Question

我想通过按下按钮来旋转UIImageView。我正在使用此代码：

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

在“UIImage-Extensions.h”中我有：

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

和.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，但是当图像旋转时，图像也会变小，我无法理解为什么。有什么想法吗？

Answer 1

这是一个猜测，这只发生在Retina屏幕上吗？每当从图形上下文保存UIImage时，您需要确保比例正确。我就是这样做的：

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];

Answer 2

使用Kekoa的片段（非常感谢），我能够获得一个工作的rotateImage函数，该函数可以在基于Apples rotateImage代码的视网膜设备上运行：

- (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;
}

Answer 3

无需UIGraphicsGetImageFromCurrentImageContext。它是一种获取所需部分主屏幕截图的方法。所以结果图像质量受到影响。获得旋转图像的唯一方法是......

首先旋转图像视图（如果要显示旋转视图）

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

它将旋转您的imageview。现在你将通过这些线条拍摄这个旋转的图像。（你可以调用这些线条而不用旋转imgaeview。）

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

无需保存或截屏或破坏质量较差的图像。只是享受编码。

通过角度旋转UIImageView

3 个答案: