objective-c - 在边界内旋转图像

Question

我尝试在其 super View 中旋转 ImageView ，以便该 ImageView 在旋转时始终接触 super View 的边界而不是越过它们，并适当调整大小。我该如何实现？ ImageView 应该能够 360˚ 旋转。

这里我使用基于三角形公式的计算，考虑初始 ImageView 对角线角度。

也许我应该考虑旋转后 ImageView 的新边界框(它的 x 和 y 坐标变为负数，并且变换后的帧大小也变大)。

到目前为止没有成功，我的 ImageView 尺寸缩小得太快而且太多了。因此，据我所知，我的目标是为 CGAffineTransformScale 获得适当的比例因子。也许还有其他方法可以做到这一点。

// set initial values

    _planImageView.layer.affineTransform = CGAffineTransformScale(CGAffineTransformIdentity, 1, 1);

    _degrees = 0;

    _initialWidth = _planImageView.frame.size.width;
    _initialHeight = _planImageView.frame.size.height;
    _initialAngle = MathUtils::radiansToDegrees(atan((_initialWidth / 2) / (_initialHeight / 2)));

// rotation routine

- (void)rotatePlanWithDegrees:(double)degrees
{
    double deltaDegrees = degrees - _degrees;
    _initialAngle -= deltaDegrees;
    double newAngle = _initialAngle;
    double newWidth = (_initialWidth / 2) * tan(MathUtils::degreesToRadians(newAngle)) * 2;
    double newHeight = newWidth * (_initialHeight / _initialWidth);

    NSLog(@"DEG %f DELTA %f A %f W %f H %f", degrees, deltaDegrees, newAngle, newWidth, newHeight);

    double currentScale = newWidth / _initialWidth;

    _planImageView.layer.affineTransform = CGAffineTransformScale(CGAffineTransformIdentity, currentScale, currentScale);
    _planImageView.layer.affineTransform = CGAffineTransformRotate(_planImageView.layer.affineTransform, (CGFloat) MathUtils::degreesToRadians(degrees));

    _degrees = degrees;

    self->_planImageView.center = _center;

//    NSLog(@"%@", NSStringFromCGRect(_planImageView.frame));
}

编辑

感谢答案，我重写了例程，现在它可以工作了!

- (void)rotatePlanWithDegrees:(double)degrees
{
    double newWidth =
            _initialWidth  * abs(cos(MathUtils::degreesToRadians(degrees))) +
            _initialHeight * abs(sin(MathUtils::degreesToRadians(degrees)));
    double newHeight =
            _initialWidth  * abs(sin(MathUtils::degreesToRadians(degrees))) +
            _initialHeight * abs(cos(MathUtils::degreesToRadians(degrees)));

    CGFloat scale = (CGFloat) MIN(
            self.planImageScrollView.frame.size.width / newWidth,
            self.planImageScrollView.frame.size.height / newHeight);

    CGAffineTransform rotationTransform = CGAffineTransformMakeRotation((CGFloat) MathUtils::degreesToRadians(degrees));
    CGAffineTransform scaleTransform  = CGAffineTransformMakeScale(scale, scale);
    _planImageView.layer.affineTransform = CGAffineTransformConcat(rotationTransform, scaleTransform);

    self->_planImageView.center = _center;
}

Answer 1

当您旋转矩形 W x H 时，边界框的尺寸为 W' = W |cos Θ| + H |sin Θ|, H' = W |sin Θ| + H |cos Θ|。

如果您需要将其放入 W" x H" 矩形中，则缩放因子是 W"/W' 中最小的一个> 和 H"/H'。