Display File Structure In Computer Graphics Pdf Download
Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. Based on the PostScript language, each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, vector graphics, raster images and other information needed to display it. PDF has its roots in "The Camelot Project" initiated by Adobe co-founder John Warnock in 1991.
Display File Structure In Computer Graphics Pdf Download
PDF files may contain a variety of content besides flat text and graphics including logical structuring elements, interactive elements such as annotations and form-fields, layers, rich media (including video content), three-dimensional objects using U3D or PRC, and various other data formats. The PDF specification also provides for encryption and digital signatures, file attachments, and metadata to enable workflows requiring these features.
Historically, the PostScript-like PDF code is generated from a source PostScript file. The graphics commands that are output by the PostScript code are collected and tokenized.[clarification needed] Any files, graphics, or fonts to which the document refers also are collected. Then, everything is compressed to a single file. Therefore, the entire PostScript world (fonts, layout, measurements) remains intact.
There are two layouts to the PDF files: non-linearized (not "optimized") and linearized ("optimized"). Non-linearized PDF files can be smaller than their linear counterparts, though they are slower to access because portions of the data required to assemble pages of the document are scattered throughout the PDF file. Linearized PDF files (also called "optimized" or "web optimized" PDF files) are constructed in a manner that enables them to be read in a Web browser plugin without waiting for the entire file to download, since all objects required for the first page to display are optimally organized at the start of the file. PDF files may be optimized using Adobe Acrobat software or QPDF.
A "tagged" PDF (see clause 14.8 in ISO 32000) includes document structure and semantics information to enable reliable text extraction and accessibility. Technically speaking, tagged PDF is a stylized use of the format that builds on the logical structure framework introduced in PDF 1.3. Tagged PDF defines a set of standard structure types and attributes that allow page content (text, graphics, and images) to be extracted and reused for other purposes.
The standard security provided by PDF consists of two different methods and two different passwords: a user password, which encrypts the file and prevents opening, and an owner password, which specifies operations that should be restricted even when the document is decrypted, which can include modifying, printing, or copying text and graphics out of the document, or adding or modifying text notes and AcroForm fields. The user password encrypts the file, while the owner password does not, instead relying on client software to respect these restrictions. An owner password can easily be removed by software, including some free online services. Thus, the use restrictions that a document author places on a PDF document are not secure, and cannot be assured once the file is distributed; this warning is displayed when applying such restrictions using Adobe Acrobat software to create or edit PDF files.
PDF was selected as the "native" metafile format for Mac OS X, replacing the PICT format of the earlier classic Mac OS. The imaging model of the Quartz graphics layer is based on the model common to Display PostScript and PDF, leading to the nickname Display PDF. The Preview application can display PDF files, as can version 2.0 and later of the Safari web browser. System-level support for PDF allows Mac OS X applications to create PDF documents automatically, provided they support the OS-standard printing architecture. The files are then exported in PDF 1.3 format according to the file header. When taking a screenshot under Mac OS X versions 10.0 through 10.3, the image was also captured as a PDF; later versions save screen captures as a PNG file, though this behavior can be set back to PDF if desired.
To view an entire image or a part of image with various attributes, we need to organize image information in a particular manner since existing structure of display file does not satisfy our requirements of viewing an image. To achieve this display, file is divided into Segments. Each segment corresponds to a component and is associated with a set of attributes and image transformation parameters like scaling, rotation. Presence of Segment allows :
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Extensions tell your computer which application created or can open the file and which icon to use for the file. For example, the docx extension tells your computer that Microsoft Word can open the file and to display a Word icon when you view it in File Explorer.
Specifies if the image is interlaced.None creates an image that displays in a web browser only afterdownloading is complete. Adam7 creates an image that displays low-resolutionversions in a browser while the full image file is downloading.Adam7 can make downloading time seem shorter and assures viewersthat downloading is in progress; however, it increases file size.
PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store gamma and chromaticity data for improved color matching on heterogeneous platforms.
The PNG specification enjoys a good level of implementation with good interoperability. At the time of this publication more than 180 image viewers could display PNG images and over 100 image editors could read and write valid PNG files. Full support of PNG is required for conforming SVG viewers; at the time of publication all eighteen SVG viewers had PNG support. HTML has no required image formats, but over 60 HTML browsers had at least basic support of PNG images.
This International Standard specifies a datastream and anassociated file format, Portable Network Graphics (PNG,pronounced "ping"), for a lossless, portable, compressedindividual computer graphics image transmitted across theInternet. Indexed-colour, greyscale, and truecolour images aresupported, with optional transparency. Sample depths range from 1to 16 bits. PNG is fully streamable with a progressive displayoption. It is robust, providing both full file integrity checkingand simple detection of common transmission errors. PNG can storegamma and chromaticity data as well as a full ICC colour profilefor accurate colour matching on heterogenous platforms. ThisStandard defines the Internet Media type "image/png". Thedatastream and associated file format have value outside of themain design goal.
For high-end applications the first method provides the mostflexibility and control. The second method enables one particularcolour space to be indicated. The third method enables the exactchromaticities of the RGB data to be specified, along with thegamma correction (the power function relating the desired displayoutput with the image samples) to be applied (see Annex C: Gamma andchromaticity). It is recommended that explicit gammainformation also be provided when either the first or secondmethod is used, for use by PNG decoders that do not support fullICC profiles or the sRGB colour space. Such PNG decoders canstill make sensible use of gamma information. PNG decoders arestrongly encouraged to use this information, plus informationabout the display system, in order to present the image to theviewer in a way that reproduces as closely as possible what the image's original authorsaw .
The transform to be applied depends on the nature of the imagesamples and their precision. If the samples represent lightintensity in floating-point or high precision integer form(perhaps from a computer graphics renderer), the encoder mayperform "gamma encoding" (applying a power function with exponentless than 1) before quantizing the data to integer values forinclusion in the PNG datastream. This results in fewer bandingartifacts at a given sample depth, or allows smaller sampleswhile retaining the same visual quality. An intensity levelexpressed as a floating-point value in the range 0 to 1 can beconverted to a datastream image sample by:
Computer graphics renderers often do not perform gammaencoding, instead making sample values directly proportional toscene light intensity. If the PNG encoder receives sample valuesthat have already been quantized into integer values, there is nopoint in doing gamma encoding on them; that would just result infurther loss of information. The encoder should just write thesample values to the PNG datastream. This does not imply that thegAMA chunkshould contain a gamma value of 1.0 because the desiredend-to-end transfer function from scene intensity to displayoutput intensity is not necessarily linear. However, the desiredgamma value is probably not far from 1.0. It may depend onwhether the scene being rendered is a daylight scene or an indoorscene, etc. 350c69d7ab