default is 1.
	      If options -size or -psnr were used, but -pass wasn't specified,
	      a default value of '6' passes will be used. If -pass is
	      specified, but neither -size nor -psnr are, a target PSNR of
	      40dB will be used.

       -qrange int int
	      Specifies the permissible interval for the quality factor. This
	      is particularly useful when using multi-pass (-size or -psnr
	      options).	 Default is 0 100.  If the quality factor is outside
	      this range, it will be clamped.  If the minimum value must be
	      less or equal to the maximum one.

       -af    Turns auto-filter on. This algorithm will spend additional time
	      optimizing the filtering strength to reach a well-balanced
	      quality.

       -jpeg_like
	      Change the internal parameter mapping to better match the
	      expected size of JPEG compression. This flag will generally
	      produce an output file of similar size to its JPEG equivalent
	      (for the same -q setting), but with less visual distortion.


       Advanced options:


       -f int Specify the strength of the deblocking filter, between 0 (no
	      filtering) and 100 (maximum filtering). A value of 0 will turn
	      off any filtering.  Higher value will increase the strength of
	      the filtering process applied after decoding the picture. The
	      higher the value the smoother the picture will appear. Typical
	      values are usually in the range of 20 to 50.

       -sharpness int
	      Specify the sharpness of the filtering (if used).	 Range is 0
	      (sharpest) to 7 (least sharp). Default is 0.

       -strong
	      Use strong filtering (if filtering is being used thanks to the
	      -f option). Strong filtering is on by default.

       -nostrong
	      Disable strong filtering (if filtering is being used thanks to
	      the -f option) and use simple filtering instead.

       -sharp_yuv
	      Use more accurate and sharper RGB->YUV conversion. Note that
	      this process is slower than the default 'fast' RGB->YUV
	      conversion.

       -sns int
	      Specify the amplitude of the spatial noise shaping. Spatial
	      noise shaping (or sns for short) refers to a general collection
	      of built-in algorithms used to decide which area of the picture
	      should use relatively less bits, and where else to better
	      transfer these bits. The possible range goes from 0 (algorithm
	      is off) to 100 (the maximal effect). The default value is 50.

       -segments int
	      Change the number of partitions to use during the segmentation
	      of the sns algorithm. Segments should be in range 1 to 4.
	      Default value is 4.  This option has no effect for methods 3 and
	      up, unless -low_memory is used.

       -partition_limit int
	      Degrade quality by limiting the number of bits used by some
	      macroblocks.  Range is 0 (no degradation, the default) to 100
	      (full degradation).  Useful values are usually around 30-70 for
	      moderately large images.	In the VP8 format, the so-called
	      control partition has a limit of 512k and is used to store the
	      following information: whether the macroblock is skipped, which
	      segment it belongs to, whether it is coded as intra 4x4 or intra
	      16x16 mode, and finally the prediction modes to use for each of
	      the sub-blocks.  For a very large image, 512k only leaves room
	      for a few bits per 16x16 macroblock.  The absolute minimum is 4
	      bits per macroblock. Skip, segment, and mode information can use
	      up almost all these 4 bits (although the case is unlikely),
	      which is problematic for very large images. The partition_limit
	      factor controls how frequently the most bit-costly mode (intra
	      4x4) will be used. This is useful in case the 512k limit is
	      reached and the following message is displayed: Error code: 6
	      (PARTITION0_OVERFLOW: Partition #0 is too big to fit 512k).  If
	      using -partition_limit is not enough to meet the 512k
	      constraint, one should use less segments in order to save more
	      header bits per macroblock.  See the -segments option. Note the
	      -m and -q options also influence the encoder's decisions and
	      ability to hit this limit.


   LOGGING OPTIONS
       These options control the level of output:

       -v     Print extra information (encoding time in particular).

       -print_psnr
	      Compute and report average PSNR (Peak-Signal-To-Noise ratio).

       -print_ssim
	      Compute and report average SSIM (structural similarity metric,
	      see https://en.wikipedia.org/wiki/SSIM for additional details).

       -print_lsim
	      Compute and report local similarity metric (sum of lowest error
	      amongst the collocated pixel neighbors).

       -progress
	      Report encoding progress in percent.

       -quiet Do not print anything.

       -short Only print brief information (output file size and PSNR) for
	      testing purposes.

       -map int
	      Output additional ASCII-map of encoding information. Possible
	      map values range from 1 to 6. This is only meant to help
	      debugging.


   ADDITIONAL OPTIONS
       More advanced options are:

       -s width height
	      Specify that the input file actually consists of raw Y'CbCr
	      samples following the ITU-R BT.601 recommendation, in 4:2:0
	      linear format.  The luma plane has size width x height.

       -pre int
	      Specify some preprocessing steps. Using a value of '2' will
	      trigger quality-dependent pseudo-random dithering during
	      RGBA->YUVA conversion (lossy compression only).

       -alpha_filter string
	      Specify the predictive filtering method for the alpha plane. One
	      of 'none', 'fast' or 'best', in increasing complexity and
	      slowness order. Default is 'fast'. Internally, alpha filtering
	      is performed using four possible predictions (none, horizontal,
	      vertical, gradient). The 'best' mode will try each mode in turn
	      and pick the one which gives the smaller size. The 'fast' mode
	      will just try to form an a priori guess without testing all
	      modes.

       -alpha_method int
	      Specify the algorithm used for alpha compression: 0 or 1.
	      Algorithm 0 denotes no compression, 1 uses WebP lossless format
	      for compression. The default is 1.

       -exact Preserve RGB values in transparent area. The default is off, to
	      help compressibility.

       -blend_alpha int
	      This option blends the alpha channel (if present) with the
	      source using the background color specified in hexadecimal as
	      0xrrggbb. The alpha channel is afterward reset to the opaque
	      value 255.

       -noalpha
	      Using this option will discard the alpha channel.

       -hint string
	      Specify the hint about input image type. Possible values are:
	      photo, picture or graph.

       -metadata string
	      A comma separated list of metadata to copy from the input to the
	      output if present.  Valid values: all, none, exif, icc, xmp.
	      The default is none.

	      Note: each input format may not support all combinations.

       -noasm Disable all assembly optimizations.


EXIT STATUS
       If there were no problems during execution, cwebp exits with the value
       of the C constant EXIT_SUCCESS. This is usually zero.

       If an error occurs, cwebp exits with the value of the C constant
       EXIT_FAILURE. This is usually one.


EXAMPLES
       cwebp -q 50 -lossless picture.png -o picture_lossless.webp
       cwebp -q 70 picture_with_alpha.png -o picture_with_alpha.webp
       cwebp -sns 70 -f 50 -size 60000 picture.png -o picture.webp
       cwebp -o picture.webp -- ---picture.png


AUTHORS
       cwebp is a part of libwebp and was written by the WebP team.
       The latest source tree is available at
       https://chromium.googlesource.com/webm/libwebp

       This manual page was written by Pascal Massimino
       <pascal.massimino@gmail.com>, for the Debian project (and may be used
       by others).


REPORTING BUGS
       Please report all bugs to the issue tracker:
       https://issues.webmproject.org
       Patches welcome! See this page to get started:
       https://www.webmproject.org/code/contribute/submitting-patches/


SEE ALSO
       dwebp(1), gif2webp(1)
       Please refer to https://developers.google.com/speed/webp/ for
       additional information.

				April 10, 2025			      CWEBP(1)