0
我想实现iPhone照片应用程序（默认iPhone应用程序）。当我想要加载大图像（2500 * 3700）时，我遇到了困难。当我想从一幅图像滚动到另一幅图像时，我看到了像口吃这样的东西。要显示从苹果的网站它的显示方法我用ImageScrollView图片：ImageScrollView.mUIImageView与大图像。问题
- (void)displayImage:(UIImage *)image
{
// clear the previous imageView
[imageView removeFromSuperview];
[imageView release];
imageView = nil;
// reset our zoomScale to 1.0 before doing any further calculations
self.zoomScale = 1.0;
self.imageView = [[[UIImageView alloc] initWithImage:image] autorelease];
[self addSubview:imageView];
self.contentSize = [image size];
[self setMaxMinZoomScalesForCurrentBounds];
self.zoomScale = self.minimumZoomScale;
}
- (void)setMaxMinZoomScalesForCurrentBounds
{
CGSize boundsSize = self.bounds.size;
CGSize imageSize = imageView.bounds.size;
// calculate min/max zoomscale
CGFloat xScale = boundsSize.width/imageSize.width; // the scale needed to perfectly fit the image width-wise
CGFloat yScale = boundsSize.height/imageSize.height; // the scale needed to perfectly fit the image height-wise
CGFloat minScale = MIN(xScale, yScale); // use minimum of these to allow the image to become fully visible
// on high resolution screens we have double the pixel density, so we will be seeing every pixel if we limit the
// maximum zoom scale to 0.5.
CGFloat maxScale = 1.0/[[UIScreen mainScreen] scale];
// don't let minScale exceed maxScale. (If the image is smaller than the screen, we don't want to force it to be zoomed.)
if (minScale > maxScale) {
minScale = maxScale;
}
self.maximumZoomScale = maxScale;
self.minimumZoomScale = minScale;
}
对于我的应用我有600张* 600的图片，我告诉他们第一。当用户滚动到下一个图像时，他只能看到600 * 600的图像。然后在后台I加载3600 * 3600图像
[operationQueue addOperationWithBlock:^{
UIImage *image = [self getProperBIGImage];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
ImageScrollView *scroll = [self getCurrentScroll];
[scroll displayImage:newImage];
}];
}];
我看到的，当图像的尺寸是3600 * 3600和我想显示在640×960的屏幕图像，iPhone浪费的主队列时间1秒至缩放图像，这就是为什么我在这1秒内无法滚动到下一张图像的原因。
我想缩放图像，因为我需要用户能够放大此图像。我试图使用这种方法，但这没有帮助。
我看到一些可能的解决方案：
1）在后台提供图像的缩放在UIImageView的（但我知道，那UI只能在主线程中进行更改）
2）使用 - （ UIView *）viewForZoomingInScrollView：（UIScrollView *）scrollViewCalled在开始时只显示600 * 600图像，然后加载大图像，当用户尝试缩放时（但我尝试过这样，当我尝试初始化UIImageView与bigImage然后返回这个UIImageView;我甚至不能实现它，因为我看到坏滚动视图，滚动行为是错误的（difficault解释），当我尝试返回不同的比例不同的视图）
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollViewCalled
{
if (!zooming)
{
ImageScrollView *scroll = (ImageScrollView *)scrollViewCalled;
UIImageView *imageView = (UIImageView *)[scroll imageView];
return imageView;
}
else
{
UIImageView *bigImageView = [self getBigImageView];
return bigImageView;
}
}