Adobe 38039481 User Guide - Page 502

FLASH CS3 496 User Guide 3 Right-click (Windows) or Control-click (Macintosh) the bitmap icon in the Library window, and select Properties from the context menu to open the Bitmap Properties dialog box. 4 In the Compression pop-up menu, select one of the following options: • Select the Photo (JPEG) option for images with complex color or tonal variations, such as photographs or images with gradient fills. This option produces a JPEG file. Select the Use Imported JPEG Data check box to use the default compression quality specified for the imported image. To specify a new quality compression setting, deselect Use Imported JPEG Data and enter a value between 1 and 100 in the Quality text box. A higher setting produces an image of higher image, but also a larger file, so adjust the value accordingly. • Select the Lossless (PNG/GIF) option for images with simple shapes and a few colors. This option compresses the image using lossless compression, which discards no data. 5 Click Test to determine the results of the file compression. Compare the original file size to the compressed file size to decide whether the selected compression setting is acceptable. Set compression for all bitmap images 1 Select File > Publish Settings, and then click the Flash tab to display compression options. 2 Adjust the JPEG quality slider, or enter a value. A higher JPEG quality value produces an image of higher image quality but a larger SWF file. A lower image quality produces a smaller SWF file. Try different settings to determine the best trade-off between size and quality. Optimizing Flash Lite frames for mobile devices • Most devices that support Flash Lite play back content at about 15 to 20 frames per second (fps). The frame rate can be as low as 6 fps. During development, set the document frame rate to approximate the playback speed of the target device. This shows how the content will run on a device with limited performance. Before publishing a final SWF file, set the document frame rate to at least 20 fps or higher to avoid limiting performance in case the device supports a higher frame rate. • When using gotoAndPlay, remember that every frame between the current frame and the requested frame needs to be initialized before Flash plays the requested frame. If many of these frames contain different content, it could be more efficient to use different movie clips rather than using the Timeline. • Although preloading all content by putting it at the beginning of the file makes sense on the desktop, preloading on a mobile device can delay file startup. Space content throughout the file so that movie clips are initialized as they are used. Optimizing ActionScript for Flash Lite content on mobile devices Because of the processing speed and memory limitations on most mobile devices, follow these guidelines when developing ActionScript for Flash Lite content used on mobile devices: • Keep the file and its code as simple as possible. Remove unused movie clips, delete unnecessary frame and code loops, and avoid too many frames or extraneous frames. • Using FOR loops can be expensive because of the overhead incurred while the condition is checked with each iteration. When the costs of the iteration and the loop overhead are comparable, execute multiple operations individually instead of using a loop. The code may be longer, but performance will improve. • Stop frame-based looping as soon as it is no longer needed. • When possible, avoid string and array processing because it can be CPU-intensive.