TechNote (Archived)

Bitmaps shift in Macromedia Flash

Issue

Bitmaps can appear different in the Macromedia Flash editor than in the SWF or in the browser when viewed on a machine with display set to 32-bit color. Sometimes they can also "jump" and appear to change position on the stage.

Some bitmaps shift approximately 1 pixel when Flash reaches a keyframe. This may happen as part of an alpha tween, although the screen location has not changed.
The image looks "banded" or aliased in the browser, even if the bitmap quality settings are set to "Best"

Reason

Flash occasionally exhibits odd behavior calculating the position of the bitmap on screen. This can cause the image to shift.

Solution

There are several simple solutions that will resolve this problem.

In some cases, turning off "Allow Smoothing" in the Library's Bitmap Properties dialog box will eliminate the issue.
Convert the bitmap to individual pieces using Modify > Break Apart. If the bitmap is inside a symbol, edit the symbol and break it apart there.
Resizing the image slightly often cures this problem. Use the scale tool to resize the image by a tiny amount.
If the jumping occurs during an alpha tween, try a different alpha value in either the start or finish of the tween. Instead of using 100% alpha, use 99% instead. Similarly, use 1% instead of 0%, if necessary.