如何避免使用UIImageView的contentmode UIViewContentModeScaleAspectFit保持高度恒定而损失图像质量？

Question

I am using a collectionview inside a tableview for showing images which are being downloaded asynchronously. What I need to do is to show those images without squeezing. I am keeping height of the collectionview constant, and calculating the images' sizes after they are downloaded. I am keeping content mode of the UIIamgeView UIViewContentModeScaleAspectFit. This is what I have done to achieve my intended result.

- (void)configureMediaCell:(MediaContainerViewCell *)weakCell withMediaItem:(MSZWallPostMedia *)mediaItem withDownloadImage:(UIImage *)image{
    if (mediaItem.isFrameSet == NO) {
        weakCell.isFrameSet = YES;
        weakCell.cellImageView.image = image;
        weakCell.cellImageView.contentMode = UIViewContentModeScaleAspectFit;
        CGRect frame = weakCell.cellImageView.frame;

        //Image Scaling
        CGSize scaleSize = [self imageScale:weakCell.cellImageView];

        scaleSize.width = scaleSize.width * image.size.width;
        scaleSize.height = scaleSize.height * image.size.height;
        frame.size.width = scaleSize.width;
        frame.size.height = scaleSize.height;
        weakCell.cellImageView.frame = frame;
        mediaItem.frame = frame;
        mediaItem.isFrameSet = YES;
        [weakCell.activityIndicatorView stopAnimating];
        [self.collectionView reloadItemsAtIndexPaths:@[weakCell.indexPath]];
    } else {
        [weakCell.activityIndicatorView stopAnimating];
        weakCell.cellImageView.image = image;
        weakCell.cellImageView.frame = mediaItem.frame;
        weakCell.cellImageView.contentMode = UIViewContentModeScaleAspectFit;
    }
}

For Image Scaling:

- (CGSize)imageScale : (UIImageView *)imageView {
    CGFloat sx = imageView.frame.size.width / imageView.image.size.width;
    CGFloat sy = imageView.frame.size.height / imageView.image.size.height;
    CGFloat s = 1.0;
    switch (imageView.contentMode) {
        case UIViewContentModeScaleAspectFit:
            s = fminf(sx, sy);
            return CGSizeMake(s, s);
            break;

        case UIViewContentModeScaleAspectFill:
            s = fmaxf(sx, sy);
            return CGSizeMake(s, s);
            break;

        case UIViewContentModeScaleToFill:
            return CGSizeMake(sx, sy);

        default:
            return CGSizeMake(s, s);
    }
}

The problem in this approach is that I get the correct widths and heights but some images are shown smaller which is obvious because I am using Aspectfit property of imageview which is shown in the attached screen.

Any help regarding this would be appreciated. I need to keep images as they are keeping height of collectionviewitem fixed and variable width.

Answer 1

If I understand you correctly. You just need to find image width/height ratio and multiply desired height.

Example:

Image

width = 30, height = 10

Cell

width = ?, height = 7

Ratio = 30 / 10

cell width = 7 * (30/10) = 21

Cell size will become (21,7)

Hope this is what you meant. But you will face the problem if the image is smaller than cell. Then it might become distorted.