How to scale a UIImageView proportionally?

ronin_1987 0
Viewed 343386

I have a UIImageView and the objective is to scale it down proportionally by giving it either a height or width. 

UIImage *image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://farm4.static.flickr.com/3092/2915896504_a88b69c9de.jpg"]]];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; 

//Add image view
[self.view addSubview:imageView];   

//set contentMode to scale aspect to fit
imageView.contentMode = UIViewContentModeScaleAspectFit;

//change width of frame
CGRect frame = imageView.frame;
frame.size.width = 100;
imageView.frame = frame;

The image did get resized but the position is not at the top left. What is the best approach to scaling image/imageView and how do I correct the position?

objective-c cocoa-touch
17 Answers

Fixed easily, once I found the documentation!

 imageView.contentMode = .scaleAspectFit
user_2774450

I just tried this, and UIImage does not support _imageScaledToSize.

I ended up adding a method to UIImage using a category - a suggestion I found on the Apple Dev forums.

In a project-wide .h -

@interface UIImage (Extras)
- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;
@end;

Implementation:

@implementation UIImage (Extras)

- (UIImage *)imageByScalingProportionallyToSize:(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;
        else
            scaleFactor = heightFactor;

        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;
        }
    }


    // this is actually the interesting part:

    UIGraphicsBeginImageContext(targetSize);

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

    [sourceImage drawInRect:thumbnailRect];

    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

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


    return newImage ;
}

@end;
Jane_Sales_639940

You could try making the imageView size match the image. The following code is not tested.

CGSize kMaxImageViewSize = {.width = 100, .height = 100};
CGSize imageSize = image.size;
CGFloat aspectRatio = imageSize.width / imageSize.height;
CGRect frame = imageView.frame;
if (kMaxImageViewSize.width / aspectRatio <= kMaxImageViewSize.height) 
{
    frame.size.width = kMaxImageViewSize.width;
    frame.size.height = frame.size.width / aspectRatio;
} 
else 
{
    frame.size.height = kMaxImageViewSize.height;
    frame.size.width = frame.size.height * aspectRatio;
}
imageView.frame = frame;
Boot_To_The_Head_206850

This works fine for me Swift 2.x:

imageView.contentMode = .ScaleAspectFill
imageView.clipsToBounds = true;
user_16627510

UIImageView+Scale.h:

#import <Foundation/Foundation.h>

@interface UIImageView (Scale)

-(void) scaleAspectFit:(CGFloat) scaleFactor;

@end

UIImageView+Scale.m:

#import "UIImageView+Scale.h"

@implementation UIImageView (Scale)


-(void) scaleAspectFit:(CGFloat) scaleFactor{

    self.contentScaleFactor = scaleFactor;
    self.transform = CGAffineTransformMakeScale(scaleFactor, scaleFactor);

    CGRect newRect = self.frame;
    newRect.origin.x = 0;
    newRect.origin.y = 0;
    self.frame = newRect;
}

@end
user_30139920

I think you can do something like

image.center = [[imageView window] center];
user_263590

Here is how you can scale it easily.

This works in 2.x with the Simulator and the iPhone.

UIImage *thumbnail = [originalImage _imageScaledToSize:CGSizeMake(40.0, 40.0) interpolationQuality:1];
kdbdallas_267280
Related