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Guidelines for selecting the appropriate picture format
Article ID: 272399 - View products that this article applies to.
This article was previously published under Q272399
This article discusses the following topics:
For detailed descriptions and limitations of the graphics filters that are included with Office 2000, click the article number below to view the article in the Microsoft Knowledge Base:
210396This article is divided into the following sections:
(http://support.microsoft.com/kb/210396/ )Descriptions and limitations of graphics filters included with Office 2000
Picture Formats - Raster Pictures
BMP - Windows BitmapWindows bitmaps store a single raster image in any color depth, from black and white to 24-bit color. The Windows bitmap file format is compatible with other Microsoft Windows programs. It does not support file compression and is not suitable for Web pages.
Overall, the disadvantages of this file format outweigh the advantages. For photographic quality images, a PNG, JPG, or TIF file is often more suitable. BMP files are suitable for wallpaper in Windows.
PCX - PC PaintbrushPC Paintbrush pictures, also called Z-Soft bitmaps, store a single raster image at any color depth. Paintbrush pictures are more widely used in earlier Windows and MS-DOS-based programs, and are still compatible with many newer programs. PCX pictures support internal Run Length Encoded (RLE) compression.
PNG - Portable Network GraphicPNG pictures store a single raster image at any color depth. PNG is a platform-independent format that supports a high level of lossless compression, alpha channel transparency, gamma correction, and interlacing. It is supported by more recent Web browsers.
JPG - Joint Photographic Experts Group (JPEG)JPEG pictures store a single raster image in 24-bit color. JPEG is a platform-independent format that supports the highest levels of compression; however, this compression is lossy. Progressive JPEG files support interlacing.
The level of JPEG file compression can be increased or decreased, sacrificing image quality for file size. The compression ratio can be as high as 100:1. (The JPEG format comfortably compresses files at a 10:1 to 20:1 ratio with little picture degradation.) JPEG compression works well with photo-realistic artwork. However, in simpler artwork with fewer colors, sharp levels of contrast, solid borders, or large solid areas of color, JPEG compression does not provide superior results. Sometimes the compression ratio is as low as 5:1, with a high loss of picture integrity. This happens because the JPEG compression scheme compresses similar hues well, but does not work as well with sharp differences in brightness or solid areas of color.
GIF - Graphics Interchange FormatGIF pictures store single or multiple raster image data in 8-bit, or 256 colors. GIF pictures support transparency, compression, interlacing, and multiple-image pictures (animated GIFs).
GIF transparency is not alpha channel transparency, and cannot support semi-transparent effects. GIF compression is LZW compression, at a roughly 3:1 ratio. Animated GIFs are supported in the GIF89a version of the GIF file specification.
TIFF - Tagged Image File FormatTIFF pictures store a single raster image at any color depth. TIFF is arguably the most widely supported graphic file format in the printing industry. It supports optional compression, and is not suitable for viewing in Web browsers.
The TIFF format is an extensible format, which means that a programmer can modify the original specification to add functionality or meet specific needs. This can lead to incompatibilities between different types of TIFF pictures.
Picture Formats - Vector Pictures
DXF - AutoCAD Drawing Interchange FileThe DXF format is a vector-based, ASCII format that Autodesk's AutoCAD program uses. AutoCAD provides highly detailed schematics that are completely scalable.
CGM - Computer Graphics MetafileThe CGM metafile can contain vector and bitmap information. It is an internationally standardized file format used by many organizations and government agencies, including the British Standards Institute (BSI), American National Standards Institute (ANSI), and the United States Department of Defense.
CDR - CorelDRAW!The CorelDRAW! metafile can contain both vector and bitmap information. It is a widely used, artistic design file format.
WMF - Windows MetafileThe Windows Metafile is a 16-bit metafile format that can contain both vector and bitmap information. It is optimized for the Windows operating system.
EPSF - Encapsulated PostScript FormatThe Encapsulated PostScript Format is a proprietary, printer description language that can describe both vector and bitmap information.
EMF - Enhanced MetafileThe Enhanced Metafile format is a 32-bit format that can contain both vector and bitmap information. It is an improvement over the Windows Metafile Format and contains extended features such as:
PICT - Macintosh PictureThe PICT file is a 32-bit metafile format for the Macintosh. PICT files use Run Length Encoded (RLE) internal compression, which works reasonably well. PICT files support JPEG compression if QuickTime is installed (Macintosh only).
Resolution and Color DepthThis section discusses the appropriate color depth and resolution for raster pictures. If you save pictures with the proper resolution and color settings, you create smaller files. Smaller files mean smaller, faster documents and presentations. It is in your best interest to make a picture as small as possible, given your picture usage requirements.
On Screen Display
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Note Microsoft recommends a resolution of 72 pixels per inch, because most monitors have between 60 and 80 pixels per inch. Saving at a higher resolution does not result in a higher quality display, because your monitor can't display more pixels than physically exist in the monitor. You should calculate the points per inch according to finished size, not starting size. For example, if you are scanning an 8.5-by-2-inch letterhead for use on a Web page with a finished width of 2 inches, you would scan at 72 ppi for 2 inches, for a total of 144 pixels. The resulting file looks great when sized to 2 inches and displayed on a monitor.
*Note At 256 colors, JPG files offer a higher level of compression than GIF files do. However, JPG compression does not compress some simple files as well as GIF compression does.
Printed OutputHow to create good printed output is a complex subject, because of the vast number of printers available and the capabilities of each to produce color and grayscale output. The primary factor in creating quality output is the number of lines per inch (LPI) that your printer is capable of.
To print in color or grayscale, a printer must print in halftones. Halftones are arrays of dots that are arranged in a grid and represent each image pixel as a shade of gray. For a dark gray, most of the dots in the grid are filled in, whereas for a light gray, only a few dots are filled in on the grid. The size of this grid is determined by the LPI setting for that printer. The higher the LPI, the smaller the grid, and the fewer shades of gray the printer can render.
To print in color, the printer must print overlapping lines of colored dots, each at a different angle from the other, and slightly offset so that they do not completely cover each other. This measurement is known as the Screen Frequency and is represented in degrees of rotation of the lines of dots that make up that color.
The following table helps you select the optimum scanning resolution in dots per inch (dpi).
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A good rule is to multiply the LPI for your printer by two, to calculate your target scanning resolution. To find out your printer's LPI, check your printer documentation.
Note You need to experiment when you apply this general rule. Some printers support very high resolutions. If you save your picture at more than 300 ppi, larger pictures may take up large amounts of disk space and may slow down other operations on your computer. Multiple large pictures in a document could cause a program or Windows to stop responding. For more information about how to determine the size of bitmap pictures, click the article number below to view the article in the Microsoft Knowledge Base:
132271The only exception to this rule is with pure black and white, or "line art" images. These images use 1 bit to store color information. With these images you should scan at a 1-to-1 ratio. If you have a 600 dpi printer, you should scan at 600 ppi in Line Art mode.
(http://support.microsoft.com/kb/132271/ )Importing bitmaps: Determining size and memory requirements
If you want your picture to be in grayscale or to have fewer than 256 colors, then use either the TIFF or GIF format. The TIFF format is the printing industry standard for graphics, because it does not use a lossy compression scheme, which other formats such as JPEG do. It also supports multiple levels of transparency, which few other formats do.
If the picture has more than 256 colors, save it in the TIFF or PNG format. Microsoft recommends the PNG format if you need transparency; otherwise use the TIFF format.
You should still save your picture at printer resolution for the finished picture size. For example, assume that you have an 8.5-by-2-inch letterhead, and you want to print it at a size of 2 inches. If your printer supports 600 dpi and an LPI of 85, set the picture resolution to 150 ppi at 2 inches, for a size of 300 x 71 pixels.
Note If you are saving a picture for use in Microsoft Publisher 2000, and you want to separate areas of the picture into different spot colors, click the article number below to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/264870/ )How to assign and separate spot colors in EPS graphics in Publisher 2000
For more information about the graphic file types that are described in this article, visit the following third-party Web sites:
http://www.adobe.com/devnet/postscript/Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Article ID: 272399 - Last Review: April 30, 2012 - Revision: 6.0