Why PNG image got double size after taking screenshot of UIView?

Question

I am able to take screenshot from UIView at iPhone 6 with below code: -

Here I have printed 2 logs. First gives me image size {375, 667} but after converting it to PNG format it gives me image size {750, 1334}.

I know that it's converting it for the retina display. Each point is represented by 2 pixels on the screen so the saved image is double the resolution.

But I need image size {375, 667} with PNG format.

- (UIImage *)imageWithView:(UIView *)view {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, NO, [UIScreen mainScreen].scale);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    NSLog(@"Image Size: %@", image);  // Image Size: <UIImage: 0x1700880c0>, {375, 667}

    NSData* imageData =  UIImagePNGRepresentation(image);
    UIImage* pngImage = [UIImage imageWithData:imageData];
    UIImageWriteToSavedPhotosAlbum(pngImage, nil, nil, nil);

    NSLog(@"PNG Image Size: %@", pngImage);  // PNG Image Size: <UIImage: 0x174087760>, {750, 1334}

    return image;
}

Big Image:-

Small Image:-

Possible duplicate of [iOS : Save image with custom resolution](https://stackoverflow.com/questions/11432169/ios-save-image-with-custom-resolution) — Lal Krishna, Aug 21 '17 at 05:41

score 1 · Answer 1 · answered Aug 21 '17 at 05:18

1

just to not get a bad quality you can create an image with screen scale

but when you load you can use this

CGFloat screenScale = [UIScreen mainScreen].scale;
if (screenScale != img.scale) {
    img = [UIImage imageWithCGImage:img.CGImage scale:screenScale    orientation:img.imageOrientation];
}

answered Aug 21 '17 at 05:18

Abdelahad Darwish

5,969
1
17
35

Thanks @Abdelahad Darwish. It gives me Image Size: {375, 667} in NSLog but when I am saving it using UIImageWriteToSavedPhotosAlbum then it again gives me image dimension {750, 1334} in Photos(Camera Roll). Please help. I need Image Size: {375, 667} in PNG with good quality of image. – Asif Raza Aug 21 '17 at 06:45
see your code you can compress image with this ` UIImage* pngImage = [UIImage imageWithData:imageData scale:1];` – Abdelahad Darwish Aug 21 '17 at 06:48
I tried UIImage* pngImage = [UIImage imageWithData:imageData scale:1]; but it gives same image dimension {750, 1334} in Photos(Camera Roll). – Asif Raza Aug 21 '17 at 07:02

score 0 · Answer 2 · answered Aug 21 '17 at 04:50

0

Change the scale to 1 instead of [UIScreen mainScreen].scale.

UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, 1);

answered Aug 21 '17 at 04:50

Imad Ali

3,261
1
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I have also checked with this it gives me PNG image size {375, 667} but problem is that it reduces image quality. Image got blurred. I need PNG image as same size as JPG with same quality. Please help. – Asif Raza Aug 21 '17 at 05:03
I have attached 2 images. Big with [UIScreen mainScreen].scale and small is with 1. Here I am getting quality issue in small image. – Asif Raza Aug 21 '17 at 05:12
How can I fix it also? Please help, thanks in advance. – Asif Raza Aug 21 '17 at 05:18
@AsifRaza Keep scale to original, Try this, use this method: https://stackoverflow.com/a/613380/1025063 – Imad Ali Aug 21 '17 at 05:26

Why PNG image got double size after taking screenshot of UIView?

2 Answers2