Ios 为什么在滑块中剪切后图像模糊？

我正在使用这段代码为我的滑块为UISlider裁剪图像，当我拖动滑块时，图像正在模糊，怎么能不模糊又不丢失清晰度呢

- (UIImage *) revealedTrackImageForCurrentValues {
    //Get left and right x positions
    float lowerHandleWidth = _lowerHandleHidden ? 2.0f : _lowerHandle.frame.size.width;
    float upperHandleWidth = _upperHandleHidden ? 2.0f : _upperHandle.frame.size.width;
    float xLowerValue = ((self.bounds.size.width - lowerHandleWidth) * (_lowerValue - _minimumValue) / (_maximumValue - _minimumValue))+(lowerHandleWidth/2.0f);
    float xUpperValue = ((self.bounds.size.width - upperHandleWidth) * (_upperValue - _minimumValue) / (_maximumValue - _minimumValue))+(upperHandleWidth/2.0f);

    //Crop the image
    CGRect croppedImageRect = CGRectMake(xLowerValue, 0.0f, xUpperValue - xLowerValue, self.trackImage.size.height);
    CGImageRef croppedImageRef = CGImageCreateWithImageInRect([self.trackImage CGImage], croppedImageRect);
    UIImage *croppedImage = [UIImage imageWithCGImage:croppedImageRef];
    CGImageRelease(croppedImageRef);

    return croppedImage;

}

如何在不丢失图像清晰度的情况下执行此操作？？？

编辑的代码： 您必须将UIImage子类化：

UIImageView+裁剪.h 然后调用您的代码：

#import "UIImage+Cropping.h"

- (UIImage *)revealedTrackImageForCurrentValues 
{
    //Get left and right x positions
    float lowerHandleWidth = _lowerHandleHidden ? 2.0f : _lowerHandle.frame.size.width;
    float upperHandleWidth = _upperHandleHidden ? 2.0f : _upperHandle.frame.size.width;
    float xLowerValue = ((self.bounds.size.width - lowerHandleWidth) * (_lowerValue - _minimumValue) / (_maximumValue - _minimumValue))+(lowerHandleWidth/2.0f);
    float xUpperValue = ((self.bounds.size.width - upperHandleWidth) * (_upperValue - _minimumValue) / (_maximumValue - _minimumValue))+(upperHandleWidth/2.0f);

    // Get rect
    CGRect croppedImageRect = CGRectMake(xLowerValue, 0.0f, xUpperValue - xLowerValue, self.trackImage.size.height);

    //Get cropped image
    UIImage *croppedImage = [self.trackImage revealedTrackImageForRect: croppedImageRect];

    return croppedImage;
}

---

它给出了这一行的错误[self-drawAtPoint:CGPointMake（-cropeImage.origin.x，-cropeImage.origin.y）]；我做什么？？？@MayankPatel请检查更新的代码。它是动态编写的，但应该可以工作UIImage*croppedImage=[self.trackImage revealedTrackImageForRect:croppedImageRect]，，，它给我在这行错误没有界面界面声明我刚刚测试过，它的工作非常好，为我。我不知道你是在哪里出错的。从这里很难说，让我们来。

#import "UIImage+Cropping.h"

@implementation UIImage (Cropping)


- (UIImage *)revealedTrackImageForRect:(CGRect)croppedImageRect
{
    //create drawing context
    UIGraphicsBeginImageContextWithOptions(croppedImageRect.size, NO, 0.0f);

    //draw
    [self drawAtPoint:CGPointMake(-croppedImageRect.origin.x, -croppedImageRect.origin.y)];

    //capture resultant image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    //return image
    return image;
}

@end

#import "UIImage+Cropping.h"

- (UIImage *)revealedTrackImageForCurrentValues 
{
    //Get left and right x positions
    float lowerHandleWidth = _lowerHandleHidden ? 2.0f : _lowerHandle.frame.size.width;
    float upperHandleWidth = _upperHandleHidden ? 2.0f : _upperHandle.frame.size.width;
    float xLowerValue = ((self.bounds.size.width - lowerHandleWidth) * (_lowerValue - _minimumValue) / (_maximumValue - _minimumValue))+(lowerHandleWidth/2.0f);
    float xUpperValue = ((self.bounds.size.width - upperHandleWidth) * (_upperValue - _minimumValue) / (_maximumValue - _minimumValue))+(upperHandleWidth/2.0f);

    // Get rect
    CGRect croppedImageRect = CGRectMake(xLowerValue, 0.0f, xUpperValue - xLowerValue, self.trackImage.size.height);

    //Get cropped image
    UIImage *croppedImage = [self.trackImage revealedTrackImageForRect: croppedImageRect];

    return croppedImage;
}