如何创建CGImageRefs的可变数组？ [英] How do I create a mutable array of CGImageRefs?

问题描述

我想保持CGImageRefs的可变集合。我是否需要包装他们的NSValue，如果让我怎么包装并妥善解开呢？我可以逃脱使用C数组吗？如果让我怎么构建它，我怎么后来添加的元素呢？难道是显著更昂贵的使用UIImages，而不是CGImageRefs作为集合中的元素？

I want to keep a mutable collection of CGImageRefs. Do I need to wrap them in NSValue, and if so how do I wrap and unwrap them properly? Can I get away with using a C array? If so how do I construct it and how do I add elements to it later? Is it significantly more costly to use UIImages instead of CGImageRefs as the elements of the collection?

推荐答案

通过获取CGImageRef出一个UIImage的中的 image.CGImage 的可能是昂贵的。从文档：

Getting the CGImageRef out of an UIImage via image.CGImage can be costly. From the documentation:

如果图像数据已被清除，由于内存限制，调用此方法势力数据加载回内存。重新加载图像数据可能会导致性能下降。

If the image data has been purged because of memory constraints, invoking this method forces that data to be loaded back into memory. Reloading the image data may incur a performance penalty.

如果你觉得舒服混合C ++和Objective-C，你可以使用的的std ::矢量的用于存储CGImageRef。从.M重命名你的源文件.mm和尝试这个办法：

If you feel comfortable with mixing C++ and Objective-C, you can use a std::vector for storing the CGImageRef. Rename your source file from .m to .mm and try this:

#include <vector>
...
CGImageRef i;
...
std::vector<CGImageRef> images;
images.push_back(i);

如果你想保留的向量作为一个Objective-C类的一员，你应该将它分配在堆中，没有堆栈：

If you want to keep the vector as a member of a Objective-C class, you should allocate it on the heap, not the stack:

头文件：

#include <vector>
using std;

@interface YourInterface : ...
{
   vector<CGImageRef> *images;
}

和在实现文件：

images = new std::vector<CGImageRef>();
images->push_back(i);
...
//When you're done
delete images;
images = NULL;

这篇关于如何创建CGImageRefs的可变数组？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！