ios - 如何调整图像大小并避免图像模糊？

Question

我目前正在使用不模糊的代码，但它只是切掉了一部分，如果我尝试在线使用不同的代码，它会切掉一部分并且也变得模糊。我需要做什么，图片是 512x512，试图将其缩小到 100x100，它是 jpg。

这是我现在使用的代码:

//setting up each cell
    -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView
                     cellForItemAtIndexPath:(NSIndexPath *)indexPath
    {
        CollectionGridCell *myCell = [collectionView
                                        dequeueReusableCellWithReuseIdentifier:@"GridCell"
                                        forIndexPath:indexPath];


        long row = [indexPath row];

           NSURL *baseUrl = [NSURL URLWithString:@"http://example.com/"];

    NSString *imageItemName = [homeImages objectAtIndex:row];
    NSURL *url = [NSURL URLWithString:imageItemName relativeToURL:baseUrl];

   // NSURL *url = /* prepare a url... see note below */
    [myCell.homeImage setImageWithURL:url
                     placeholderImage:[UIImage imageNamed:@"menuButton.png"]
                            completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
                                // inspect cacheType here to make sure it's cached as you want it
                               myCell.homeImage.image = [self resizeImage:image newSize:CGSizeMake(75,75)];

                            }];

    return myCell;

}


- (UIImage *)resizeImage:(UIImage*)image newSize:(CGSize)newSize {
    CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
    CGImageRef imageRef = image.CGImage;

    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();

    // Set the quality level to use when rescaling
    CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
    CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height);

    CGContextConcatCTM(context, flipVertical);
    // Draw into the context; this scales the image
    CGContextDrawImage(context, newRect, imageRef);

    // Get the resized image from the context and a UIImage
    CGImageRef newImageRef = CGBitmapContextCreateImage(context);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

    CGImageRelease(newImageRef);
    UIGraphicsEndImageContext();

    return newImage;

}

更新:到目前为止，我尝试过的每一种方法，甚至是下面的方法，都会导致中间部分出现裁剪。我是否必须在我的代码中指定其他内容，是否有调用它以裁剪中间部分的内容？

这是我的网格单元 .h 文件:

#import <UIKit/UIKit.h>

@interface CollectionGridCell : UICollectionViewCell
@property (weak, nonatomic) IBOutlet UIImageView *homeImage;

@end

这是我的网格单元 .m 文件:

#import "CollectionGridCell.h"

@implementation CollectionGridCell

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

@end

Answer 1

无需重新调整图像大小。只需将以下属性设置为您的 ImageView 即可。

 [myCell.homeImage setImageWithURL:url
                     placeholderImage:[UIImage imageNamed:@"menuButton.png"]
                            completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
                                // inspect cacheType here to make sure it's cached as you want it
                               myCell.homeImage.image = image;
                               myCell.homeImage.contentMode = UIViewContentModeScaleAspectFit;
                            }];