iOS UIImage 保存质量下降？

Question

将 UIImage 保存到照片库时，我的质量似乎有所下降。任何想法如何解决它？这是重要的代码：

-(IBAction)aExportPhoto:(id)sender
{
UIImage *main = [self imageWithView:imageFrame];
UIImage *water = [self imageWithView:waterFrame];
UIImage *lign = [self imageWithView:lignFrame];

CGRect fMain = imageFrame.frame;
CGRect fWater = waterFrame.frame;
CGRect fLign = lignFrame.frame;

CGSize sMain = fMain.size;
CGSize sWater = fWater.size;
CGSize sLign = fLign.size;

UIGraphicsBeginImageContext(sMain);

[main drawInRect:CGRectMake(0, 0, sMain.width, sMain.height)];
[lign drawInRect:CGRectMake(fMain.origin.x, sMain.height - 25, sMain.width - 45, 20) blendMode:kCGBlendModeNormal alpha:1.0f];
[water drawInRect:CGRectMake(sMain.width - 45, sMain.height - 35, 40, 40) blendMode: kCGBlendModeNormal alpha: 1.0f];

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIImageWriteToSavedPhotosAlbum(newImage, nil, nil, nil);
UIGraphicsEndImageContext();

}

这是 imageWithView 方法：

- (UIImage *) imageWithView:(UIImageView *)view
{
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];

UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return img;
}

提前致谢！

Answer 1

您应该像在 imageWithView 中那样在 aExportPhoto 中使用 UIGraphicsBeginImageContextWithOptions。 UIGraphicsBeginImageContext 使用 1 的比例（非视网膜分辨率），而您想使用 0（设备的比例）。