Question

我试图将图像居中（相对于iphone屏幕），这样当加载视图时图像是中心宽度/高度...在我的情况下，我的视图被加载到像素点0,0图像本身，如果我缩小图像出现在左上角，而不是屏幕/视图的中间中心。以下是我到目前为止的情况：

UIImage *image = [UIImage imageNamed: @"t.bmp"];
self.view.backgroundColor = [UIColor blackColor];
self.mi.frame = CGRectMake(0, 0, image.size.width, image.size.height);
self.mi.contentMode = (UIViewContentModeCenter);
self.mi.backgroundColor = [UIColor blackColor];
[self.mi setImage:image];

/* Draw a line here!!
UIGraphicsBeginImageContext(self.mi.frame.size);
[self.mi.image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
CGContextSetLineWidth(context, 20.0);
CGContextBeginPath(context);
CGContextMoveToPoint(context, 0,0);
CGContextAddLineToPoint(context, 200, 200);    
CGContextMoveToPoint(context, 200,0);
CGContextAddLineToPoint(context, 0, 200);
CGContextStrokePath(context);
self.mi.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
*/

self.expimg.maximumZoomScale = 2.0;
self.expimg.minimumZoomScale = 0.1;
self.expimg.clipsToBounds = YES;
self.expimg.delegate = self;
[self.expimg setContentSize:self.mi.frame.size];

[self.expimg addSubview: self.mi];
[self.view addSubview: self.expimg];

谢谢！

编辑：mi是UIImageView，expimg是UIScrollView（使用的界面构建器）。此外，还定义了viewForZoomingInScrollView。

Answer 1

您应该可以通过调整图像的位置和大小以及初始加载时滚动视图以及缩放级别更改来实现此目的。制作一个在viewDidLoad上调用的方法，再次在UIScrollViewDelegate方法scrollViewDidZoom:上调用。

这样的东西应该可以工作（其中imageView和scrollView是类属性）：

- (void)centerImage {

    CGSize screenSize = CGSizeMake(320, 480);

    CGSize imageSize = imageView.frame.size;
    imageSize.width = imageSize.width * scrollView.zoomScale;
    imageSize.height = imageSize.height * scrollView.zoomScale;
    CGSize scrollSize = scrollView.frame.size;

    CGFloat centerX;
    CGFloat centerY;
    CGFloat left;
    CGFloat top;

    if (imageSize.width > screenSize.width) {
        scrollSize.width = imageSize.width;
        centerX = imageSize.width/2;
        left = 0;
    } else {
        scrollSize.width = screenSize.width;
        centerX = screenSize.width/2;
        left = centerX - imageSize.width/2;
    }

    if (imageSize.height > screenSize.height) {
        scrollSize.height = imageSize.height;
        centerY = imageSize.height/2;
        top = 0;
    } else {
        scrollSize.height = screenSize.height;
        centerY = screenSize.width/2;
        top = centerY - imageSize.height/2;
    }

    CGRect scrollFrame = scrollView.frame;
    scrollFrame.size = scrollSize;
    scrollView.frame = scrollFrame;

    CGRect imageFrame = imageView.frame;
    imageFrame.origin = CGPointMake(left, top);

    scrollView.contentOffset = CGPointMake(centerX-(imageSize.width/2), centerY-(imageSize.height/2));

}

我没有测试过这个，所以我的一些数学可能是错误的。无论哪种方式，它都有希望让你知道该怎么做。

Answer 2

步骤1：您创建一个图像视图属性，然后在 viewDidLoad 中初始化它并添加到scrollView：

self.pictureImage = [[UIImageView alloc]initWithImage:self.picture];
[_scrollView addSubview:_pictureImage];
self.pictureImage.alpha = 0;
_scrollView.delegate = self;

第2步：创建 adjustZoomScale 功能以获得最小比例

- (CGFloat)adjustZoomScale{
CGFloat scale = self.scrollView.bounds.size.width / self.pictureImage.bounds.size.width;
CGFloat h = scale * self.pictureImage.bounds.size.height;
if (h > self.scrollView.bounds.size.height) {
    scale = self.scrollView.bounds.size.height / self.pictureImage.bounds.size.height;
}
return scale;
}

第3步：因为滚动视图的框架将在 viewDidAppear 更新，所以我们需要在此处调整缩放比例。并设置alpha以使图像显得更流畅：

- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear: animated];
_scrollView.maximumZoomScale = 1.0;
_scrollView.minimumZoomScale = [self adjustZoomScale];
[_scrollView setZoomScale:_scrollView.minimumZoomScale];
self.pictureImage.alpha = 1;
}

步骤4：实施 viewForZoomingInScrollView （滚动委托方法）并返回图像视图

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
return self.pictureImage;
}

步骤5：实施 scrollViewDidZoom （滚动委托方法）并调整图像视图点

- (void)scrollViewDidZoom: (UIScrollView*) scrollView {
CGSize boundsSize = scrollView.bounds.size;
CGRect contentsFrame = _pictureImage.frame;

if (contentsFrame.size.width < boundsSize.width) {
    contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0;
} else {
    contentsFrame.origin.x = 0.0;
}

if (contentsFrame.size.height < boundsSize.height) {
    contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0;
} else {
    contentsFrame.origin.y = 0.0;
}
_pictureImage.frame = contentsFrame;
}

在this post感谢 shawhu ，以便在缩放时调整图像视图的点数

Answer 3

[scrollView zoomToRect：CGRectMake（x，y，width，height）animated：YES];会为你工作...... rect应该将这些中心坐标作为原点。

如何在uiimageview / uiscrollview中放大图像（缩放前后）

3 个答案: