iOS - UIImage Resize to Bigger get Blurry - ios

Question

I'm trying to resize the UIImage
Before the UIImage:
After this code and UIImage:
UIGraphicsBeginImageContext (CGPointMake(155,139));
[currentImageView.image drawInRect:CGRectMake(0,0,155,139)];
currentImageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSLog(#"get size : %#",NSStringFromCGSize(currentImageView.image.size));
NSLog: get size : {155,139}
Last, I try to restore the size by this code. but its blurry.
UIGraphicsBeginImageContext (OriginalSize);
[currentImageView.image drawInRect:CGRectMake(0,0,OriginalSize.width,OriginalSize.height)];
currentImageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSLog(#"get size : %#",NSStringFromCGSize(cnurrentImageView.image.size));
NSLog: get size : {1024,352}
What happened?
Have any suggestions and advice?

Answer 1

You are making two mistakes,
1.Reducing the image size and setting it to a larger size imageView,
this can be fixed with the code,
imageView.contentMode = UIViewContentModeScaleAspectFit;
2.You have resize the original image to a smaller size, then
resizing the smaller image to original size, this will stretch the
image.

Answer 2

FOR 1 : first step,
You can use this code so that the image quality doesn't loose:
Instead of
UIGraphicsBeginImageContext
Use
UIGraphicsBeginImageContextWithOptions(currentImageView.frame.size, NO, 0);
as the size you want is smaller and the imageview is larger so you also need to set
YourimageView.contentMode = UIViewContentModeScaleAspectFit;
For Second Step :
Use original image to resize it.