Adobe 38039336 - Flash CS3 Professional User Manual page 493

Optimizing graphics and animation
Before you create optimized and streamlined animations or graphics, outline and plan your project. Make a target
for the file size and length of the animation, and test throughout the development process.
Follow these guidelines to optimize graphics and animation:
• Avoid using gradients, because they require many colors and calculations to be processed, which is more difficult
for a computer processor to render.
• For the same reason, keep the amount of alpha or transparency you use in a SWF file to a minimum.
Animating objects that include transparency is processor-intensive and should be kept to a minimum. Animating
transparent graphics over bitmaps is a particularly processor-intensive kind of animation, and must be kept to a
minimum or avoided completely.
Note: The best bitmap format to import into Flash is PNG, which is the native file format of Macromedia Fireworks from
Adobe. PNG files have RGB and alpha information for each pixel. If you import a Fireworks PNG file into Flash, you
retain some ability to edit the graphic objects in the FLA file.
• Optimize bitmaps without overcompressing them. A 72-dpi resolution is optimal for the web. Compressing a
bitmap image reduces file size, but compressing it too much compromises the quality of the graphic. Check that
the settings for JPEG quality in the Publish Settings dialog box do not overcompress the image. Representing an
image as a vector graphic is preferable in most cases. Using vector images reduces file size, because the images are
made from calculations instead of many pixels. Limit the number of colors in your image while still retaining
quality.
Note: Avoid scaling bitmaps larger than their original dimensions, because it reduces the quality of the image and is
processor intensive.
• Set the
property to
_visible
level for an instance on the Stage is processor intensive. If you disable the instance's visibility, it saves CPU
_alpha
cycles and memory, which can give your SWF files smoother animations. Instead of unloading and possibly
reloading assets, set the
• Reduce the number of lines and points you use in a SWF file. Use the Optimize Curves dialog box (Modify >
Shape > Optimize) to reduce the number of vectors in a drawing. Select the Use Multiple Passes option for more
optimization. Optimizing a graphic reduces file size, but compressing it too much compromises its quality.
However, optimizing curves reduces your file size and improves SWF file performance. Third-party options are
available for specialized optimization of curves and points that yield different results.
To get the best results, try different ways of producing animated content, and test each of the options.
A higher frame rate (measured in frames per second, or fps) produces smooth animation in a SWF file but it can be
processor-intensive, particularly on older computers. Test your animations at different frame rates to find the lowest
frame rate possible.
For a sample of scripted animation, see the Flash Samples web page at www.adobe.com/go/learn_fl_samples.
Download and decompress the Samples zip file and navigate to the ActionScript2.0/Animation folder to access the
sample.
See also
"Animation frame rate and performance" on page 488
"Video conventions" on page 470
instead of changing the
false
property to
_visible false
level to 0 or 1 in a SWF file. Calculating the
_alpha
, which is less processor-intensive.
FLASH CS3 487
User Guide