Improve the Display Speed of Raster Images (Concept)

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Improve the Display Speed of Raster Images

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Concept

Procedure

Quick Reference

To increase the display speed of images, you can change image display quality, hide images not currently needed, use image tiling, or suppress image selection highlighting.

To increase the display speed of images, you can change image display quality from the default high quality to draft quality. Draft-quality images appear more grainy (depending on the image file type), but they are displayed more quickly than high-quality images.

You can improve the image quality when using True Color (24 or 32 bits per pixel) for raster images by selecting or clearing certain options on the Display tab in the Options dialog box. When images are displayed at optimum quality, regeneration time increases significantly. To improve performance, decrease the number of colors for the system display setting while working in a drawing.

You can increase redrawing speed by hiding images you do not need in the current drawing session. Hidden images are not displayed or plotted; only the drawing boundary is displayed. You can choose to hide an image regardless of the user coordinate system (UCS) in the current viewport.

Use Tiled Images

Tiled images are small portions (a series of tiles) of large images that load much faster than non-tiled images. If you edit or change any properties of an image, only the modified portion is regenerated, thus improving the regeneration time. TIFF (Tagged Image File Format) is the only tiled format that the program supports. The TIFF reader supports all image types:

Bitonal (1 bit per pixel)
Gray scale and indexed color (8 bits per pixel)
True Color (24 or 32 bits per pixel)

You can save tiled TIFF images with most image scanning tools. The image tiles should be no smaller than 64 x 64 pixels and no larger than 512 x 512 pixels. Additional file readers that support other tiled formats, such as CALS Type II, are available from third-party developers.

Suppress Highlighting When Selecting Images

You can turn on or off the highlighting that identifies the selection of a raster image or the image frame by selecting Highlight Raster Image Frame Only on the Display tab in the Options dialog box. You can also set theIMAGEHLT system variable directly. By default, IMAGEHLT is set to 0, to highlight only the raster image frame. Turning off highlighting of the entire image improves performance.