如何将CorePlot创建的图形保存为jpg文件

问题描述

我正在使用CorePlot在我的应用程序中绘制不同的图形。然后，我想将此图保存到jpg文件并发布到某个社交网站（例如Twitter）。

I am using CorePlot to draw different graphs in my application. Then, I would like to save this graph to a jpg file and publish to some social networking site (e.g., Twitter).

我做了一些文档阅读并了解到以下方法对我有用：

I did some documentation reading and understood that the following methods could be useful for me:

• CGBitmapContextCreateImage：从位图图形上下文创建CGImage作为副本（即，查看我的图表所在的位置或整个屏幕 - 我理解对了吗？）

• CGBitmapContextCreateImage: creating a CGImage as a copy from a bitmap graphics context (i.e., the view where my graph is situated or the whole screen - have I understood right?)

CGImageCreateWithImageInRect：如果需要，我可以剪掉图像的某些部分

CGImageCreateWithImageInRect: I can clip out some part of the image if needed

[UIImage imageWithCGImage]：将CGImage转换为UIImage对象

[UIImage imageWithCGImage]: converting CGImage to an UIImage object

UIImageJPEGRepresentation：转换我的UIImage反对jpg NSData对象然后我可以分享到我的社交网络

UIImageJPEGRepresentation: converting my UIImage object to a jpg NSData object which then I can share to my social network

1. 第一个问题是：我理解对了吗我必须执行的操作顺序才能完成我的任务？我会自己尝试一下，但是我遇到了一个问题导致了第二个问题：

1. The first question is: have I understood right the sequence of operations I have to carry out to accomplish my task? I would have tried it out myself, but I've got a problem which leads to the second question:

从哪里获取图形上下文信息到如果我正在使用CorePlot，则进入 CGBitmapContextCreateImage ？对不起，如果这是一个愚蠢的问题，但我不是真的在家里有图形上下文。

From where do I get the graphics context info to pass into CGBitmapContextCreateImage if I am using CorePlot? Sorry if it's a dumb question, but I am not really at home with graphics contexts.

非常感谢您提前帮助！如果我在这里得到所有这些，我保证在这里发布我的代码示例。

Thanks a lot for any help in advance! And if I get with all this somewhere I promise to post my code sample here.

好吧，多亏了Brad，这真的很容易，但正如我所承诺的，我有发布行：

Well, thanks to Brad, it was really easy, but as I promissed, I have to post the lines:

CPXYGraph *graph=[[CPXYGraph alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];

// setting up the graph
// ...

UIImage *newImage=[graph imageOfLayer];
NSData *newPNG=UIImagePNGRepresentation(newImage); // or you can use JPG or PDF

// For test purposes I write the file to the Documents directory, but you can do whatever you want with your new .png file
NSString *filePath=[NSString stringWithFormat:@"%@/graph.png", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]];

if([newPNG writeToFile:filePath atomically:YES])
    NSLog(@"Created new file successfully");

推荐答案

实际上，CPLayer基类用于所有绘图元素在Core Plot中有一个名为 -imageOfLayer 的类别方法，它返回你调用它的任何层的UIImage实例。如果您想了解如何完成此操作，请参阅框架中的 CPPlatformSpecificCategories.h 和 CPPlatformSpecificCategories.m 文件。

Actually, the CPLayer base class used for all drawing elements in Core Plot has a category method called -imageOfLayer that returns a UIImage instance of whatever layer you call it on. See the CPPlatformSpecificCategories.h and CPPlatformSpecificCategories.m files in the framework if you want to see how this is accomplished.

只需在CPGraph实例上使用 -imageOfLayer ，然后使用 UIImageJPEGRepresentation（）创建该图像的JPEG版本。然后，您可以使用常规方法上传该图像。

Simply use -imageOfLayer on your CPGraph instance and then use UIImageJPEGRepresentation() to create the JPEG version of that image. You can then upload that image using the normal means.

同样，还有一个 -dataForPDFRepresentationOfLayer 方法，它返回一个NSData实例，其中包含该层的PDF表示及其子层。

Likewise, there is a -dataForPDFRepresentationOfLayer method that returns an NSData instance containing a PDF representation of the layer and its sublayers.

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