调整图片大小问题，iphone

Question

我有我的笔尖，并根据和其一二的UIImageViews根据UISlider 代码的值调整为： -

-(IBAction)sliderChanged:(UISlider*)slider{ 
    CGFloat scaleFactor=slider.value; 

    markerImage.transform = CGAffineTransformMakeScale(scaleFactor,scaleFactor); 
} 

它被正确调整，但是当我合并这些图像一起由这些代码

UIImage *backImage=backgroundImage.image; 
UIImage *markImage=markerImage.image; 

UIGraphicsBeginImageContext(backImage.size); 

[backImage drawAtPoint:CGPointMake(0,0)]; 
[markImage drawAtPoint:CGPointMake(0,0)]; 

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

我得到了合并的图像与原始大小， 也就是说在同一维度标记图像显示的合成图像 在我怎样才能在正确的比例绘制标记图像 谢谢

Answer 1

而不是drawAtPoint:，使用drawInRect:(CGRect)rect。另外，需要使用滑块值。

0和1之间假设sliderValue，

CGRect rect = CGRectMake(0,0, markerImage.size.width*sliderValue, markerImage.size.height*sliderValue); 
[markImage drawInRect:rect]; 

编辑

CGFloat width = markerImage.size.width*sliderValue; 
CGFloat height = markerImage.size.height*sliderValue; 

CGRect rect = CGRectMake((markerImage.size.width-width)/2,(markerImage.size.height-height)/2, width, height); 
[markImage drawInRect:rect];