You are probably asking yourself, "Why should I care about graphics file formats?" Well, the average end-user (non-programmers) is only concerned with the storage of their graphics information by using a format that majority of graphics applications and filters can read. End-users are not normally concerned with the internal composition of the data within the graphics file itself. Graphic file formats can be divided into two general classes: vector and bitmap. Vector files contain data described as mathematical equations and are typically used to store line art and CAD information.
There are two major drawbacks to using vector files. One drawback is that vector files are not suitable for reproducing paintings or photographs. The second disadvantage is that complex images take a long time to display because on most display systems, each vector image has to be converted to a pixel image by a process called "rasterizing" (Cohen and Williams p. 109). The advantages of using vector images include easy editing to the image, the amount of memory used to store the image, and the display independence. On the other hand bitmap file formats (also called raster files) contain graphics information known as pixels, such as photographic images.
Pixels are the "pictures element", (Cohen and Williams p. 89) or dots on the monitor screen. There are two disadvantages to using bitmap formats. First, it requires a large amount of data to store each image. Second, bitmap images are size dependent and are not suitable for extensive editing. Changing the size of bitmap images can create major problems. Reducing them requires throwing away information; enlarging them produces blocking effects.
The major advantages of using a bitmap formats includes good image quality and the quick display speed. There are hundreds of different graphic file formats, many are similar to each other but are made to only interact with a certain computer application. Other file formats are universal and are able to correlate with many different applications or even all of them. Some file formats can be compressed so the image stored does not use a lot of memory; others are only concerned with the quality of the picture. No one, file format is defined as the best in the majority of computer graphic applications. Graphic file formats are responsible for performing various tasks such as acting as "translation devices", (Cohen and Williams p. 105) printing, and web graphics.
Each format contributes different qualities to performing these tasks. "Translation devices" (Cohen and Williams p. 105) are file formats, which are able to store and transfer an image to another computer or another program or become downloaded from the web. The goal of the transfer devices is to transfer these images without losing any of the image data and performing the transfers as quickly as possible. Some file formats were created so files can be easily transferred between Windows and Macintosh computers.
Examples of file formats that are "translation devices" (Cohen and Williams p. 105) are WMF, PDF, TIFF and GIF. The WMF file format or "Windows Metafile" (Cohen and Williams p. 113) is vector format, which was developed mainly for the use of Windows, but has been enhanced to be used in many other computer applications as well. This format also can be imported into Macintosh as well. A PDF or "Portable Document Format" (Cohen and Williams p. 115) has several advantages to it use. These advantages include its compatibility with any computer and the compression of the format allows it to be sent over Internet with ease. A TIFF or "Tagged Image File Format", (Cohen and Williams p. 108) is the best format to use to transfer an image between Windows and Macintosh computers (Cohen and Williams p. 108).
A GIF or "Graphical Interface Format" (Miano p. 171) is another compressed format that has the ability to be displayed on any computer. Each of these file formats has their share of drawbacks as well. When exported from its original program the WMF image can change colors, patterns and shapes. The PDF format is fairly new so it is often is not available unless the program used is up to date. A TIFF file format is only useful if you intend print the image that is transferred.
On the other hand a GIF format is only useful to transfer images if its intended use is for the web. The idea behind graphic file formats produced for printing is to be capable of handling right the resolution for graphics so the graphic can print smoothly. Some formats handle high-resolution, which is more suitable for commercial printing. Others were developed strictly for the lower resolution printing of office printers. There are hundreds of formats specified for the use of printing as well.
The most popular formats of choose would be TIFF formats and EPS formats. Other popular formats are DCS, PICT and PS. The majority of file formats can be used to print an image, however choosing the wrong format can result in distorted and blurry pictures. The reason a TIFF format is one of the most popular formats to use is because it is a raster format that is extremely flexible. This format is capable of handling any resolution as well as any bit depth. An EPS or "Encapsulated PostScript" (Cohen and Williams p. 110) is vector format, but can be "raster ized" (Cohen and Williams p. 109).
This format allows the images to be edited with ease and prints the image based on the resolution of the printer. A DCS or "Desktop Color Separation" (Cohen and Williams p. 111) is a variation of an EPS. It stores images in five different parts. One part is for previewing and the other parts contain printing information.
The PICT file format (PICT is short for "picture") was created by Apple for images on the first Macintosh systems. This format can be either vector or bitmap. PICT formats are useful when printing to non-PostScript printers, or ink-jet printers. A PS or "PostScript" (Cohen and Williams p. 116) is based on the same principles of an EPS except that EPS formats was created to be "embedded" ("wotsit" internet) in another file. Another difference is that a PS format can hold up to a whole book's worth of information while an EPS on the other hand cannot be more than one page. There are disadvantages to these formats as well.
For the TIFF format it is that amount editing is limited because the format is bitmap. For the EPS format as stated above the amount information stored is limited and also when placed certain programs a gray rectangle will appear in place of the graphic. A PICT format is relatively old and often creates problems when an attempt is made to print on non-PostScript printers and high-resolution image setters. The PS format also has the problem with gray rectangles appearing when viewed in certain programs. Web graphics are made to transfer information through phone lines as quickly as possible and use the information to display images on the computer screen. Web file formats used for this reason are formats, which are made to display lower resolution, usually 72 ppi (pixels per inch) and are smaller files.
There is a large variety web graphic file formats. Two of the most popular Internet file formats are GIF and JPEG. Other less commonly used formats include Windows BMP, XBM, and PNG. The majority of the Internet today relies on these formats. Other web file formats are mainly used by only one corresponding web browser or are outdated.
The GIF format is a bitmap format developed by CompuServe to compress graphics so they were very small and could be used to transfer images through the telephone line quickly. Other advantages the GIF file format provides are the ability to store multiple images per file, which allows animations to be saved in this format and it can use up to 256 colors using one to eight bits (a bit is the smallest unit of information that a computer understands) per pixel. The JPEG file format, or "Joint Photographic Experts Group" (Miano p. 35) provides the greatest compression of any bitmap format in common use (Miano p. 35). This is why the JPEG format is the most commonly used Internet file format. The Window BMP format supplies good image quality and is one of the simplest formats because it is easy to implement, easy to debug and can viewed without special tools. However, the XBM file format is considered the overall simplest format (Miano p. 31), even over the Windows BMP.
All major web browsers support this file format. PNG or "Portable Network Graphics" (Miano p. 189) is a fairly new graphic format. With the use of a lossless compression this format supports up to forty-eight bits per pixel in the color images and contains sophisticated color matching. The PNG is becoming an alternative format to use in the place of GIF, because the use of the GIF format is patented. Because the GIF format is patented its use is limited to only those who wish to go through the legal process to do so. These legal problems have caused for development of the GIF format to end.
This coupled with inherent limitations compared to other formats it causing this format to be replaced. The disadvantage of the JPEG format is that because this format uses a lossy compression a certain amount of data is thrown away when images are saved on this format. Also, since compression is applied to JPEG to make the images smaller in data size the image quality may be lower. A significant drawback to the use of the Windows BMP format is that the data size of each image is considerably big, making the format impractical to use as a web graphic. Even though the XBM format is considered the simplest its use is still limited outside Windows. The major disadvantage of the PNG format is that because it is fairly new it requires newer browsers and plug-ins to view its images.
In the long run each computer graphic task have at least two file formats, which will provide the best overall results depending on what the project is. For "translation devices" (Cohen and Williams p. 105) a TIFF format is the best format to use if the user wishes to transfer an image between Windows and Macintosh computers. However, a PDF format is the best format to use for any other kind of transfer done. For printing images the EPS format is the most suitable for printing on PostScript printers. If the user wishes to print on a non-PostScript printer then TIFF format is the file format of choice.
For web graphics a JPEG format is the best to use for photographic images, and the GIF format, soon to be replaced by PNG formats, is best for line-art images, such as icons. There are several other types graphic formats, which were not covered. Some of these files would include metafile, PDL, VRML, and multimedia formats. Metafile are formats that may contain either raster or vector graphics data.
Page Description Languages (PDL) is used to describe the layout of a printed page of graphics and text. Animation formats are usually collections of raster data that is displayed in a sequence. Multi-dimensional object formats store graphics data as a collection of objects (data and the code that manipulates it) that may be rendered (displayed) in a variety of perspectives. Virtual Reality Modeling Language (VRML) is a 3 D, object-oriented language used for describing "virtual worlds" ("wotsit" Internet) networked via the Internet and hyperlinked within the World Wide Web. Multimedia file formats are capable of storing any of the previously mentioned types of data, including sound and video information In conclusion due to the lack of information on file formats available there is a limit to the number of formats discussed. However it is evident by what was discussed that there is no one file format defined as the best in the majority of computer graphic applications.
The evidence that each computer graphic task had multiple formats, which could be characterized as the best for the task, supported this. These file formats are constantly being enhanced to take on more duties, so one day there may be one universal format developed, but until then it is best that you use these file formats for their intended uses. Work Cited Cohen, Sandee, and Williams, Robin, "The Non-Designer's Scan and Print Book" Peachpit Press; Berkeley, California, 2000. Miano, John, "Compressed Image File Formats" ACM Press; New York, New York, 1999. NC State University. "Definition of Graphic File Format Terms" NC State University Computer Services.
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Available: http: // web November 15, 2000. Robert, Debbie. "Espresso Graphics" Graphic File Format Overview. Online. Available: web UDI Lata rre. "A Manual to Graphic File Formats" Graphic File Formats.
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