ios - CIContext如何使用drawImage :inRect:fromRect: with a CADisplayLink

From the docs on CIContext drawImage:inRect:fromRect: :

.. On iOS 6, this method is asynchronous ..

所以如果我在 CADisplayLink 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。

- (void) displayLinkDidFireCADisplayLink *)displatLink;
{
    CFTimeInterval duration = [displatLink 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 = [Helper generateCIImage];

    // This drawing is unable to keep up with the calls to the displayLinkDidFire method
    [self.ciContext drawImage:result
                       inRect:self.destFrame
                     fromRect:self.targetFrame];
}

我该如何解决这个问题？

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编辑 - 更多信息

我正在使用带有 EAGLContext 的 CoreImage(根据 WWDC 以获得更好的绘图性能)。

self.eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

self.ciContext = [CIContext
                  contextWithEAGLContext:self.eaglContext
                  options: @{kCIContextWorkingColorSpace:[NSNull null]} ];

GLKView *view = (GLKView *)self.view;
view.context = self.eaglContext;
view.drawableDepthFormat = GLKViewDrawableDepthFormat24;

NSURL * testImageURL = [[NSBundle mainBundle] URLForResource"image" withExtension"jpg"];
NSAssert(nil != testImageURL, @"Image not found");

self.image = [CIImage imageWithContentsOfURL:testImageURL
                                     options{ kCIImageColorSpace:[NSNull null] }];

[EAGLContext setCurrentContext:self.eaglContext];

self.displayLink = [CADisplayLink displayLinkWithTarget:self selectorselector(displayLinkDidFire];

glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);

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Best Answer-推荐答案

解决方案是使用“OpenGL ES 渲染循环”，而不是尝试使用 CADisplayLink 构建一个。幸运的是，这很容易，因为 GLKViewController自动执行此操作:

The GLKViewController class provides all of the standard view controller functionality, but additionally implements an OpenGL ES rendering loop.

唯一的缺点是这将您与使用 GLKViewController 紧密联系在一起，而不是仅仅将 GLKView 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。

// The GLKViewController automatically calls this method
- (void) updateScreen
{        
    CIImage * result = [Helper generateCoreImage];

    // 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;
    [view display];
}

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： https://stackoverflow.com/questions/17898890/