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87-581: WebP is a raster graphics file format developed by Google intended as a replacement for JPEG , PNG , and GIF file formats. It supports both lossy and lossless compression, as well as animation and alpha transparency . Google announced the WebP format in September 2010, and released the first stable version of its supporting library in April 2018. WebP was first announced by Google on 30 September in 2010 as

174-513: A flag or switch ) modifies the operation of a command; the effect is determined by the command's program. Options follow the command name on the command line, separated by spaces. A space before the first option is not always required, such as Dir/? and DIR /? in DOS, which have the same effect of listing the DIR command's available options, whereas dir --help (in many versions of Unix) does require

261-507: A help option provides a concise review of the options of a command. The command-line environment may not provide graphical enhancements such as different fonts or extended edit windows found in a GUI. It may be difficult for a new user to become familiar with all the commands and options available, compared with the icons and drop-down menus of a graphical user interface, without reference to manuals. Operating system (OS) command-line interfaces are usually distinct programs supplied with

348-422: A luminance–chrominance model with chroma subsampling by a ratio of 1:2 ( YCbCr 4:2:0). Without further content, the mandatory RIFF container has an overhead of only twenty bytes, though it can also hold additional metadata. The side length of WebP images is limited to 16 383 pixels. WebP is based on block prediction. Each block is predicted on the values from the three blocks above it and from one block to

435-474: A pipeline where the output of one command becomes the input to the next command. One can modify the set of available commands by modifying which paths appear in the PATH environment variable. Under Unix, commands also need be marked as executable files. The directories in the path variable are searched in the order they are given. By re-ordering the path, one can run e.g. \OS2\MDOS\E.EXE instead of \OS2\E.EXE, when

522-478: A "playground for image compression experiments". Raster graphics The printing and prepress industries know raster graphics as contones (from continuous tones ). In contrast, line art is usually implemented as vector graphics in digital systems. Many raster manipulations map directly onto the mathematical formalisms of linear algebra , where mathematical objects of matrix structure are of central concern. The word "raster" has its origins in

609-423: A 19% reduction is achieved as reported by Google, although real world performance is nearer to 10%. Google actively promotes WebP, and Google Chrome and all Chromium -based browsers support the format. The proprietary PageSpeed Insights tool suggests that webmasters switch from JPEG and PNG to WebP in order to improve their website speed score. Microsoft Edge versions released after January 2020 are based on

696-597: A 45% reduction in file size when starting with PNGs found on the web, and a 28% reduction compared to PNGs that are recompressed with pngcrush and PNGOUT . In July 2016, Apple added WebP support to early beta versions of macOS Sierra and iOS 10, but support was later removed in the GM seed versions of iOS 10 and macOS Sierra released in September 2016. In September 2020, WebP support was added in Safari version 14. The supporting libwebp library reached version 1.0 in April 2018. In 2019,

783-438: A CLI, presenting their own prompt to the user and accepting command lines. Other programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file . In other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality. For example, all features of MATLAB , a numerical analysis computer program, are available via

870-453: A Unix-like CLI. Microsoft provides MKS Inc. 's ksh implementation MKS Korn shell for Windows through their Services for UNIX add-on. Since 2001, the Macintosh operating system macOS has been based on a Unix-like operating system called Darwin . On these computers, users can access a Unix-like command-line interface by running the terminal emulator program called Terminal , which

957-417: A color cache of recently used colors. This complements basic techniques such as dictionary coding , Huffman coding and color indexing transform. This format uses a recursive definition: all of the control images, such as the local entropy code selection, are encoded the same way as the whole image itself. Google has proposed using WebP for animated images as an alternative to the popular GIF format, citing

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1044-504: A command procedure or script which itself can be treated as a command. These advantages mean that a user must figure out a complex command or series of commands only once, because they can be saved, to be used again. The commands given to a CLI shell are often in one of the following forms: where doSomething is, in effect, a verb , how an adverb (for example, should the command be executed verbosely or quietly ) and toFiles an object or objects (typically one or more files) on which

1131-551: A comprehensive study of current lossy encoding techniques and was not able to conclude that WebP outperformed mozjpeg by any significant margin. In September 2023, two critical vulnerabilities relating to WebP images were discovered by Apple Security Engineering and Architecture (SEAR) and the Citizen Lab, potentially affecting Google Chrome, Chromium-based browsers and the libwebp project from Google, among any application implementing libwebp. Among these vulnerabilities, CVE-2023-4863

1218-664: A free plug-in that enables WebP support in earlier versions of Adobe Photoshop . Free Photoshop plug-ins had been released by Telegraphics and fnordware before that. GIMP up to version 2.8 also supported WebP via a plugin; later, this plugin was shipped in GIMP 2.9 branch, and received multiple improvements. Google has also released a plug-in for Microsoft Windows that enables WebP support in Windows Photo Viewer , Microsoft Office 2010 , FastPictureViewer , and any other application that uses Windows Imaging Component . FFmpeg linked with

1305-608: A major patching challenge to mitigate the vulnerability due to the demanding testing requirements before release, highlighting the implications of this vulnerability on a wide scale. Google has been developing the second version of WebP since June 2021. Its reference implementation is libwebp2 . The main goal of this new format is to reach similar compression ratios as AVIF while remaining faster to encode and decode. On 12 October 2022, Google changed WebP 2's development repository's README file to state that "WebP 2 will not be released as an image format" and began describing WebP 2 as

1392-772: A new open format for lossy compressed true-color graphics on the web, producing files that were smaller than JPEG files for comparable image quality. It was based on technology which Google had acquired with the purchase of On2 Technologies . As a derivative of the VP8 video format, it is a sister project to the WebM multimedia container format. WebP-related software is released under a BSD free software license . On 3 October 2011, Google added an "Extended File Format" allowing WebP support for animation , ICC profile , XMP and Exif metadata , and tiling (compositing very large images from maximum 16 384  ×  16 384 tiles). Tiling support

1479-425: A printer setting of 1200 DPI. Raster-based image editors, such as PaintShop Pro , Corel Painter , Adobe Photoshop , Paint.NET , Microsoft Paint , Krita , and GIMP , revolve around editing pixels , unlike vector-based image editors, such as Xfig , CorelDRAW , Adobe Illustrator , or Inkscape , which revolve around editing lines and shapes ( vectors ). When an image is rendered in a raster-based image editor,

1566-588: A pure GUI. This is typically the case with operating system command shells . CLIs are also used by systems with insufficient resources to support a graphical user interface. Some computer language systems (such as Python , Forth , LISP , Rexx , and many dialects of BASIC ) provide an interactive command-line mode to allow for rapid evaluation of code. CLIs are often used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users. CLIs are also popular among people with visual disabilities since

1653-423: A raster approach. Each on-screen pixel directly corresponds to a small number of bits in memory. The screen is refreshed simply by scanning through pixels and coloring them according to each set of bits. The refresh procedure, being speed critical, is often implemented by dedicated circuitry, often as a part of a graphics processing unit . Using this approach, the computer contains an area of memory that holds all

1740-399: A very different meaning, and this can be misleading. Because, through the dithering process, the printer builds a single image pixel out of several printer dots to increase color depth , the printer's DPI setting must be set far higher than the desired PPI to ensure sufficient color depth without sacrificing image resolution. Thus, for instance, printing an image at 250 PPI may actually require

1827-417: Is achieved using Flash . Support for WebP was added to Links in version 2.26. At the announcement of WebP in September 2010, no graphics software supported WebP. By 2011, there were plugins for several popular graphics software programs to support WebP, and some programs such as Acorn and Pixelmator had added native support. Over time, support for the WebP format has grown. In 2019, Google released

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1914-509: Is active a program is typically invoked by typing its name followed by command-line arguments (if any). For example, in Unix and Unix-like environments, an example of a command-line argument is: file.s is a command-line argument which tells the program rm to remove the file named file.s . Some programming languages, such as C , C++ and Java , allow a program to interpret the command-line arguments by handling them as string parameters in

2001-402: Is based on a (usually rectangular, square-based) tessellation of the 2D plane into cells, each containing a single value. To store the data in a file, the two-dimensional array must be serialized. The most common way to do this is a row-major format, in which the cells along the first (usually top) row are listed left to right, followed immediately by those of the second row, and so on. In

2088-457: Is compressed with entropy encoding . WebP also has explicit support for parallel decoding. The reference implementation consists of converter software in the form of a command-line program for Linux (cwebp) and a programming library for the decoding, the same as for WebM. The open-source community ported the converter to other platforms, such as Windows. The WebP container (i.e., RIFF container for WebP) allows feature support over and above

2175-584: Is found in the Utilities sub-folder of the Applications folder, or by remotely logging into the machine using ssh . Z shell is the default shell for macOS; Bash, tcsh , and the KornShell are also provided. Before macOS Catalina , Bash was the default. A CLI is used whenever a large vocabulary of commands or queries, coupled with a wide (or arbitrary) range of options, can be entered more rapidly as text than with

2262-460: Is lost, although certain vectorization operations can recreate salient information, as in the case of optical character recognition . Early mechanical televisions developed in the 1920s employed rasterization principles. Electronic television based on cathode-ray tube displays are raster scanned with horizontal rasters painted left to right, and the raster lines painted top to bottom. Modern flat-panel displays such as LED monitors still use

2349-516: Is the grammar that all commands must follow. In the case of operating systems , DOS and Unix each define their own set of rules that all commands must follow. In the case of embedded systems , each vendor, such as Nortel , Juniper Networks or Cisco Systems , defines their own proprietary set of rules. These rules also dictate how a user navigates through the system of commands. The semantics define what sort of operations are possible, on what sort of data these operations can be performed, and how

2436-506: Is vector, rendering specifications and software such as PostScript are used to create the raster image. Three-dimensional voxel raster graphics are employed in video games and are also used in medical imaging such as MRI scanners . Geographic phenomena are commonly represented in a raster format in GIS . The raster grid is georeferenced , so that each pixel (commonly called a cell in GIS because

2523-644: The Alliance for Open Media published the AVIF standard, intending it to be a successor to WebP. As of 2024, web browsers that support WebP had 97% market share. WebP's lossy compression algorithm is based on the intra-frame coding of the VP8 video format and the Resource Interchange File Format (RIFF) as a container format . As such, it is a block-based transformation scheme with eight bits of color depth and

2610-662: The Exif standard. High-resolution raster grids contain a large number of pixels, and thus consume a large amount of memory. This has led to multiple approaches to compressing the data volume into smaller files. The most common strategy is to look for patterns or trends in the pixel values, then store a parameterized form of the pattern instead of the original data. Common raster compression algorithms include run-length encoding (RLE), JPEG , LZ (the basis for PNG and ZIP ), Lempel–Ziv–Welch (LZW) (the basis for GIF ), and others. For example, Run length encoding looks for repeated values in

2697-476: The main function . Other languages, such as Python , expose operating system specific API (functionality) through sys module , and in particular sys.argv for command-line arguments . In Unix-like operating systems , a single hyphen used in place of a file name is a special value specifying that a program should handle data coming from the standard input or send data to the standard output . A command-line option or simply option (also known as

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2784-510: The resolution or support , is constant across the grid. Raster or gridded data may be the result of a gridding procedure. A single numeric value is then stored for each pixel. For most images, this value is a visible color, but other measurements are possible, even numeric codes for qualitative categories. Each raster grid has a specified pixel format , the data type for each number. Common pixel formats are binary , gray-scale , palettized , and full-color , where color depth determines

2871-597: The visible spectrum ; the large CCD bitmapped sensor at the Vera C. Rubin Observatory captures 3.2 gigapixels in a single image (6.4 GB raw), over six color channels which exceed the spectral range of human color vision. Most computer images are stored in raster graphics formats or compressed variations, including GIF , JPEG , and PNG , which are popular on the World Wide Web . A raster data structure

2958-446: The "picture" part of "pixel" is not relevant) represents a square region of geographic space. The value of each cell then represents some measurable ( qualitative or quantitative ) property of that region, typically conceptualized as a field . Examples of fields commonly represented in rasters include: temperature, population density, soil moisture, land cover, surface elevation, etc. Two sampling models are used to derive cell values from

3045-524: The CLI, whereas the MATLAB GUI exposes only a subset of features. In Colossal Cave Adventure from 1975, the user uses a CLI to enter one or two words to explore a cave system. The command-line interface evolved from a form of communication conducted by people over teleprinter (TTY) machines. Sometimes these involved sending an order or a confirmation using telex . Early computer systems often used teleprinter as

3132-494: The Chromium browser, and have native WebP support. EdgeHTML -based versions of Microsoft Edge support WebP through a platform extension (installed by default) (unless running in the security-hardened "Application Guard" mode, which does not support platform extensions). Safari added support for WebP in 2020 with iOS 14 and macOS Big Sur . Mozilla Firefox (and its fork Waterfox ) officially supports WebP since January 2019. It

3219-506: The Latin rastrum (a rake), which is derived from radere (to scrape). It originates from the raster scan of cathode-ray tube (CRT) video monitors , which draw the image line by line by magnetically or electrostatically steering a focused electron beam . By association, it can also refer to a rectangular grid of pixels. The word rastrum is now used to refer to a device for drawing musical staff lines. The fundamental strategy underlying

3306-735: The LibreOffice technology based online office Collabora Online . Godot Engine as of version 4.0 supports importing and exporting WebP images and uses WebP as its internal format for storing imported compressed textures. Content management systems (CMS) usually do not support WebP natively or by default. However, for most popular CMS, extensions are available for automated conversion from other image formats to WebP and delivering WebP images to compatible browsers. Since June 2021, WordPress supports WebP natively. Social media services known to natively support WebP in messages, include Facebook , Slack , Discord and Element , but as of 2 October 2024

3393-515: The PC's serial ports . These were typically used to interface an organization's new PC's with their existing mini- or mainframe computers, or to connect PC to PC. Some of these PCs were running Bulletin Board System software. Early operating system CLIs were implemented as part of resident monitor programs, and could not easily be replaced. The first implementation of the shell as a replaceable component

3480-693: The VP8/VP9 reference codec library libvpx can extract VP8 key frames from WebM media and a script can then add the WebP RIFF header and the NUL pad byte for odd frame lengths. Meanwhile, FFmpeg supports libwebp directly. Gmail and Google Photos both support WebP. Support for WebP is also planned for Google App Engine . The Instant Previews feature of Google Search uses WebP internally to reduce disk space used by previews. Android 4.0 supports encoding and decoding WebP images (via bitmap and Skia ). SDL_image supports

3567-492: The Windows CMD.EXE programs, the latter groups being based heavily on DEC's RSX-11 and RSTS CLIs. Under most operating systems, it is possible to replace the default shell program with alternatives; examples include 4DOS for DOS, 4OS2 for OS/2, and 4NT / Take Command for Windows. Although the term 'shell' is often used to describe a command-line interpreter, strictly speaking, a 'shell' can be any program that constitutes

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3654-402: The advantages of 24-bit color with transparency, combining frames with lossy and lossless compression in the same animation, and support for seeking to specific frames. Google reports a 64% reduction in file size for images converted from animated GIFs to lossy WebP, however, with a very noticeable visual impact, both at default settings, and optimised settings. When converting using lossless WebP,

3741-500: The array, and replaces them with the value and the number of times it appears. Thus, the raster above would be represented as: This technique is very efficient when there are large areas of identical values, such as a line drawing, but in a photograph where pixels are usually slightly different from their neighbors, the RLE file would be up to twice the size of the original. Some compression algorithms, such as RLE and LZW, are lossless , where

3828-422: The basic use case of WebP (i.e., a file containing a single image encoded as a VP8 key frame). The WebP container provides additional support for: WebP's lossless compression, a newer algorithm unrelated to VP8, was designed by Google software engineer Jyrki Alakuijala. It uses advanced techniques such as dedicated entropy codes for different color channels, exploiting 2D locality of backward reference distances and

3915-423: The command In zsh the $ RPROMPT variable controls an optional prompt on the right-hand side of the display. It is not a real prompt in that the location of text entry does not change. It is used to display information on the same line as the prompt, but right-justified. In RISC OS the command prompt is a * symbol, and thus (OS) CLI commands are often referred to as star commands . One can also access

4002-660: The command line interface as the primary user interface replaced by the Graphical User Interface . The command line remained available as an alternative user interface, often used by system administrators and other advanced users for system administration, computer programming and batch processing . In November 2006, Microsoft released version 1.0 of Windows PowerShell (formerly codenamed Monad ), which combined features of traditional Unix shells with their proprietary object-oriented .NET Framework . MinGW and Cygwin are open-source packages for Windows that offer

4089-399: The command should act. The > in the third example is a redirection operator , telling the command-line interpreter to send the output of the command not to its own standard output (the screen) but to the named file. This will overwrite the file. Using >> will redirect the output and append it to the file. Another redirection operator is the vertical bar ( | ), which creates

4176-431: The commands and responses can be displayed using refreshable Braille displays . The general pattern of a command line interface is: In this format, the delimiters between command-line elements are whitespace characters and the end-of-line delimiter is the newline delimiter. This is a widely used (but not universal) convention. A CLI can generally be considered as consisting of syntax and semantics . The syntax

4263-466: The commands. Alternatives to CLIs include GUIs (most notably desktop metaphors with a mouse pointer , such as Microsoft Windows ), text-based user interface menus (such as DOS Shell and IBM AIX SMIT ), and keyboard shortcuts . Compared with a graphical user interface, a command-line interface requires fewer system resources to implement. Since options to commands are given in a few characters in each command line, an experienced user often finds

4350-404: The complexity of the compression, it is also significantly slower than other web image formats. It is therefore usually not advisable to process the images directly, as is the case with Web Map Services . In September 2010, Fiona Glaser, a developer of the x264 encoder, wrote a very early critique of WebP. Comparing different encodings (JPEG, x264, and WebP) of a reference image, she stated that

4437-407: The current time, user, shell number or working directory) in order, for instance, to make the prompt more informative or visually pleasing, to distinguish sessions on various machines, or to indicate the current level of nesting of commands. On some systems, special tokens in the definition of the prompt can be used to cause external programs to be called by the command-line interpreter while displaying

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4524-472: The data that are to be displayed. The central processor writes data into this region of memory and the video controller collects them from there. The bits of data stored in this block of memory are related to the eventual pattern of pixels that will be used to construct an image on the display. An early scanned display with raster computer graphics was invented in the late 1960s by A. Michael Noll at Bell Labs , but its patent application filed February 5, 1970,

4611-422: The default is the opposite. Renaming of the executables also works: people often rename their favourite editor to EDIT, for example. The command line allows one to restrict available commands, such as access to advanced internal commands. The Windows CMD.EXE does this. Often, shareware programs will limit the range of commands, including printing a command 'your administrator has disabled running batch files' from

4698-478: The example at right, the cells of tessellation A are overlaid on the point pattern B resulting in an array C of quadrant counts representing the number of points in each cell. For purposes of visualization a lookup table has been used to color each of the cells in an image D. Here are the numbers as a serial row-major array: 1 3 0 0 1 12 8 0 1 4 3 3 0 2 0 2 1 7 4 1 5 4 2 2 0 3 1 2 2 2 2 3 0 5 1 9 3 3 3 4 5 0 8 0 2 4 3 2 8 4 3 2 2 7 2 3 2 10 1 5 2 1 3 7 To reconstruct

4785-494: The features that are commonly considered to produce structured programs. The Bourne shell led to the development of the KornShell (ksh), Almquist shell (ash), and the popular Bourne-again shell (or Bash). Early microcomputers themselves were based on a command-line interface such as CP/M , DOS or AppleSoft BASIC . During the 1980s and 1990s, the introduction of the Apple Macintosh and of Microsoft Windows on PCs saw

4872-468: The fidelity of the colors represented, and color space determines the range of color coverage (which is often less than the full range of human color vision ). Most modern color raster formats represent color using 24 bits (over 16 million distinct colors), with 8 bits (values 0–255) for each color channel (red, green, and blue). The digital sensors used for remote sensing and astronomy are often able to detect and store wavelengths beyond

4959-407: The field: in a lattice , the value is measured at the center point of each cell; in a grid , the value is a summary (usually a mean or mode) of the value over the entire cell. Raster graphics are resolution dependent, meaning they cannot scale up to an arbitrary resolution without loss of apparent quality . This property contrasts with the capabilities of vector graphics , which easily scale up to

5046-500: The first Multics shell was developed by Glenda Schroeder . The first Unix shell , the V6 shell , was developed by Ken Thompson in 1971 at Bell Labs and was modeled after Schroeder's Multics shell. The Bourne shell was introduced in 1977 as a replacement for the V6 shell. Although it is used as an interactive command interpreter, it was also intended as a scripting language and contains most of

5133-411: The format since 1.2.11. Sumatra PDF supports WebP images for both standalone files and comic books since version 2.4. Telegram Messenger uses WebP for its Stickers, claiming they are displayed five times faster compared to the other formats usually used in messaging apps. Signal uses WebP for its non-animated stickers. LibreOffice supports the import of WebP images since version 7.4, so does

5220-412: The grammar represents these operations and data—the symbolic meaning in the syntax. Two different CLIs may agree on either syntax or semantics, but it is only when they agree on both that they can be considered sufficiently similar to allow users to use both CLIs without needing to learn anything, as well as to enable re-use of scripts. A simple CLI will display a prompt, accept a command line typed by

5307-575: The image is composed of millions of pixels. At its core, a raster image editor works by manipulating each individual pixel. Most pixel-based image editors work using the RGB color model , but some also allow the use of other color models such as the CMYK color model . Command-line interface A command-line interface ( CLI ) is a means of interacting with a computer program by inputting lines of text called command-lines . Command-line interfaces emerged in

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5394-501: The interface mode. At this point, commands from the system mode may not be accessible until the user exits the interface mode and enters the system mode. A command prompt (or just prompt ) is a sequence of (one or more) characters used in a command-line interface to indicate readiness to accept commands. It literally prompts the user to take action. A prompt usually ends with one of the characters $ , % , # , : , > or - and often includes other information, such as

5481-459: The latter only support static WebP, and not animated WebP. Like VP8 on which it is based, former lossy WebP supports only 8-bit YUV 4:2:0 format, which may cause color loss on images with thin contrast elements (such as in pixel art and computer graphics ) and ghosting in anaglyph . To overcome this restriction, new lossless WebP supports VP8L encoding that works exclusively with 8-bit RGBA (red, green, blue, alpha) color space. However, due to

5568-439: The left of it (block decoding is done in raster-scan order: left to right and top to bottom). There are four basic modes of block prediction: horizontal, vertical, DC (one color), and TrueMotion. Mispredicted data and non-predicted blocks are compressed in a 4×4 pixel sub-block with a discrete cosine transform or a Walsh–Hadamard transform . Both transforms are done with fixed-point arithmetic to avoid rounding errors. The output

5655-598: The means of interaction with an operator. The mechanical teleprinter was replaced by a "glass tty" , a keyboard and screen emulating the teleprinter. "Smart" terminals permitted additional functions, such as cursor movement over the entire screen, or local editing of data on the terminal for transmission to the computer. As the microcomputer revolution replaced the traditional – minicomputer + terminals – time sharing architecture, hardware terminals were replaced by terminal emulators  — PC software that interpreted terminal signals sent through

5742-706: The mid-1960s, on computer terminals , as an interactive and more user-friendly alternative to the non-interactive interface available with punched cards . Today, most computer users rely on graphical user interfaces ("GUIs") instead of CLIs. However, many programs and operating system utilities lack GUIs, and are intended to be used through CLIs. Knowledge of CLIs is also useful for writing scripts . Programs that have CLIs are generally easy to automate via scripting, since command-lines, being mere lines of text, are easy to specify in code. CLIs are made possible by command-line interpreters or command-line processors , which are programs that read command-lines and carry out

5829-496: The most appropriate image resolution for a given printer-resolution can pose difficulties, since printed output may have a greater level of detail than a viewer can discern on a monitor. Typically, a resolution of 150 to 300 PPI works well for 4-color process ( CMYK ) printing. However, for printing technologies that perform color mixing through dithering ( halftone ) rather than through overprinting (virtually all home/office inkjet and laser printers), printer DPI and image PPI have

5916-457: The newer C:\> style, unless used on floppy drives A: or B:; on those systems PROMPT $ N$ G can be used to override the automatic default and explicitly switch to the older style. Many Unix systems feature the $ PS1 variable (Prompt String 1), although other variables also may affect the prompt (depending on the shell used). In the Bash shell, a prompt of the form: could be set by issuing

6003-506: The operating system. A program that implements such a text interface is often called a command-line interpreter, command processor or shell . Examples of command-line interpreters include Nushell , DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11 , the various Unix shells ( sh , ksh , csh , tcsh , zsh , Bash , etc.), CP/M 's CCP , DOS ' COMMAND.COM , as well as the OS/2 and

6090-422: The options easier to access. Automation of repetitive tasks is simplified by line editing and history mechanisms for storing frequently used sequences; this may extend to a scripting language that can take parameters and variable options. A command-line history can be kept, allowing review or repetition of commands. A command-line system may require paper or online manuals for the user's reference, although often

6177-474: The original pixel values can be perfectly regenerated from the compressed data. Other algorithms, such as JPEG, are lossy , because the parameterized patterns are only an approximation of the original pixel values, so the latter can only be estimated from the compressed data. Vector images (line work) can be rasterized (converted into pixels), and raster images vectorized (raster images converted into vector graphics), by software. In both cases some information

6264-464: The path of the current working directory and the hostname . On many Unix and derivative systems , the prompt commonly ends in $ or % if the user is a normal user, but in # if the user is a superuser ("root" in Unix terminology). End-users can often modify prompts. Depending on the environment, they may include colors, special characters, and other elements (like variables and functions for

6351-428: The prompt. Some CLIs, such as those in network routers , have a hierarchy of modes , with a different set of commands supported in each mode. The set of commands are grouped by association with security, system, interface, etc. In these systems the user might traverse through a series of sub-modes. For example, if the CLI had two modes called interface and system , the user might use the command interface to enter

6438-538: The prompt. In DOS' COMMAND.COM and in Windows NT's cmd.exe users can modify the prompt by issuing a PROMPT command or by directly changing the value of the corresponding %PROMPT% environment variable . The default of most modern systems, the C:\>; style is obtained, for instance, with PROMPT $ P$ G . The default of older DOS systems, C> is obtained by just PROMPT , although on some systems this produces

6525-514: The quality of the WebP-encoded result was the worst of the three, mostly because of blurriness on the image. Her main remark was that "libvpx, a much more powerful encoder than ffmpeg's jpeg encoder, loses because it tries too hard to optimize for PSNR " (peak signal-to-noise ratio), arguing instead that "good psycho-visual optimizations are more important than anything else for compression". In October 2013, Josh Aas from Mozilla Research published

6612-409: The quality of the device rendering them. Raster graphics deal more practically than vector graphics with photographs and photo-realistic images, while vector graphics often serve better for typesetting or for graphic design . Modern computer-monitors typically display about 72 to 130 pixels per inch (PPI), and some modern consumer printers can resolve 2400 dots per inch (DPI) or more; determining

6699-479: The raster data model is the tessellation of a plane, into a two-dimensional array of squares, each called a cell or pixel (from "picture element"). In digital photography , the plane is the visual field as projected onto the image sensor ; in computer art , the plane is a virtual canvas; in geographic information systems , the plane is a projection of the Earth's surface. The size of each square pixel, known as

6786-458: The same commands from other command lines (such as the BBC BASIC command line), by preceding the command with a * . A command-line argument or parameter is an item of information provided to a program when it is started. A program can have many command-line arguments that identify sources or destinations of information, or that alter the operation of the program. When a command processor

6873-423: The two-dimensional grid, the file must include a header section at the beginning that contains at least the number of columns, and the pixel datatype (especially the number of bits or bytes per value) so the reader knows where each value ends to start reading the next one. Headers may also include the number of rows, georeferencing parameters for geographic data, or other metadata tags, such as those specified in

6960-451: The user terminated by the Enter key , then execute the specified command and provide textual display of results or error messages. Advanced CLIs will validate, interpret and parameter-expand the command line before executing the specified command, and optionally capture or redirect its output. Unlike a button or menu item in a GUI, a command line is typically self-documenting, stating exactly what

7047-410: The user wants done. In addition, command lines usually include many defaults that can be changed to customize the results. Useful command lines can be saved by assigning a character string or alias to represent the full command, or several commands can be grouped to perform a more complex sequence – for instance, compile the program, install it, and run it — creating a single entity, called

7134-605: The user-interface, including fully graphically oriented ones. For example, the default Windows GUI is a shell program named EXPLORER.EXE , as defined in the SHELL=EXPLORER.EXE line in the WIN.INI configuration file. These programs are shells, but not CLIs. Application programs (as opposed to operating systems) may also have command-line interfaces. An application program may support none, any, or all of these three major types of command-line interface mechanisms: Some applications support

7221-462: Was abandoned at the Supreme Court in 1977 over the issue of the patentability of computer software. During the 1970s and 1980s, pen plotters , using Vector graphics , were common for creating precise drawings, especially on large format paper. However, since then almost all printers create the printed image as a raster grid, including both laser and inkjet printers. When the source information

7308-489: Was an actively exploited vulnerability with a high risk rating of CVSS 8.8. This could lead to an out of bounds/overflow condition in applications using the affected libwebp library, upon exploitation of a maliciously crafted .webp lossless file. This could result in a denial of service (DoS), or worse, enabling malicious remote code execution (RCE). The extensive use of libwebp packages across hundreds of applications, including all categories from web browsers to mobile apps, posed

7395-599: Was initially considered for implementation in 2013. Pale Moon implemented initial support for WebP in 2016 with its version 26 milestone. SeaMonkey began supporting WebP with its version 2.53.5 released in November 2020. GNOME Web , Midori , and Falkon natively support WebP. WebP can also be displayed in all major browsers using the WebPJS JavaScript library, although support in Internet Explorer 6 and above

7482-437: Was never finalized and was removed from the spec again. Older animated GIF files can be converted to animated WebP. On 18 November 2011, Google announced a new lossless compression mode, and support for transparency ( alpha channel ) in both lossless and lossy modes; support was enabled by default in libwebp 0.2.0 (16 August 2012). According to Google's measurements in November 2011, a conversion from PNG to WebP resulted in

7569-559: Was part of the Multics time-sharing operating system . In 1964, MIT Computation Center staff member Louis Pouzin developed the RUNCOM tool for executing command scripts while allowing argument substitution. Pouzin coined the term shell to describe the technique of using commands like a programming language, and wrote a paper about how to implement the idea in the Multics operating system. Pouzin returned to his native France in 1965, and

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