通过选择另一个UIImage的一部分进行UIImage [英] UIImage by selecting part of another UIImage

问题描述

我有一个UIImage和一个CGPoint告诉我我应该将它移动到什么方向来创建另一个图像。背景可以是任何东西。

给出最初的UIImage如何创建新的UIImage？最有效的方法是什么？

这是我正在做的事情：

  int originalWidth = image.size.width; 
 int originalHeight = image.size.height; 
 float xDifference = [[coords objectAtIndex：0] floatValue]; 
 float yDifference = [[coords objectAtIndex：1] floatValue]; 
 
 
 UIView * tempView = [[UIView alloc] initWithFrame：CGRectMake（0,240，originalWidth，originalHeight）]; 
 
 UIImageView * imageView = [[UIImageView alloc] initWithImage：image]; 
 imageView.contentMode = UIViewContentModeTopLeft; 
 
 CGRect imageFrame = imageView.frame; 
 imageFrame.origin.x = xDifference; 
 imageFrame.origin.y = -yDifference; 
 imageView.frame = imageFrame; 
 
 UIGraphicsBeginImageContext（tempView.bounds.size）; 
 [tempView.layer renderInContext：UIGraphicsGetCurrentContext（）]; 
 UIImage * finalImage = UIGraphicsGetImageFromCurrentImageContext（）; 
 UIGraphicsEndImageContext（）; 
  

是否有更优的版本？

解决方案

您可以使用 很好地介绍了如何使用这个属性。

I have an UIImage and a CGPoint which tells me in what direction I should move it to create another image. The background can be anything.

Give the initial UIImage how I can create the new one? What is the most efficient way of doing it?

Here is what I'm doing:

int originalWidth = image.size.width;
int originalHeight = image.size.height;
float xDifference = [[coords objectAtIndex:0] floatValue];
float yDifference = [[coords objectAtIndex:1] floatValue];  


UIView *tempView = [[UIView alloc] initWithFrame:CGRectMake(0, 240, originalWidth, originalHeight)];

UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
imageView.contentMode = UIViewContentModeTopLeft;

CGRect imageFrame = imageView.frame;
imageFrame.origin.x = xDifference;
imageFrame.origin.y = -yDifference;
imageView.frame = imageFrame;

UIGraphicsBeginImageContext(tempView.bounds.size);
[tempView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Is there a more optimal version?

解决方案

You can use CGImageCreateWithImageInRect(). You can get a CGImage from a UIImage with the property of the same name.

Basically what you end up doing is apply masks to the existing image to extract the portions you need. Like so -

myImageArea = CGRectMake(xOrigin, yOrigin, myWidth, myHeight);//newImage
mySubimage  = CGImageCreateWithImageInRect(oldImage, myImageArea);
myRect      = CGRectMake(0, 0, myWidth*2, myHeight*2);
CGContextDrawImage(context, myRect, mySubimage);

This post gives a good idea of how to use this property.

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