I see that by default, SDWebImage use SDWebImageDecoder to decompress UIImage. AFNetworking also does this with itsImageSerializer

I'm about to detect the size and resize the image, in this callback

- (UIImage *)imageManager:(SDWebImageManager *)imageManager
 transformDownloadedImage:(UIImage *)image
                  withURL:(NSURL *)imageURL

Size

I see that the size (in byte) of the original image from the server and image saved on disk are the same. So this "decompression" does not increase the file size

Resize

I follow Image Resizing Techniques, using UIGraphicsBeginImageContextWithOptions & UIImage -drawInRect: approach, with half CGRect as the original transformDownloadedImage

However, I see that

• The resized image is the same size (in dimension) as the transformDownloadedImage
• The size (in byte) of the resized image is of much smaller size than the transformDownloadedImage (80KB compared to 2.5MB)

Size (in byte) detection

I use Get size of a UIImage (bytes length) not height and width
However, I see that

• The size (in byte) is not correct

If I use normal [UIImage imageNamed:"file_name"], then all is correct. So there must be something about the "SDWebImageDecoder decompression" that make all of this fails, or my images contain unrelated image meta data

I'd like to know, thanks