ios - CIContext如何使用drawImage :inRect:fromRect: with a CADisplayLink
<p><p> <a href="http://developer.apple.com/library/ios/DOCUMENTATION/GraphicsImaging/Reference/QuartzCoreFramework/Classes/CIContext_Class/Reference/Reference.html#//apple_ref/occ/instm/CIContext/drawImage%3ainRect%3afromRect%3a" rel="noreferrer noopener nofollow">From the docs on <code>CIContext drawImage:inRect:fromRect:</code></a> :</p>
<blockquote>
<p>.. On iOS 6, this method is asynchronous ..</p>
</blockquote>
<p>所以如果我在 <a href="http://developer.apple.com/library/ios/#documentation/QuartzCore/Reference/CADisplayLink_ClassRef/Reference/Reference.html" rel="noreferrer noopener nofollow">CADisplayLink</a> 中使用它它遇到了一个问题，因为它将继续以 60fps 的速度触发异步绘图，而实际绘图可能无法跟上。 </p>
<pre><code>- (void) displayLinkDidFire:(CADisplayLink *)displatLink;
{
CFTimeInterval duration = ;
CGFloat fps = round (1.0 / duration);
NSLog(@"%f fps", fps); // Always logs 60 fps since drawImage is async
// This method is fast since a CIImage is just a 'recipe' for an image
CIImage * result = ;
// This drawing is unable to keep up with the calls to the displayLinkDidFire method
[self.ciContext drawImage:result
inRect:self.destFrame
fromRect:self.targetFrame];
}
</code></pre>
<p>我该如何解决这个问题？</p>
<hr/>
<p><strong>编辑 - 更多信息</strong></p>
<p>我正在使用带有 <code>EAGLContext</code> 的 CoreImage(根据 WWDC 以获得更好的绘图性能)。</p>
<pre><code>self.eaglContext = [ initWithAPI:kEAGLRenderingAPIOpenGLES2];
self.ciContext = [CIContext
contextWithEAGLContext:self.eaglContext
options: @{kCIContextWorkingColorSpace:} ];
GLKView *view = (GLKView *)self.view;
view.context = self.eaglContext;
view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
NSURL * testImageURL = [ URLForResource:@"image" withExtension:@"jpg"];
NSAssert(nil != testImageURL, @"Image not found");
self.image = [CIImage imageWithContentsOfURL:testImageURL
options:@{ kCIImageColorSpace: }];
;
self.displayLink = ;
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>解决方案是使用“OpenGL ES 渲染循环”，而不是尝试使用 <code>CADisplayLink</code> 构建一个。幸运的是，这很容易，因为 <a href="http://developer.apple.com/library/ios/#documentation/GLkit/Reference/GLKViewController_ClassRef/Reference/Reference.html" rel="noreferrer noopener nofollow"><code>GLKViewController</code></a>自动执行此操作:</p>
<blockquote>
<p>The GLKViewController class provides all of the standard view controller functionality, but additionally implements an OpenGL ES rendering loop.</p>
</blockquote>
<p>唯一的缺点是这将您与使用 <code>GLKViewController</code> 紧密联系在一起，而不是仅仅将 <code>GLKView</code> 添加到现有的 UIView。要解决这个问题，您需要弄清楚如何实现自己的 OpenGL ES 渲染循环。 </p>
<pre><code>// The GLKViewController automatically calls this method
- (void) updateScreen
{
CIImage * result = ;
// Clears the screen to a grey color
glClearColor(0.5, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
[self.ciContext drawImage:result
inRect:self.destFrame
fromRect:self.targetFrame];
// `display` needs to be called here according to the docs.
GLKView *view = (GLKView *)self.view;
;
}
</code></pre></p>
<p style="font-size: 20px;">关于ios - CIContext如何使用drawImage :inRect:fromRect: with a CADisplayLink，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/17898890/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/17898890/
</a>
</p>
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