Microsoft recommends a resolution of 72 pixels per inch, because most monitors have between 60 pixels and 80 pixels per inch. Saving at a higher resolution does not result in a higher-quality display, because your monitor cannot display more pixels than physically exist in the monitor. You should calculate the points per inch according to the completed size of your picture, not the original size. For example, if you are scanning an 8.5-by-2-inch letterhead for use on a Web page with a completed width of 2 inches, you can scan at 72 ppi for 2 inches, for a total of 144 pixels. The resulting file looks great when it is sized to 2 inches and is displayed on a monitor.
* หมายเหตุAt 256 colors, JPEG files offer a higher level of compression than GIF files do. However, JPEG compression does not compress some simple files as effectively as GIF compression does.
If your picture is grayscale, has large areas of one solid color, or has areas of high contrast (sharp differences between light areas and dark areas), choose the GIF format.
If your picture is in color and contains several different colors (hues) that are similar in lightness or darkness (value), choose the JPEG format, because JPEG offers better compression. JPEG compression works according to hue and works well with different hues of a similar value. JPEG compression does not work as well with similar hues at different values.
How to create good printed output is a complex subject, because of the vast number of printers that are available and the capability of each printer to produce color output and grayscale output. The primary factor for good printed output is the number of lines per inch (LPI) that your printer is capable of printing.
To print in color or grayscale, a printer must print in halftones. Halftones are arrays of dots that are arranged in a grid and that represent each image pixel as a shade of gray. For a dark gray, most of the dots in the grid are filled in. For a light gray, only a few dots on the grid are filled in. The LPI setting for the printer determines the size of this grid. 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 dot is set at a different angle from the other dots and is slightly offset, so that the dots 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 to choose the optimum resolution for scanning, in dots per inch (dpi).
To calculate your target scanning resolution, you can multiply the LPI of your printer by two. This is a general rule. To find out the LPI of your printer, see your printer documentation.
หมายเหตุ:You must experiment when you apply the general rule of multiplying the LPI by two. 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 can cause a program to stop responding or can cause Windows to stop responding.
The only exception to this rule is pure black-and-white images, or "line art" images. These images use 1 bit to store color information. Scan these images at a 1-to-1 ratio. If you have a 600 dpi printer, scan these images at 600 ppi in Line Art mode.
ขนาดแฟ้ม: ขนาดแฟ้มกำลัง ultimate จำกัดตัวเมื่อคุณทำงานกับแฟ้มของรูปภาพ ขนาดของแฟ้มเป็นสาเหตุของปัญหาทั่วไปมากที่สุดเมื่อคุณทำงานกับรูปภาพใน Microsoft Office File size is determined by the following factors: picture size, resolution, file format, compression, and color depth.
Gamma correction: This is a method to correct the lightness or darkness of pictures, so that the pictures appear with the same brightness on any monitor.
Hue: Hue describes the relative amounts of red, green, or blue in a color. For example, both pink and crimson have a red hue.
Interlaced: Interlacing is a method to send picture data over the Internet. When a picture is interlaced, the following occurs: After one sixty-fourth of the picture is downloaded, you can see a general image of what the picture looks like. As more of the picture is downloaded, the resolution improves until the whole picture is displayed.
Metafile picture: A metafile picture usually contains vector picture information. A metafile picture can contain any kind of picture data, such as a raster picture.
Palette: A palette is a list of the colors that are available to a particular picture. Different picture file formats have a different maximum number of colors. If your picture contains more colors than are available in a specific picture format, the extra colors are replaced with colors in the color palette. The colors in the resulting image may look distorted. This is known as a "paletted effect."
Pixel: A pixel is a fundamental unit of measurement in a raster-based picture or on a monitor. Both raster pictures and monitors are defined by rows of dots that can be individually assigned a color. These dots are called pixels.
Raster picture: A raster picture is a picture that is displayed by defining rows of colored dots that are placed next to each other. Each dot is assigned an individual color.
การแก้ไข: Resolution is the amount of picture data in a specific area of a picture. Resolution is usually defined in pixels per inch. The higher the resolution, the more precise and clear the picture is. However, when you increase the resolution, the file size of a picture also increases.
Transparency: Transparency is a method that allows areas of a picture to appear transparent, therefore revealing the background. There are several methods of transparency, including alpha channel transparency.
ค่า: This property describes the lightness or darkness of a color. For example, pink and baby blue have a similarค่า, although they have different hues.
Vector picture: A vector picture is made up of areas that are defined by coordinates and mathematical formulas. This file format is more versatile than a raster picture format, because vector pictures can be scaled to any size. In some cases, vector pictures can be ungrouped into smaller components.
For more information about the graphics file types that are described in this article, visit the following third-party Web sites:
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