CODEWITHSUNDEEP
iosobjective-cimage
user1904273
user1904273

Reputation: 4764

IOS/Objective-C: Reduce file size of pngs for thumbnails

I allow users to take a profile pic and then I need to upload it to the server. The iPhone pics are large in file size...much larger than needed for a profile pic and they take up a lot of space on the phone and also take a long time to upload to the server. I'm finding that on occasion if there is a weak Internet connection, the server times out half way through the upload.

I have code in a category to decrease the height and width of the image size but it does not seem to decrease the actual file size.

Can anyone suggest a lite way to do this--ideally without using a heavy library. Also, I'd like to avoid converting to jpg which I know allows for lossy compression.

Thanks.

Edit:

The problem might also be with how I work with the thumbnail after creating it below so I a including that code as well.

Here is code I am using to decrease height and width but it does not appear to reduce size in bytes.

@implementation UIImage (Thumbnail)
-(UIImage *) createThumbnailToFillSize:(CGSize)size
{
    CGSize mainImageSize = size;
    UIImage *thumb;

    CGFloat widthScaler = size.width / mainImageSize.width;
    CGFloat heightScaler = size.height / mainImageSize.height;

    CGSize repositionedMainImageSize = mainImageSize;

    CGFloat scaleFactor;
    // Determine if we should shrink based on width or hight
    if(widthScaler > heightScaler)
    {
        // calculate based on width scaler
        scaleFactor = widthScaler;
        repositionedMainImageSize.height = ceil(size.height / scaleFactor);
    }
    else {
        // calculate based on height scaler
        scaleFactor = heightScaler;
        repositionedMainImageSize.width = ceil(size.width / heightScaler);
    }

    UIGraphicsBeginImageContext(size);

    CGFloat xInc = ((repositionedMainImageSize.width-mainImageSize.width) / 2.f) *scaleFactor;
    CGFloat yInc = ((repositionedMainImageSize.height-mainImageSize.height) / 2.f) *scaleFactor;

    [self drawInRect:CGRectMake(xInc, yInc, mainImageSize.width * scaleFactor, mainImageSize.height * scaleFactor)];
    thumb = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();


    return thumb;
}



   //Display image in viewdidload by calling above method:

      UIImage *chosenImage = [self loadImageNamed:picname];
            CGFloat side = 150;
            side *=[[UIScreen mainScreen] scale];
            UIImage *thumbnail = [chosenImage createThumbnailToFillSize:CGSizeMake(side, side)];
            self.imageView.image = thumbnail;


- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    UIImage *chosenImage = info[UIImagePickerControllerEditedImage];
    self.didChange=YES;
      self.imageWasPicked = YES;//this is a dupe but used for updateButton
    self.changedPic=YES;
    [self updateSaveButton];

    self.imageView.image = chosenImage;
//Should I be putting code to make thumbnail here instead of in display?

    [picker dismissViewControllerAnimated:YES completion:NULL];

}

Upvotes: 0

Views: 493

Answers (1)

OlDor
OlDor

Reputation: 1466

If you are using UIImagePickerController in order to let the user choose a picture, make sure that you set

theImagePickerController.allowsEditing = YES;

This should already decrease the size of final image by 10-15 times.

If the received image is still too big, then here you can find some good examples of image resizing.

Upvotes: 2

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