NSImage 加载图像的一部分
需求是这样的， 我会为按钮获取一个大的 PNG 图像，这个图像将包含需要显示的 hOver、按钮单击、鼠标退出的图像， 单个 PNG 文件大小为 1024 X 28，因此每个图像的大小约为 256 X 28， 我正在谷歌搜索最好的方法，但无法弄清楚如何实现这一点，
我想到了以下方法，
NSImage *pBtnImage[MAX_BUTTON_IMAGES]
for ( i = 0; i < 4 ; i++) {
pBtnImage[i] = [[NSImage alloc]initWithData:??????];
}
我想知道我应该在 NSData 参数中给出什么，
是否可以加载单个图像并相应地剪切图像当需要时。
提前致谢
The requirement is like this,
I would get a single large PNG Images for a button, this single image will contain images for hOver, button clicked , mouse exit that need to be displayed,
Single PNG File size would be 1024 X 28, so each image have size about 256 X 28,
I am googling the best possible approach but couldn't make out how to achieve this,
I have following approach in mind,
NSImage *pBtnImage[MAX_BUTTON_IMAGES]
for ( i = 0; i < 4 ; i++) {
pBtnImage[i] = [[NSImage alloc]initWithData:??????];
}
I want to know what should i give in the NSData parameter,
Is it possible to load a Single Image and clipped image accordingly as and when it needed.
Thanks in advance
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没有 Cocoa 支持的简单方法可以从图像的数据中仅读取图像的子矩形。然而，读取整个图像并在合成时仅使用图像的选定矩形是一件简单的事情。事实是，对于所有可用的 API，您可能最好只使用标准的 +[NSImage imageNamed:] 方法来单独读取图像并让操作系统处理缓存。
您想要解决什么实际的、可测量的性能问题？是否真的存在，或者这是一种过早优化的情况？
There's no simple Cocoa-supported way to read only a sub-rectangle of the image from its data. It's a simple matter, however, to read the whole image in and only use a select rectangle of the image when compositing. Thing is, with all the available API, you might be better off just to use the standard +[NSImage imageNamed:] method to read the images in individually and let the OS handle caching.
What actual, measured performance problem are you trying to solve? Does one really exist, or is this a case of premature optimization?