how to get UIView 's angle after CGAffineTransform?

最新推荐文章于 2018-05-03 16:00:20 发布

转载最新推荐文章于 2018-05-03 16:00:20 发布 · 52 阅读

本文介绍了一种使用Objective-C在iOS应用中旋转CGImage的方法。通过计算旋转角度并利用CGAffineTransform进行旋转操作，实现了对图像的精确旋转。文章详细展示了如何创建位图上下文、设置抗锯齿和插值质量等步骤。

CGFloat radians = atan2f(self.view.transform.b, self.view.transform.a);

CGFloat degrees = radians * (180 / M_PI);

NSLog(@"%f %f %f", acos (MyView.transform.a), asin (MyView.transform.b), atan2(MyView.transform.b,MyView.transform.a));

- (CGImageRef)CGImageRotatedByAngle:(CGImageRef)imgRef angle:(CGFloat)angle
{
  CGFloat angleInRadians = angle * (M_PI / 180);
  CGFloat width = CGImageGetWidth(imgRef);
  CGFloat height = CGImageGetHeight(imgRef);

  CGRect imgRect = CGRectMake(0, 0, width, height);
  CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
  CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, transform);

  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef bmContext = CGBitmapContextCreate(NULL,
                                                 rotatedRect.size.width,
                                                 rotatedRect.size.height,
8,
0,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedFirst);
  CGContextSetAllowsAntialiasing(bmContext, FALSE);
  CGContextSetInterpolationQuality(bmContext, kCGInterpolationNone);
  CGColorSpaceRelease(colorSpace);
  CGContextTranslateCTM(bmContext,
                        +(rotatedRect.size.width/2),
                        +(rotatedRect.size.height/2));
  CGContextRotateCTM(bmContext, angleInRadians);
  CGContextTranslateCTM(bmContext,
                        -(rotatedRect.size.width/2),
                        -(rotatedRect.size.height/2));
  CGContextDrawImage(bmContext, CGRectMake(0, 0,
                                           rotatedRect.size.width,
                                           rotatedRect.size.height),
                     imgRef);

  CGImageRef rotatedImage = CGBitmapContextCreateImage(bmContext);
  CFRelease(bmContext);
  [(id)rotatedImage autorelease];

return rotatedImage;
}

- (CGImageRef)CGImageRotatedByAngle:(CGImageRef)imgRef angle:(CGFloat)angle
{
  CGFloat angleInRadians = angle * (M_PI / 180);
  CGFloat width = CGImageGetWidth(imgRef);
  CGFloat height = CGImageGetHeight(imgRef);

  CGRect imgRect = CGRectMake(0, 0, width, height);
  CGAffineTransform transform = CGAffineTransformMakeRotation(angleInRadians);
  CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, transform);

  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef bmContext = CGBitmapContextCreate(NULL,
                                                 rotatedRect.size.width,
                                                 rotatedRect.size.height,
8,
0,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedFirst);
  CGContextSetAllowsAntialiasing(bmContext, FALSE);
  CGContextSetInterpolationQuality(bmContext, kCGInterpolationNone);
  CGColorSpaceRelease(colorSpace);
  CGContextTranslateCTM(bmContext,
                        +(rotatedRect.size.width/2),
                        +(rotatedRect.size.height/2));
  CGContextRotateCTM(bmContext, angleInRadians);
  CGContextTranslateCTM(bmContext,
                        -(rotatedRect.size.width/2),
                        -(rotatedRect.size.height/2));
  CGContextDrawImage(bmContext, CGRectMake(0, 0,
                                           rotatedRect.size.width,
                                           rotatedRect.size.height),
                     imgRef);

  CGImageRef rotatedImage = CGBitmapContextCreateImage(bmContext);
  CFRelease(bmContext);
  [(id)rotatedImage autorelease];

return rotatedImage;
}