1

我想通过按下按钮来旋转 UIImageView。我正在使用这段代码：

#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;

在 .m 中：

- (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，我不明白为什么。有任何想法吗？

4

3 回答 3

2

这是一个猜测，这是否只发生在 Retina 屏幕上？每当从图形上下文中保存 UIImage 时，您需要确保比例正确。这就是我的做法：

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];
于 2012-12-19T22:46:50.343 回答
0

使用 Kekoa 的代码片段（非常感谢），我能够获得一个可以在基于 Apples rotateImage 代码的视网膜设备上运行的 rotateImage 函数：

- (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;
}
于 2015-03-17T15:54:41.240 回答
0

没有必要UIGraphicsGetImageFromCurrentImageContext。它是一种获取主屏幕所需部分的屏幕截图的方法。所以结果图像质量受到影响。获得旋转图像的唯一方法是......

首先旋转你的图像视图（如果你想显示旋转视图）

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

它会旋转你的图像视图。现在你将通过这些线来拍摄这个旋转的图像。（你也可以在不旋转 imgaeview 的情况下调用这些线。）

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

无需保存或截取屏幕截图或损害质量差的图像。只是享受编码。

于 2015-07-08T07:40:11.943 回答