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SYMPTOMSSlides and graphics from PowerPoint for Windows may not look as good when pasted into other Windows-based programs. For example, a gradient- filled slide may not be as clear when pasted into Microsoft Word or Microsoft Excel for Windows. Or, you may notice that a slide or graphic looks fine when pasted into Microsoft Word 2000 for Windows, but when that Word document is opened in Microsoft Word 97, it does not look as good. CAUSEThis problem occurs because of the different methods in which programs handle color palettes under Windows when running with a 256-color display driver. WORKAROUNDDepending on the desired results and capabilities of the system displaying the graphics, there are several possible workarounds. Method 1: Use an Enhanced Display Driver or CardIf your display card supports the simultaneous display of 32,000 or 16.7 million colors (16 bit or 24 bit) you can install a display driver for your card that supports either of these color modes.Method 2: Switch to 16-color ModeReducing the number of colors that Windows displays simultaneously can often make complex color images actually look better when viewed in some programs. Windows can still dither the colors for which there aren't exact matching colors available.NOTE: If the color graphics are bitmaps (such as *.BMP, *.TIF, *.PCX, and so on), this is generally not a good workaround because Windows cannot dither bitmaps. Method 3: Ignore ItIf you plan to print the document that contains the PowerPoint slide, do not worry about how it looks on the screen. How it appears on the screen does not affect the print quality.Method 4: Don't Use Gradient FillsThe most common cause of this problem is using gradient fills because many very similar colors have to be available. By eliminating gradient fills and using solid backgrounds and fills, you have a much better chance that the palette in the target application can provide all the colors that you want.MORE INFORMATIONThere are several different methods of palette management used by Windows-based programs running under a 256-color video driver. Static Palette ManagementStatic palette management is what Microsoft Word 6.0 for Windows and Microsoft Excel 97 for Windows use. They have a fixed rainbow palette that they use at all times. They do not look at the objects embedded or pasted into them to see what colors they are using. They simply assume all pictures can be displayed reasonably with the rainbow palette. This is often true for bitmaps and most generic metafiles such as clip art because their colors are usually spread across a broad spectrum. The rainbow palette is designed to have colors that are relatively close to any arbitrary color.This does not work well with gradient fills (such as PowerPoint shaded backgrounds). This is because a gradient fill needs to have many very similar colors (varying only slightly from the previous color) for it to display properly. A gradient fill from a blue color to black requires approximately 30-50 shades of blue. Because the static rainbow palette must contain a mix of all colors and is limited to 256 colors total, it cannot have 30-50 shades of blue. Therefore, each of the 30-50 shades of blue map to one of the 6-12 nearest shades of blue that are available in the rainbow palette. What would have been many color bands shrinks down to a half dozen or so. Dynamic Palette ManagementDynamic palette management is the process of taking into account the color content of all objects native or foreign to your program and creating a palette that best suits that combination of objects. This is the method PowerPoint employs. To do this, the program must scan the objects that are pasted or embedded for colors.Because the combination of many objects may have more colors than can fit in the palette, there are many algorithms for choosing the best colors to omit from the palette. These colors map to other colors in the palette. This allows pictures with many similar colors (such as gradient fills) to get a better rendering. PowerPoint uses this method of palette management. It is more complex than static palette management. Applications that are not graphically driven may not employ this technique. No Palette ManagementThe final method is to have no palette management at all. This causes your program to behave as it would on a 16-color VGA system. It allows for 16 system-defined pure colors with every other color used being dithered. This is what Word version 2.0 for Windows does.One thing to note about PowerPoint pictures is that PowerPoint actually includes a palette that matches the picture in its exported pictures. For this reason, a PowerPoint slide embedded or pasted in Word 2.0 looks quite good. This is because the picture itself would tell the system what colors to put in the palette when the picture is displayed. However, multiple pictures on one page could cause degradation between each other because there is no code to manage the different pictures' palettes. Word 6.0 and Microsoft Excel 5.0 now override these palettes with their own palette management, and thus the pictures themselves have no control of the system palette. Microsoft applications that implement static palette management include:
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Last Reviewed: December 20, 1999 © 2000 Microsoft Corporation. All rights reserved. Terms of Use. |