【问题标题】：How to zoom only visible image in image view not transparent part of image?如何在图像视图中仅缩放可见图像而不是图像的透明部分？
【发布时间】：2016-09-12 11:48:30
【问题描述】：

我在 UIView 中有一个 scrollView，在 ScrollView.scrollview 和 imageview 中有一个 imageView 具有相同的大小。我已将图像视图内容模式设置为 UIViewContentModeScaleAspectFit 。当我双击图像视图时，图像视图不仅缩放图像视图的可见图像，还缩放图像的透明部分。

我只想缩放图像视图的可见图像。

image_scroll = [[UIScrollView alloc] initWithFrame:CGRectMake(0,0,screen_width,550)];
self.image_view = [[UIImageView alloc] initWithFrame:CGRectMake(0,0, image_scroll.frame.size.width, image_scroll.frame.size.height)];
self.image_view.backgroundColor=[UIColor clearColor];
self.image_view.contentMode = UIViewContentModeScaleAspectFit;
self.image_view.clipsToBounds = true;
self.image_view.userInteractionEnabled = YES;
self.image_view.image=[UIImage imageNamed:@"img1.png"];
doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
[doubleTap setNumberOfTapsRequired:2];
[self.image_view addGestureRecognizer:doubleTap];
[image_scroll setMaximumZoomScale:4.0];
[image_scroll addSubview:self.image_view];


- (void)handleDoubleTap:(UIGestureRecognizer *)gestureRecognizer {

        NSLog(@"handleDoubleTap");

        float newScale = [image_scroll zoomScale] * 2.0;

        if (newScale > image_scroll.maximumZoomScale){
            newScale = image_scroll.minimumZoomScale;
            CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];

            [image_scroll zoomToRect:zoomRect animated:YES];

        }
        else{

            newScale = imageScroll.maximumZoomScale;
            CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];

            [image_scroll zoomToRect:zoomRect animated:YES];
        }
    }
}


- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center {

    CGRect zoomRect;
    // the zoom rect is in the content view's coordinates.
    //    At a zoom scale of 1.0, it would be the size of the imageScrollView's bounds.
    //    As the zoom scale decreases, so more content is visible, the size of the rect grows.
    zoomRect.size.height = [image_scroll frame].size.height / scale;
    zoomRect.size.width  = [image_scroll frame].size.width  / scale;

    // choose an origin so as to get the right center.
    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);
    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);

    return zoomRect;

}

1.原图 2.图片缩放后

提前致谢。

【问题讨论】：

我也遇到了这个问题。

标签： ios objective-c uiimageview uitapgesturerecognizer pinchzoom

【解决方案1】：

目标-C

我认为您应该检查我的演示项目： https://github.com/VivekVithlani/PinchZoom-Objective-c.git

我没有实现双击缩放，它只是捏缩放。

您的问题已解决 100%

【讨论】：