SCENARIO
我正在制作照片分享应用。该应用程序需要允许用户在将图像发送到服务器之前裁剪图像。我使用的UIScrollView
带有UIImageView
子视图,其中包含我希望用户裁剪的图片。
我做了什么
我尝试在StackOverflow上使用一些解决方案来完成此操作,但它们涉及在用户缩放后拍摄UIScrollView
帧的屏幕截图。这不起作用的原因是因为当用户在iPhone 5(320x320,屏幕宽度上的完美正方形)上进行屏幕截图时,当该照片上传并显示在iPhone 6 Plus(更大的屏幕尺寸)上时,图像将像素化。
问题
如何在UIScrollView
范围内放大3000x3000放大的图像并提取UIScrollView
帧尺寸(320x320)但缩放的图像到640x640 没有会丢失图像分辨率?
例证
答案 0 :(得分:2)
首先,您可以将包含UIImageView的UIScrollView子类化,启动此UIScrollView和UIImageView,为UIImageView创建一个图像实例,以便它可以显示。
- (instancetype)initWithFrame:(CGRect)frame{
self = [super initWithFrame:frame];
if (self) {
self.delegate = self;
self.maximumZoomScale = 4.0f;
self.showsHorizontalScrollIndicator = NO;
self.showsVerticalScrollIndicator = NO;
[self loadImageView:frame];
}
return self;
}
- (void) loadImageView:(CGRect) frame {
if (!_imageView) {
_imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0,(frame.size.height-frame.size.width)/2, frame.size.width, frame.size.width)];
_imageView.contentMode = UIViewContentModeScaleAspectFit;
_imageView.center = self.center;
[self addSubview:_imageView];
}
}
//call this menthod to assginment image to imageView
- (void)showImage:(UIImage*)image{
self.imageView.image = image;
[self handleImageType];
}
其次,您可以在viewForZoomingInScrollView和scrollViewDidZoom中处理,代码如下:
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return _imageView;//your imageView inside UIScrollView
}
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
CGSize boundSize = self.bounds.size;//scrollView bounds
CGFloat boundWidth = boundSize.width;
CGFloat boundHeight = boundSize.height;
CGSize imageSize = self.imageView.image.size;
CGFloat imageWidth = imageSize.width;
CGFloat imageHeight = imageSize.height;
CGFloat zoomScale = scrollView.zoomScale;
DLog(@"zoomScale === %f",zoomScale);
[self normalScaleViewDidZoom:boundWidth boundHeight:boundHeight imageWidth:imageWidth imageHeight:imageHeight scrollView:scrollView];
}
- (void)handleImageType{
CGSize imageSize = self.imageView.image.size;//imageView's image size
CGFloat imageWidth = imageSize.width;
CGFloat imageHeight = imageSize.height;
if (imageWidth > imageHeight) {
type = 1;
} else if (imageWidth < imageHeight){
type = 2;
} else if (imageWidth == imageHeight) {
type = 3;
}
}
- (void)normalScaleViewDidZoom:(CGFloat)boundWidth boundHeight:(CGFloat)boundHeight imageWidth:(CGFloat)imageWidth imageHeight:(CGFloat)imageHeight scrollView:(UIScrollView*)scrollView{
CGFloat zoomScale = scrollView.zoomScale;
if (type == 1) {
self.contentSize = CGSizeMake(boundWidth/imageHeight*imageWidth*zoomScale,boundWidth*zoomScale + (boundHeight-boundWidth));
} else if (type == 2){
self.contentSize = CGSizeMake(boundWidth*zoomScale,boundWidth/imageWidth*imageHeight*zoomScale + (boundHeight-boundWidth) );
} else if (type == 3) {
self.contentSize = CGSizeMake(boundWidth*zoomScale,boundHeight-boundWidth+boundWidth*zoomScale);
}
[self zoomCenter:scrollView];
}
- (void)zoomCenter:(UIScrollView*)scrollView{
CGFloat offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width)?(scrollView.bounds.size.width - scrollView.contentSize.width)/2 : 0.0;
CGFloat offsetY = (scrollView.bounds.size.height > scrollView.contentSize.height)?(scrollView.bounds.size.height - scrollView.contentSize.height)/2 : 0.0;
self.imageView.center = CGPointMake(scrollView.contentSize.width/2 + offsetX,scrollView.contentSize.height/2 + offsetY);
}
我已在我的项目中应用的所有上述代码,希望可能对您有用:)