Pixel Doubling

Windows Mobile 6.5
4/8/2010

Internet Explorer Mobile uses pixel doubling to support high-DPI devices. Pixel doubling is used by Internet Explorer Mobile only on high-DPI devices. It is not used for Internet Explorer Mobile on low-DPI devices or for applications that host the HTML control. Bubble windows continue to use the low-DPI table.

Image rendering is for content that is measured in pixels. On a high-DPI screen, the same number of pixels produce an image approximately half the size of the low-DPI screen. To maintain the original image size, Internet Explorer Mobile employs pixel doubling. For image rendering, two pixels are used on the high-DPI device for every one that is used on the original low-DPI device.

The default rendering of a page is at a logical 96 DPI. Windows Mobile pixel measurements are multiplied by using the following formula: Screen DPI divided by 96. Items defined in other units of measurement, such as point size, em, inches, or centimeters, are scaled appropriately with no additional changes.

To use high-DPI when rendering content in Internet Explorer Mobile or in the HTML control, measurements for both images and fonts should be specified in em, inches, or centimeters. This ensures that the user has control of the font size regardless of resolution, and that the font will not be scaled by Internet Explorer Mobile.

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Internet Explorer Mobile is not affected by device-wide font settings.

The following table shows the font sizes used by Internet Explorer Mobile in Windows Mobile.

Text size specification in Windows Mobile HTML font size Defined font size for 96 DPI Defined font size for 192 DPI

Largest

Large

11

10

Larger

Medium

10

8

Medium

Small

9

6.5

Smaller

X-Small

8

6

Smallest

XX-Small

7

5

A device running Windows Mobile Standard at QVGA resolution does not implement pixel doubling because, at QVGA resolution, pixel doubling causes the original image to appear larger. Instead, a device running Windows Mobile Standard at QVGA resolution implements increased font size. Compared to a device not running at QVGA resolution, pages render with slightly smaller images and approximately the same size font.

For more information about graphics and image scaling see this Microsoft Web site.

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