调整UIImage的大小并更改UIImageView的大小

Question

我有UIImageView，我有最大高度和最大宽度的值。我想要实现的是我想拍摄图像（具有任何宽高比和任何分辨率），我希望它适合边框，所以图片不会超过它们，但它可以根据需要缩小它们。 （图中标记为红色）：

现在图像正确适合所需尺寸，但我有两个担忧： 1. UIImageView与调整大小的图像的大小不相等，因此留下红色背景（我不希望这样） 2.如果图像较小，我的UIImageView的高度未调整为较小，则保持相同的高度。

这是我的代码，我知道它错了：

UIImage *actualImage = [attachmentsArray lastObject];
UIImageView *attachmentImageNew = [[UIImageView alloc] initWithFrame:CGRectMake(5.5, 6.5, 245, 134)];
attachmentImageNew.image = actualImage;
attachmentImageNew.backgroundColor = [UIColor redColor];
attachmentImageNew.contentMode = UIViewContentModeScaleAspectFit;

那么我如何动态地改变UIImageView.image的大小，而不是整个UIImageView的大小，从而使其大小完全可以调整其内容。非常感谢任何帮助，谢谢！

Answer 1

获得已调整大小的图片Get width of a resized image after UIViewContentModeScaleAspectFit的宽度和高度后，您可以调整图片大小：

imageView.frame = CGRectMake(0, 0, resizedWidth, resizedHeight);
imageView.center = imageView.superview.center;

我没有检查它是否有效，但我认为一切都会好的

Answer 2

- (UIImage *)image:(UIImage*)originalImage scaledToSize:(CGSize)size
{
    //avoid redundant drawing
    if (CGSizeEqualToSize(originalImage.size, size))
    {
        return originalImage;
    }

    //create drawing context
    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);

    //draw
    [originalImage drawInRect:CGRectMake(0.0f, 0.0f, size.width, size.height)];

    //capture resultant image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    //return image
    return image;
}

Answer 3

这是使用扩展

的Rajneesh071答案的Swift等价物

UIImage {
  func scaleToSize(aSize :CGSize) -> UIImage {
    if (CGSizeEqualToSize(self.size, aSize)) {
      return self
    }

    UIGraphicsBeginImageContextWithOptions(aSize, false, 0.0)
    self.drawInRect(CGRectMake(0.0, 0.0, aSize.width, aSize.height))
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
  }
}

用法：

let image = UIImage(named: "Icon")
item.icon = image?.scaleToSize(CGSize(width: 30.0, height: 30.0))

Answer 4

使用下面的类别，然后将Quartz中的边框应用到图像中：

[yourimage.layer setBorderColor:[[UIColor whiteColor] CGColor]];
[yourimage.layer setBorderWidth:2];

类别： 的UIImage + AutoScaleResize.h

#import <Foundation/Foundation.h>

@interface UIImage (AutoScaleResize)

- (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize;

@end

的UIImage + AutoScaleResize.m

#import "UIImage+AutoScaleResize.h"

@implementation UIImage (AutoScaleResize)

- (UIImage *)imageByScalingAndCroppingForSize:(CGSize)targetSize
{
    UIImage *sourceImage = self;
    UIImage *newImage = nil;
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;
    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;
    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

    if (CGSizeEqualToSize(imageSize, targetSize) == NO)
    {
        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;

        if (widthFactor > heightFactor)
        {
            scaleFactor = widthFactor; // scale to fit height
        }
        else
        {
            scaleFactor = heightFactor; // scale to fit width
        }

        scaledWidth  = width * scaleFactor;
        scaledHeight = height * scaleFactor;

        // center the image
        if (widthFactor > heightFactor)
        {
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5;
        }
        else
        {
            if (widthFactor < heightFactor)
            {
                thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
            }
        }
    }

    UIGraphicsBeginImageContext(targetSize); // this will crop

    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;

    [sourceImage drawInRect:thumbnailRect];

    newImage = UIGraphicsGetImageFromCurrentImageContext();

    if(newImage == nil)
    {
        NSLog(@"could not scale image");
    }

    //pop the context to get back to the default
    UIGraphicsEndImageContext();

    return newImage;
}

@end

Answer 5

如果您拥有图片的大小，为什么不将图片视图的frame.size设置为此尺寸？

EDIT ----

好的，所以看到你的评论我建议：

UIImageView *imageView;
//so let's say you're image view size is set to the maximum size you want

CGFloat maxWidth = imageView.frame.size.width;
CGFloat maxHeight = imageView.frame.size.height;

CGFloat viewRatio = maxWidth / maxHeight;
CGFloat imageRatio = image.size.height / image.size.width;

if (imageRatio > viewRatio) {
    CGFloat imageViewHeight = round(maxWidth * imageRatio);
    imageView.frame = CGRectMake(0, ceil((self.bounds.size.height - imageViewHeight) / 2.f), maxWidth, imageViewHeight);
}
else if (imageRatio < viewRatio) {
    CGFloat imageViewWidth = roundf(maxHeight / imageRatio);
    imageView.frame = CGRectMake(ceil((maxWidth - imageViewWidth) / 2.f), 0, imageViewWidth, maxHeight);
} else {
    //your image view is already at the good size
}

此代码会将图像视图的大小调整为其图像比例，并将图像视图定位到与“默认”位置相同的中心。

PS：我希望你设置imageView.layer.shouldRasterise = YES 和imageView.layer.rasterizationScale = [UIScreen mainScreen].scale;

如果你正在使用CALayer阴影效果;）它将大大提高你的UI的性能。

Answer 6

我认为你想要的是一个不同的content mode。尝试使用UIViewContentModeScaleToFill。如有必要，这将通过更改内容的宽高比来缩放内容以适合您的UIImageView的大小。

请查看官方文档中的content mode部分，以便更好地了解可用的不同内容模式（用图片说明）。

Answer 7

   if([[SDWebImageManager sharedManager] diskImageExistsForURL:[NSURL URLWithString:@"URL STRING1"]])
   {
       NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:[NSURL URLWithString:@"URL STRING1"]];

       UIImage *tempImage=[self imageWithImage:[[SDImageCache sharedImageCache] imageFromDiskCacheForKey:key] scaledToWidth:cell.imgview.bounds.size.width];
       cell.imgview.image=tempImage;

   }
   else
   {
       [cell.imgview sd_setImageWithURL:[NSURL URLWithString:@"URL STRING1"] placeholderImage:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL)
        {
            UIImage *tempImage=[self imageWithImage:image scaledToWidth:cell.imgview.bounds.size.width];
            cell.imgview.image=tempImage;
//                [tableView beginUpdates];
//                [tableView endUpdates];

        }];
   }