@nwrks/webp-converter

4mCWEBP24m(1) General Commands Manual 4mCWEBP24m(1) 1mNAME0m cwebp - compress an image file to a WebP file 1mSYNOPSIS0m 1mcwebp 22m[4moptions24m] 4minput_file24m 4m-o24m 4moutput_file.webp0m 1mDESCRIPTION0m This manual page documents the 1mcwebp 22mcommand. 1mcwebp 22mcompresses 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. 1mOPTIONS0m The basic options are: 1m-o 4m22mstring0m Specify the name of the output WebP file. If omitted, 1mcwebp 22mwill perform compression but only report statistics. Using "-" as output name will direct output to 'stdout'. 1m-- 4m22mstring0m Explicitly specify the input file. This option is useful if the input file starts with a '-' for instance. This option must ap- pear 1mlast22m. Any other options afterward will be ignored. 1m-h, -help0m A short usage summary. 1m-H, -longhelp0m A summary of all the possible options. 1m-version0m Print the version number (as major.minor.revision) and exit. 1m-lossless0m Encode the image without any loss. For images with fully trans- parent area, the invisible pixel values (R/G/B or Y/U/V) will be preserved only if the -exact option is used. 1m-near_lossless 4m22mint0m Specify the level of near-lossless image preprocessing. This op- tion adjusts pixel values to help compressibility, but has mini- mal impact on the visual quality. It triggers lossless compres- sion mode automatically. The range is 0 (maximum preprocessing) to 100 (no preprocessing, the default). The typical value is around 60. Note that lossy with 1m-q 100 22mcan at times yield better results. 1m-q 4m22mfloat0m 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 1m-lossless 22mop- tion), a small factor enables faster compression speed, but pro- duces a larger file. Maximum compression is achieved by using a value of 100. 1m-z 4m22mint24m Switch on 1mlossless 22mcompression mode with the specified level be- tween 0 and 9, with level 0 being the fastest, 9 being the slow- est. Fast mode produces larger file size than slower ones. A good default is 1m-z 622m. This option is actually a shortcut for some predefined settings for quality and method. If options 1m-q0m or 1m-m 22mare subsequently used, they will invalidate the effect of this option. 1m-alpha_q 4m22mint0m 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 compres- sion. The default is 100. 1m-preset 4m22mstring0m Specify a set of pre-defined parameters to suit a particular type of source material. Possible values are: 1mdefault22m, 1mphoto22m, 1mpicture22m, 1mdrawing22m, 1micon22m, 1mtext22m. Since 1m-preset 22moverwrites the other parameters' values (except the 1m-q 22mone), this option should preferably appear first in the order of the arguments. 1m-m 4m22mint24m 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 de- cide on the quality gain. Lower value can result in faster pro- cessing time at the expense of larger file size and lower com- pression quality. 1m-crop 4m22mx_position24m 4my_position24m 4mwidth24m 4mheight0m Crop the source to a rectangle with top-left corner at coordi- nates (1mx_position22m, 1my_position22m) and size 1mwidth 22mx 1mheight22m. This cropping area must be fully contained within the source rectan- gle. Note: the cropping is applied 4mbefore24m any scaling. 1m-resize 4m22mwidth24m 4mheight0m Resize the source to a rectangle with size 1mwidth 22mx 1mheight22m. If either (but not both) of the 1mwidth 22mor 1mheight 22mparameters is 0, the value will be calculated preserving the aspect-ratio. Note: scaling is applied 4mafter24m cropping. 1m-mt 22mUse multi-threading for encoding, if possible. 1m-low_memory0m 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 de- fault. Note that leaving this flag off will have some side ef- fects on the bitstream: it forces certain bitstream features like number of partitions (forced to 1). Note that a more de- tailed report of bitstream size is printed by 1mcwebp 22mwhen using this option. 1mLOSSY OPTIONS0m These options are only effective when doing lossy encoding (the de- fault, with or without alpha). 1m-size 4m22mint0m Specify a target size (in bytes) to try and reach for the com- pressed output. The compressor will make several passes of par- tial encoding in order to get as close as possible to this tar- get. If both 1m-size 22mand 1m-psnr 22mare used, 1m-size 22mvalue will prevail. 1m-psnr 4m22mfloat0m Specify a target PSNR (in dB) to try and reach for the com- pressed output. The compressor will make several passes of par- tial encoding in order to get as close as possible to this tar- get. If both 1m-size 22mand 1m-psnr 22mare used, 1m-size 22mvalue will prevail. 1m-pass 4m22mint0m Set a maximum number of passes to use during the dichotomy used by options 1m-size 22mor 1m-psnr22m. Maximum value is 10, default is 1. If options 1m-size 22mor 1m-psnr 22mwere used, but 1m-pass 22mwasn't specified, a default value of '6' passes will be used. If 1m-pass 22mis speci- fied, but neither 1m-size 22mnor 1m-psnr 22mare, a target PSNR of 40dB will be used. 1m-qrange 4m22mint24m 4mint0m Specifies the permissible interval for the quality factor. This is particularly useful when using multi-pass (1m-size 22mor 1m-psnr 22mop- tions). 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. 1m-af 22mTurns auto-filter on. This algorithm will spend additional time optimizing the filtering strength to reach a well-balanced qual- ity. 1m-jpeg_like0m Change the internal parameter mapping to better match the ex- pected size of JPEG compression. This flag will generally pro- duce an output file of similar size to its JPEG equivalent (for the same 1m-q 22msetting), but with less visual distortion. Advanced options: 1m-f 4m22mint24m 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. 1m-sharpness 4m22mint0m Specify the sharpness of the filtering (if used). Range is 0 (sharpest) to 7 (least sharp). Default is 0. 1m-strong0m Use strong filtering (if filtering is being used thanks to the 1m-f 22moption). Strong filtering is on by default. 1m-nostrong0m Disable strong filtering (if filtering is being used thanks to the 1m-f 22moption) and use simple filtering instead. 1m-sharp_yuv0m Use more accurate and sharper RGB->YUV conversion if needed. Note that this process is slower than the default 'fast' RGB->YUV conversion. 1m-sns 4m22mint0m Specify the amplitude of the spatial noise shaping. Spatial noise shaping (or 1msns 22mfor 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 trans- fer these bits. The possible range goes from 0 (algorithm is off) to 100 (the maximal effect). The default value is 50. 1m-segments 4m22mint0m Change the number of partitions to use during the segmentation of the sns algorithm. Segments should be in range 1 to 4. De- fault value is 4. This option has no effect for methods 3 and up, unless 1m-low_memory 22mis used. 1m-partition_limit 4m22mint0m Degrade quality by limiting the number of bits used by some mac- roblocks. Range is 0 (no degradation, the default) to 100 (full degradation). Useful values are usually around 30-70 for moder- ately 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: 4mError24m 4mcode:24m 4m624m 4m(PARTI-0m 4mTION0_OVERFLOW:24m 4mPartition24m 4m#024m 4mis24m 4mtoo24m 4mbig24m 4mto24m 4mfit24m 4m512k)24m. If using 1m-partition_limit 22mis not enough to meet the 512k constraint, one should use less segments in order to save more header bits per macroblock. See the 1m-segments 22moption. Note the 1m-m 22mand 1m-q 22mop- tions also influence the encoder's decisions and ability to hit this limit. 1mLOGGING OPTIONS0m These options control the level of output: 1m-v 22mPrint extra information (encoding time in particular). 1m-print_psnr0m Compute and report average PSNR (Peak-Signal-To-Noise ratio). 1m-print_ssim0m Compute and report average SSIM (structural similarity metric, see https://en.wikipedia.org/wiki/SSIM for additional details). 1m-print_lsim0m Compute and report local similarity metric (sum of lowest error amongst the collocated pixel neighbors). 1m-progress0m Report encoding progress in percent. 1m-quiet 22mDo not print anything. 1m-short 22mOnly print brief information (output file size and PSNR) for testing purposes. 1m-map 4m22mint0m Output additional ASCII-map of encoding information. Possible map values range from 1 to 6. This is only meant to help debug- ging. 1mADDITIONAL OPTIONS0m More advanced options are: 1m-s 4m22mwidth24m 4mheight0m Specify that the input file actually consists of raw Y'CbCr sam- ples following the ITU-R BT.601 recommendation, in 4:2:0 linear format. The luma plane has size 1mwidth 22mx 1mheight22m. 1m-pre 4m22mint0m Specify some preprocessing steps. Using a value of '2' will trigger quality-dependent pseudo-random dithering during RGBA->YUVA conversion (lossy compression only). 1m-alpha_filter 4m22mstring0m Specify the predictive filtering method for the alpha plane. One of 'none', 'fast' or 'best', in increasing complexity and slow- ness 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. 1m-alpha_method 4m22mint0m Specify the algorithm used for alpha compression: 0 or 1. Algo- rithm 0 denotes no compression, 1 uses WebP lossless format for compression. The default is 1. 1m-exact 22mPreserve RGB values in transparent area. The default is off, to help compressibility. 1m-blend_alpha 4m22mint0m 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. 1m-noalpha0m Using this option will discard the alpha channel. 1m-hint 4m22mstring0m Specify the hint about input image type. Possible values are: 1mphoto22m, 1mpicture 22mor 1mgraph22m. 1m-metadata 4m22mstring0m A comma separated list of metadata to copy from the input to the output if present. Valid values: 1mall22m, 1mnone22m, 1mexif22m, 1micc22m, 1mxmp22m. The default is 1mnone22m. Note: each input format may not support all combinations. 1m-noasm 22mDisable all assembly optimizations. 1mBUGS0m Please report all bugs to the issue tracker: https://bugs.chromium.org/p/webp Patches welcome! See this page to get started: https://www.webmpro- ject.org/code/contribute/submitting-patches/ 1mEXAMPLES0m 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 1mAUTHORS0m 1mcwebp 22mis a part of libwebp and was written by the WebP team. The latest source tree is available at https://chromium.google- source.com/webm/libwebp This manual page was written by Pascal Massimino <pascal.mas- simino@gmail.com>, for the Debian project (and may be used by others). 1mSEE ALSO0m 1mdwebp22m(1), 1mgif2webp22m(1) Please refer to https://developers.google.com/speed/webp/ for addi- tional information. March 26, 2024 4mCWEBP24m(1)