放大CATiledLayer时如何在未转换的上下文上绘制？ [英] How to draw on a non-transformed context while zoomed in a CATiledLayer?

问题描述

我正在使用CATiledLayer来可视化数据。默认情况下，drawLayer函数获取转置和缩放的上下文，这使绘图代码与缩放级别和所请求的图块无关。

但是，我想使用缩放功能来更改数据的水平范围，而不会发生实际的缩放。

I'm using a CATiledLayer for the visualisation of data. By default the drawLayer function gets a transposed and scaled context, which allow the drawing code to be agnostic of the zoom-level and the tile that's being requested.
However, I would like to use the zoom functionality to change the horizontal range of the data, without actual zooming occuring.

到目前为止，我得到了以下代码：

So far, I got this code:

(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context {

    /* retrieve the transformation matrix from the context. */
    CGAffineTransform contextTrans = CGContextGetCTM(context); 

    /* Scale the context back, so all items will still have the same size */
    CGContextScaleCTM(context, 1.0/contextTrans.a, 1.0/contextTrans.d); 

    <.. loop through all datapoints ..> {
        /* Transpose the point-centers to the new zoomed context */
        xCoord = xCoord * contextTrans.a;
        yCoord = yCoord * contextTrans.d;
    }
    <.. drawing code ..>
}

此方法有效，但缺点是放大时元素变得模糊。 （每个屏幕像素仅渲染1 / zoomfactor像素）。

是否有任何方法可以防止这种模糊现象发生？

或者，有什么方法可以吸引非转换的上下文，而不是转换的上下文？

This works, but has the disadvantage that the elements get blurry when zoomed in. (only 1/zoomfactor pixels are rendered for each on-screen pixel)
Any methods to prevent this blurryness from happening?
Alternatively, is there any way to draw to the non-transformed context, rather than the transposed one?

推荐答案

我认为我对这个问题的回答应该可以满足您的需求。

I think my answer to this question should do what you need.

这篇关于放大CATiledLayer时如何在未转换的上下文上绘制？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！