iPhone - 获取指向 CGDataProvider 背后的数据的指针？

发布于 2024-08-30 09:53:56 字数 513 浏览 9 评论 0原文

我正在尝试获取 CGImage 并将其数据复制到缓冲区中以供以后处理。下面的代码是我到目前为止所拥有的，但有一点我不喜欢它 - 它复制图像数据两次。一次用于 CGDataProviderCopyData()，一次用于对 imgData 的 :getBytes:length 调用。我无法找到一种方法将图像数据直接复制到缓冲区中并删除 CGDataProviderCopyData() 步骤，但必须有一种方法......有任何指针吗？（...双关语）

NSData *imgData = (NSData *)(CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef)));

CGImageRelease(myCGImageRef);

// i've got a previously-defined pointer to an available buffer called "mybuff"
[imgData getBytes:mybuff length:[imgData length]];

原文

I'm trying to take a CGImage and copy its data into a buffer for later processing. The code below is what I have so far, but there's one thing I don't like about it - it's copying the image data twice. Once for CGDataProviderCopyData() and once for the :getBytes:length call on imgData. I haven't been able to find a way to copy the image data directly into my buffer and cut out the CGDataProviderCopyData() step, but there has to be a way...any pointers? (...pun ftw)

NSData *imgData = (NSData *)(CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef)));

CGImageRelease(myCGImageRef);

// i've got a previously-defined pointer to an available buffer called "mybuff"
[imgData getBytes:mybuff length:[imgData length]];

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一绘本一梦想 2024-09-06 09:53:56

看这个答案：
CGDataProviderCopyData() 实际上复制字节吗？或者只是指针？

看起来对 CGDataProvider 后面的缓冲区的直接访问仅限于私有 API。

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感受沵的脚步 2024-09-06 09:53:56

除非你在使用Instruments测量时发现性能问题，否则我不认为复制两次是一个大问题。您始终可以直接存储 CFDataRef imgData 而不是 mybuff。

编辑
我说的是这种代码：
在你的类接口中添加一个数组：

NSMutableArray *images;

在你的 init: 方法中：创建数组：

images = [[NSMutableArray alloc] init];

并有一个 dealloc;

-(void)dealloc{
    [images release];
}

并在保存每个图像的代码中：

CGDataRef imageDataRef = CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef)));
[images addObject: (NSData*)imageDataRef];
CGRelease(imageDataRef);

Unless you see a performance problem when you use Instruments to measure it, I don't think that copying it twice is a huge problem. You could always store the CFDataRef imgData directly instead of the mybuff.

Edit
I'm talking about this kind of code:
In your class interface add an array:

NSMutableArray *images;

In your init: method: create the array:

images = [[NSMutableArray alloc] init];

and have a dealloc;

-(void)dealloc{
    [images release];
}

and in your code that saves each image:

CGDataRef imageDataRef = CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef)));
[images addObject: (NSData*)imageDataRef];
CGRelease(imageDataRef);

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