使用相机拍摄的iOS裁剪图像

Question

I am using the camera ( iOS 7 , iPad mini ) to take a picture and crop it to a square. I am pretty content with the default cropping functionality I get from the following code:

    imagePickerController = [[UIImagePickerController alloc] init];
    imagePickerController.delegate = self;
    imagePickerController.mediaTypes = @[(NSString *) kUTTypeImage];
    imagePickerController.allowsEditing = YES;
    UIImage *image = info[UIImagePickerControllerEditedImage]

It gives me a squared overlay over the image I took. If I zoom, I can pan the image a little. However I am surprised I can not move the image up and down (without zoom) to move the crop rectangle over the Image. If I try to do so, it just bounces back to the original location. What am I missing? Or is this functionality just missing?

From the many questions here, most are answered with a disappointing 'It has to be done in a custom way'.

Answer 1

Here's the easiest way to do it (without reimplementing UIImagePickerController). First, use an overlay to make the camera field look square. Here's an example for 3.5" screens (you'd need to update it to work for iPhone 5):

UIImagePickerController *imagePickerController = [[UIImagePickerController alloc] init];
imagePickerController.sourceType = source;

if (source == UIImagePickerControllerSourceTypeCamera) {
    //Create camera overlay
    CGRect f = imagePickerController.view.bounds;
    f.size.height -= imagePickerController.navigationBar.bounds.size.height;
    CGFloat barHeight = (f.size.height - f.size.width) / 2;
    UIGraphicsBeginImageContext(f.size);
    [[UIColor colorWithWhite:0 alpha:.5] set];
    UIRectFillUsingBlendMode(CGRectMake(0, 0, f.size.width, barHeight), kCGBlendModeNormal);
    UIRectFillUsingBlendMode(CGRectMake(0, f.size.height - barHeight, f.size.width, barHeight), kCGBlendModeNormal);
    UIImage *overlayImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImageView *overlayIV = [[UIImageView alloc] initWithFrame:f];
    overlayIV.image = overlayImage;
    [imagePickerController.cameraOverlayView addSubview:overlayIV];
}

imagePickerController.delegate = self;
[self presentViewController:imagePickerController animated:YES completion:nil];

Then, after you get a picture back from the UIImagePickerController, crop it to a square with something like this:

//Crop the image to a square
CGSize imageSize = image.size;
CGFloat width = imageSize.width;
CGFloat height = imageSize.height;
if (width != height) {
    CGFloat newDimension = MIN(width, height);
    CGFloat widthOffset = (width - newDimension) / 2;
    CGFloat heightOffset = (height - newDimension) / 2;
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(newDimension, newDimension), NO, 0.);
    [image drawAtPoint:CGPointMake(-widthOffset, -heightOffset)
                   blendMode:kCGBlendModeCopy
                       alpha:1.];
    image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}

This is Objective c Code.