Minimize Alpha Blending In Iphone

Similar to the nested transforms discussed earlier, alpha blending is also calculated in real time. When a layer has partial transparency, that transparency is recalculated for every frame of an animation. Beware of this when animating layers that have transparency, and try to minimize the calculations as much as possible. Sliding layers behind other layers that are transparent can incur a large performance penalty.

Fortunately, there is an easy way to determine which layers have alpha blending and remove it. This is especially useful on the iPhone with its limited resources. To check for alpha blending, launch your application on the iPhone with Instruments running on the desktop. In Instruments, add the Core Animation instrument in addition to any others you want to use.

When your application runs on the iPhone and you have Instruments attached to it, to turn on the Color Blended Layers, switch in the Core Animation Instrument, as shown in Figure 12-1. As soon as you enable this switch, you see an immediate effect on the iPhone. The entire iPhone screen turns either red or green. In fact, this switch can be turned on without any applications running, and you can see its effect on the home screen, as shown in Figure 12-2.

When enabled, the Color Blended Layers option colors the layers, so you can quickly identify the trouble spots in your app. Areas marked in green do not have any alpha blending, whereas areas marked in red do. The goal with this is to eliminate as much of the red as possible. For example, in the Transparent Cocoa Touch application, you can see that all the UI Label objects

Have a transparent background when you examine the code for these areas, you can see where the issue lies. Specifically, look at the –init With Frame :reuse Identifier: of the Custom Table View Cell object; this is where the trouble lies .As you can see, the UI Label objects, title Label and description Label, both have their –background Color set to [UI Color clear Color], causing an alpha blending to occur. To correct this, change that UI Color to be the same color as the background for the entire UI Table View Cell.

Author Bio: Haword Roze is a University Lecturer and Editor of Alpha Male. She loves to write on technical topics like Personal Loan . She is writing from last three years