iphone - iOS : Save image with custom resolution

Question

Hi I am try to capture a view then save as an image into Photo Library , but I need create a custom resolution for captured image , here is my code but when app saves the images the resolution is low !

UIGraphicsBeginImageContextWithOptions(self.captureView.bounds.size, self.captureView.opaque, 0.0);

[self.captureView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * screenshot = UIGraphicsGetImageFromCurrentImageContext();

CGRect cropRect = CGRectMake(0 ,0 ,1435 ,1435);
CGImageRef imageRef = CGImageCreateWithImageInRect([screenshot CGImage], cropRect);
CGImageRelease(imageRef);

UIImageWriteToSavedPhotosAlbum(screenshot , nil, nil, nil);

UIGraphicsEndImageContext();

but the resolution in iPhone is : 320 x 320 and retina is : 640 x 640

I would be grateful if you help me to fix this issue .

Answer 1

Your code is pretty close. What you need to do is re-render the screenshot at the custom resolution. I modified your code to do this:

UIView* captureView = self.view;

/* Capture the screen shoot at native resolution */
UIGraphicsBeginImageContextWithOptions(captureView.bounds.size, captureView.opaque, 0.0);
[captureView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * screenshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

/* Render the screen shot at custom resolution */
CGRect cropRect = CGRectMake(0 ,0 ,1435 ,1435);
UIGraphicsBeginImageContextWithOptions(cropRect.size, captureView.opaque, 1.0f);
[screenshot drawInRect:cropRect];
UIImage * customScreenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

/* Save to the photo album */
UIImageWriteToSavedPhotosAlbum(customScreenShot , nil, nil, nil);

Note that if capture view is not square then the image will be distorted. The saved image will always be square and 1435x1435 pixels.