以角度旋转UIImageView

  • Z时代
  • 2024-01-10
  • 分类：问答

我想通过按下按钮来旋转UIImageView。我使用此代码：以角度旋转UIImageView

#import "UIImage-Extensions.h" 
UIImage *rotatedImage = [SplashItGroupPicker.image imageRotatedByDegrees:360/arrayCount]; 
SplashItGroupPicker.image = rotatedImage;

和 “的UIImage-Extensions.h” 我有：

@interface UIImage (CS_Extensions) 
- (UIImage *)imageRotatedByRadians:(CGFloat)radians; 
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;

，并在.M：

- (UIImage *)imageRotatedByRadians:(CGFloat)radians 
{ 
return [self imageRotatedByDegrees:RadiansToDegrees(radians)]; 
} 
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees 
{ 
// calculate the size of the rotated view's containing box for our drawing space 
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width,  self.size.height)]; 
CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees)); 
rotatedViewBox.transform = t; 
CGSize rotatedSize = rotatedViewBox.frame.size; 
// Create the bitmap context 
UIGraphicsBeginImageContext(rotatedSize); 
CGContextRef bitmap = UIGraphicsGetCurrentContext(); 
// Move the origin to the middle of the image so we will rotate and scale around the center. 
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2); 
// // Rotate the image context 
CGContextRotateCTM(bitmap, DegreesToRadians(degrees)); 
// Now, draw the rotated/scaled image into the context 
CGContextScaleCTM(bitmap, 1.0, -1.0); 
CGContextDrawImage(bitmap, CGRectMake(-self.size.width/2, -self.size.height/2, self.size.width, self.size.height), [self CGImage]); 
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 
return newImage; 
}

...旋转工作正常，但当图像旋转时，图像也变小，我不明白为什么。有任何想法吗？

回答：

这是一个猜测，这是唯一发生在视网膜屏幕上吗？每当从图形上下文中保存UIImage时，都需要确保比例是正确的。这是我如何做它：

CGFloat scale = [[UIScreen mainScreen] scale]; 
CGSize size = CGSizeMake(rotatedViewBox.frame.size.width * scale, rotatedViewBox.frame.size.height * scale); 
UIGraphicsBeginImageContext(size); 
/* Do your image manipulations here */ 
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 
// overwrite the image with one that has the correct scale set 
newImage = [UIImage imageWithCGImage:newImage.CGImage scale:scale orientation:newImage.imageOrientation];

回答：

使用Kekoa的片段（感谢一吨），我是能够得到一个工作rotateImage功能，基于苹果在视网膜显示设备的工作原理rotateImage代码：

- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees { 
    CGFloat radians = DegreesToRadians(degrees); 
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, self.size.width, self.size.height)]; 
    CGAffineTransform t = CGAffineTransformMakeRotation(radians); 
    rotatedViewBox.transform = t; 
    CGSize rotatedSize = rotatedViewBox.frame.size; 
    UIGraphicsBeginImageContextWithOptions(rotatedSize, NO, [[UIScreen mainScreen] scale]); 
    CGContextRef bitmap = UIGraphicsGetCurrentContext(); 
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2); 
    CGContextRotateCTM(bitmap, radians); 
    CGContextScaleCTM(bitmap, 1.0, -1.0); 
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width/2, -self.size.height/2 , self.size.width, self.size.height), self.CGImage); 
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    return newImage; 
}

回答：

有没有必要UIGraphicsGetImageFromCurrentImageContext。它是获取屏幕所需部分屏幕截图的一种方式。所以结果图像质量受到影响。获得旋转图像的唯一方法就是...

首先由图像旋转视图（如果你想显示旋转视图）

[mainImgV setTransform:CGAffineTransformRotate(mainImgV.transform, M_PI)];

它会旋转你的ImageView。 现在你将这些行采取这种旋转图像。（你也可以调用这些线不旋转imgaeview。）

CGImageRef cgRef = mainImgV.image.CGImage; 
    newImage = [[UIImage alloc] initWithCGImage:cgRef scale:1.0 orientation:UIImageOrientationDown];

没有必要保存或采取截图或妥协质量差的形象。只是享受编码。

以上是 以角度旋转UIImageView 的全部内容， 来源链接： utcz.com/qa/259569.html

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