Adobe 38039481 User Guide - Page 492

FLASH CS3 486 User Guide 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 _visible property to false instead of changing the _alpha level to 0 or 1 in a SWF file. Calculating the _alpha level for an instance on the Stage is processor intensive. If you disable the instance's visibility, it saves CPU cycles and memory, which can give your SWF files smoother animations. Instead of unloading and possibly reloading assets, set the _visible property to false, which is less processor-intensive. • 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 ActionScript/Animation folder to access the sample. See also "Animation frame rate and performance" on page 487 "Video conventions" on page 469