When images in an eBook are too big to display on the current device, the image is automatically scaled down to fit the available space on screen. This scaling invariably reduces the quality of the .jpeg, .gif, or .png image, though the degree of image degradation depends on the amount of scaling, the presence or absence of text, and the presence or absence of high-contrast lines. In particular, text in an image always suffers in comparison to text rendered with ClearType, so scaling text in an image can sometimes create a jarring mismatch with the body of the book.
To minimize the negative affects of scaled images, make sure that the images aren't scaled in the first place. To do this, use the recommended image sizes for covers, cover page images, and thumbnails, and keep interior illustrations small enough to fit within the active page area.
In particular, an 800 x 600 pixel screen can only display an interior image that is 300 pixels wide (or less) without scaling. Many laptop monitors use 800x600 pixel screens.
A 1024 x 768 pixel monitor is fairly standard for desktop monitors. A screen of this size can display an interior eBook illustration up to 400 pixels wide without scaling. Images wider than 400 pixels will scale and may suffer from a loss of image clarity.
Publishers can—and in some cases, should—ignore these limits for books that require especially crisp or especially large graphics. Many monitors are capable of displaying as much as 1152 x 864, 1280 x 1024, or even 1600 x 1200 pixels. Include warnings to readers to reset monitors when reading certain eBooks to provide better quality graphics for photo- or image-heavy eBooks.
Caution: Overlapping images can drop characters. When two images are floated, one float: right
and one float: left
, the Reader layout engine can sometimes drop letters if the two images overlap. Be sure to include a <br clear="all" />
between images.
© 2000 Microsoft Corporation. All rights reserved. Terms of use.