复合颜色：iPhone上的CALayer和混合模式

问题描述

我正在尝试在iphone上使用核心图像。我可以使用quartz来合成我的颜色以绘制uiview，但我想将每个组件分成 CALayer （UIview消耗更多资源）。

I'm trying to use core image on the iphone. I'm able to composite my colors using quartz to draw an uiview, but I want to separate each component into CALayer (UIview consume more resources).

所以我想用一个白色面具来过滤背景位图，我想尝试不同的混合模式。不幸的是，这些图层只是添加它们的颜色。

So I have a white mask I want to use to filter a background bitmap, and I want to try different blending mode. Unfortunately, the layers are only "adding" their colors.

这是我的代码：

@implementation WhiteLayerHelper

    - (void)drawLayer:(CALayer *)theLayer
            inContext:(CGContextRef)myContext
    {
        // draw a white overlay, with special blending and alpha values, so that the saturation can be animated
        CGContextSetBlendMode(myContext,kCGBlendModeSaturation);
        CGContextSetRGBFillColor(myContext,1.0,1.0,1.0,0.9);
        CGContextFillRect(myContext,[UIScreen mainScreen].bounds);

    }

@end

在这里是主视图 drawrect 代码，我使用我的CALayer：

And here is the main view drawrect code, where I use my CALayer:

- (void)drawRect:(CGRect)rect {
    //get the drawing context
    CGContextRef myContext = UIGraphicsGetCurrentContext();
    // draw the background
    [self fillContext:myContext withBounds:m_overlayRect withImage:m_currentImage];
    [whiteLayer renderInContext:myContext];

}

有什么问题吗？

推荐答案

我设法通过直接将它们绘制到UIView的图形上下文来获得合成多个CALayers的效果。

I managed to get the affect of compositing multiple CALayers by drawing them directly into a UIView's graphics context.

-(void)drawRect:(CGRect)rect {
 CGContextRef c = UIGraphicsGetCurrentContext();
 CGContextSetBlendMode(c, kCGBlendModeDifference);
 [myLayer drawInContext:c];
}

BTW，我没有将图层添加为视图图层的子图层（我永远不会调用[myView.layer addSublayer：myLayer]）

BTW, I did not add the layers as sublayers of the view's layer (that is I never called [myView.layer addSublayer:myLayer])

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